Quality of Apis mellifera honey after being used in the feeding of jandaira stingless bees (Melipona subnitida)

Wedson de Lima Tôrres João Claudio Vilvert Airton Torres Carvalho Ricardo Henrique de Lima Leite Francisco Klebson Gomes dos Santos Edna Maria Mendes Aroucha About the authors

ABSTRACT.

The aim of this study was to evaluate the physicochemical quality and bioactive compounds of Apis mellifera honey as well as the alterations in the quality of A. mellifera honey after being used in the feeding of Melipona subnitida colonies. A. mellifera honeys were collected in apiaries, homogenised and used as feed for M. subnitida bees for 30 days. Every five days, honey samples were collected and evaluated for physicochemical characteristics and bioactive compounds. The treatments consisted of natural honeys of A. mellifera and M. subnitida and honey of M. subnitida bee after being fed with A. mellifera honey (modified honey). M. subnitida bees, when fed with honey from A. mellifera, modified some of its characteristics, such as moisture, reducing sugars, diastase activity, colour and flavonoid content. Natural and modified honeys of A. mellifera were similar to each other and different from M. subnitida honey in terms of minerals, free acidity, electrical conductivity, phenolic content and antioxidant activity. Treatments were similar in terms of sucrose, insoluble matter, hydroxymethylfurfural and water activity. In general, the quality attributes of the modified honey were closer to the honey of A. mellifera than to the natural M. subnitida honey.

Keywords:
activity; bioactive compounds; meliponiculture; physicochemical characteristics; quality control; semi-arid climate

Introduction

Honey is a sweet, viscous and aromatic product, synthesised by bees after their feeding with floral nectar or other parts of plants and excretions of sucking insects, that bees collect and store in honeycombs for maturation (Belay et al., 2017Belay, A., Haki, G. D., Birringer, M., Borck, H., Addi, A., Baye, K., & Melaku, S. (2017). Rheology and botanical origin of Ethiopian monofloral honey. LWT - Food Science and Technology, 75, 393-401. doi: 10.1016/j.lwt.2016.09.021
https://doi.org/10.1016/j.lwt.2016.09.02...
; Aljohar et al., 2018Aljohar, H. I., Maher, H. M., Albaqami, J., Al-Mehaizie, M., Orfali, R., Orfali, R., & Alrubia, S. (2018). Physical and chemical screening of honey samples available in the Saudi market: An important aspect in the authentication process and quality assessment. Saudi Pharmaceutical Journal, 26(7), 932-942. doi: 10.1016/j.jsps.2018.04.013
https://doi.org/10.1016/j.jsps.2018.04.0...
; Khan et al., 2018Khan, S. U., Anjum, S. I., Rahman, K., Ansari, M. J., Khan, W. U., Kamal, S., … Khan, H. U. (2018). Honey: Single food stuff comprises many drugs. Saudi Journal of Biological Sciences, 25(2), 320-325. doi: 10.1016/j.sjbs.2017.08.004
https://doi.org/10.1016/j.sjbs.2017.08.0...
). Brazil stands out as one of the world's largest producers of honey (Requier et al., 2018Requier, F., Antúnez, K., Morales, C. L., Aldea Sánchez, P., Castilhos, D., Garrido, P. M., ... Garibaldi, L. A. (2018). Trends in beekeeping and honey bee colony losses in Latin America. Journal of Apicultural Research, 57(5), 657-662. doi: 10.1080/00218839.2018.1494919
https://doi.org/10.1080/00218839.2018.14...
). Most of Brazilian honey production is made by European honey bees (Apis mellifera) (with sting). However, on a small scale, meliponines are also responsible for honey production in Brazil, which include species of the genera Melipona, Trigona and Tetragona, also known as melipona, indigenous or stingless bees (Alves, Carvalho, Souza, Sodré, & Marchini, 2005Alves, R. M. O., Carvalho, C. A. L., Souza, B. A., Sodré, G. S., & Marchini, L. C. (2005). Características físico-químicas de amostras de mel de Melipona mandacaia Smith (Hymenoptera: Apidae). Ciência e Tecnologia de Alimentos, 25(4), 644-650. doi: 10.1590/S0101-20612005000400004
https://doi.org/10.1590/S0101-2061200500...
; Oliveira et al., 2012Oliveira, P. S., Muller, R. C. S., Dantas, K. G. F., Alves, C. N., Vasconcelos, M. A. M., & Venturiei, G. C. (2012). Ácidos fenólicos, flavonoides e atividade antioxidante em méis de Melipona fasciculata, M. flavolineata (Apidae, Meliponini) e Apis mellifera (Apidae, Apini) da Amazônia. Química Nova, 35(9), 1728-1732. doi: 10.1590/s0100-40422012000900005
https://doi.org/10.1590/s0100-4042201200...
; Pedro, 2014Pedro, S. R. (2014). The stingless bee fauna in Brazil (Hymenoptera: Apidae). Sociobiology, 61(4), 348-354. doi: 10.13102/sociobiology.v61i4.348-354
https://doi.org/10.13102/sociobiology.v6...
; Jaffé et al., 2015Jaffé, R., Pope, N., Carvalho, A. T., Maia, U. M., Blochtein, B., Carvalho, C. A. L., ... Venturieri, G. C. (2015). Bees for development: Brazilian survey reveals how to optimize stingless beekeeping. PloS one, 10(3), e0121157. doi: 10.1371/journal.pone.0130111
https://doi.org/10.1371/journal.pone.013...
).

Despite the traditional and low-tech breeding system and lower productivity in relation to other types of honey, melipona bees’ honey has a high price, mainly due to its high medicinal value (Vit, Medina, & Enríquez, 2004Vit, P., Medina, M., & Enríquez, M. E. (2004). Quality standards for medicinal uses of Meliponinae honey in Guatemala, Mexico and Venezuela. Bee world, 85(1), 2-5. doi: 10.1080/0005772x.2004.11099603
https://doi.org/10.1080/0005772x.2004.11...
; Jaffé et al., 2015Jaffé, R., Pope, N., Carvalho, A. T., Maia, U. M., Blochtein, B., Carvalho, C. A. L., ... Venturieri, G. C. (2015). Bees for development: Brazilian survey reveals how to optimize stingless beekeeping. PloS one, 10(3), e0121157. doi: 10.1371/journal.pone.0130111
https://doi.org/10.1371/journal.pone.013...
; Alvarez-Suarez et al., 2018Alvarez-Suarez, J. M., Giampieri, F., Brenciani, A., Mazzoni, L., Gasparrini, M., González-Paramás, A. M., ... Afrin, S. (2018). Apis mellifera vs Melipona beecheii Cuban polifloral honeys: A comparison based on their physicochemical parameters, chemical composition and biological properties. LWT - Food Science and Technology, 87, 272-279. doi: 10.1016/j.lwt.2017.08.079
https://doi.org/10.1016/j.lwt.2017.08.07...
). In addition, the creation and economic exploitation of stingless bees, called meliponiculture, is a highly sustainable activity that contributes to the conservation of bees and to the preservation of native plants (Vale, Gomes, Santos, & Ferreira, 2018Vale, M. A. D., Gomes, F. A., Santos, B. R. C., & Ferreira, J. B. (2018). Honey quality of Melipona sp. bees in Acre, Brazil. Acta Agronómica, 67(2), 201-207. doi: 10.15446/acag.v67n2.60836
https://doi.org/10.15446/acag.v67n2.6083...
).

Honey production is highly dependent on plant flowering, because the nectar and the pollen of the flowers provide energy and protein, respectively, which are required to feed the bees and their offspring. However, in some seasons there is not enough food in nature, either due to destruction of native forests or due to environmental conditions that disadvantage the flowering, such as water scarcity. With this, the use of maintenance artificial feeding becomes essential, in order to guarantee the expansion of the honey production due to the increase in oviposition and in the population of the colonies.

In order to evaluate honey quality, several physicochemical analyses are performed, which can be used as tools to understand honey synthesis as a result of supplementary feeding (Solayman et al., 2016Solayman, M., Islam, M. A., Paul, S., Ali, Y., Khalil, M. I., Alam, N., & Gan, S. H. (2016). Physicochemical properties, minerals, trace elements, and heavy metals in honey of different origins: a comprehensive review. Comprehensive Reviews in Food Science and Food Safety, 15(1), 219-233. doi: 10.1111/1541-4337.12182
https://doi.org/10.1111/1541-4337.12182...
). Thus, it has been determined that melipona bees fed with A. mellifera honey can bring forth honeys with physicochemical characteristics distinct from A. mellifera honeys.

The objective of this study was to evaluate the physicochemical quality and bioactive compounds of A. mellifera honey collected in apiaries in the midwestern region of Rio Grande do Norte state, in Brazil, and to evaluate the changes in the quality attributes of the A. mellifera honey after being used in melipona bee (M. subnitida) feeding.

Material and methods

Sample collection and treatments

Firstly, A. mellifera honey samples of 500 g each were collected in 12 apiaries in the State of Rio Grande do Norte, Brazil, and transported to the Food Engineering Laboratory of Federal Rural University of the Semi-arid Region. All 12 samples were combined and homogenised together. A part of the samples was taken for the quality analyses, whilst the other part was used for the feeding of M. subnitida bees. The artificial feeding of bees M. subnitida was carried out with A. mellifera honey, in a meliponary in Mossoró, Rio Grande do Norte state (05º 12' 13" S and 37º 19' 44" W).

The experiment was conducted in two years (2016 and 2017), using a randomised complete block design, with three replicates, each one corresponding to one bee colony. The treatments consisted of (1) natural M. subnitida honey, without artificial supply of A. mellifera honey; (2) modified A. mellifera honey, that is, honey from M. subnitida bees fed exclusively with A. mellifera honey; and (3) natural A. mellifera honey previously collected.

For M. subnitida colonies (treatments 1 and 2), pollen and wax were placed for construction of new honey storage pots by the bees. Five days later, the food induction of treatment 2 was performed, placing in each colony a plastic pot of A. mellifera honey. In treatment 1, bees were fed only by forage (nectar and pollen from blooming wild plants). Five days after feeding, the collections were started, performed within this interval up to 30 days. On the day of collection, food was replenished for treatment 2. This interval of five days was chosen according to the amount of time required for complete consumption of the quantity of food provided at each feeding by the M. subnitida bee, defined in a preliminary feeding test. After collection, the honey samples were transported to the laboratory for analysis. All samples were evaluated in duplicate.

Determination of physicochemical attributes

Moisture

Moisture of the honey samples was measured by the refractometric method, according to the method of the International Honey Commission (Bogdanov, 2009Bogdanov, S. (2009). Harmonised methods of the international honey commission. Mühlethurnen, CH: International Honey Comission.). The results were expressed in % (w w-1).

Reducing sugars and sucrose content

Reducing sugars (RS) were determined by the Lane-Eynon method, involving the reduction of Fehling's solution by titration at the boiling point against a diluted honey solution (1%, w v-1) with methylene blue (0.2%) as an internal indicator (Bogdanov, 2009Bogdanov, S. (2009). Harmonised methods of the international honey commission. Mühlethurnen, CH: International Honey Comission.). The results were expressed in % (w v-1).

Sucrose content was determined after inversion of honey solution (1%) with hydrochloric acid, water-bath heating at 80ºC and neutralisation with sodium hydroxide. Results were expressed in % (w v-1).

Insoluble matter

The insoluble matter content was determined by gravimetry, which is based on the insolubility of wax, pollen grains and other components of honey sediment (Codex Alimentarius, 2001Codex Alimentarius. (2001). Codex standard for honey. Rome, IT: FAO.).

Mineral content

Mineral content (ash) was determined by the calcination method in a muffle at 550ºC until reaching a constant weight, according to the method no. 942.05 of Association of Official Analytical Chemists (AOAC, 2012Association of Official Analytical Chemists [AOAC]. (2012). Official Methods of Analysis (19th ed.). Washington, DC: AOAC.).

Free acidity

Free acidity of honey was determined by the titrimetric method no. 962.19 of AOAC (2012). The neutralisation of the honey solution was carried out using sodium hydroxide solution, with values expressed in meq kg-1.

Diastase activity

Diastase activity was determined by the Schade procedure (Schade, Marsh, & Eckert, 1958Schade, J. E., Marsh, G. L., & Eckert, J. E. (1958). Diastase activity and hydroxyl-methyl-furfural in honey and their usefulness in detecting heat alteration. Journal of Food Science, 23(5), 446-463. doi: 10.1111/j.1365-2621.1958.tb17592.x
https://doi.org/10.1111/j.1365-2621.1958...
), based on the principle that the enzyme in the honey samples under standard conditions acts upon a standard starch solution and is capable of developing, with iodine, a colour in a defined range of intensity (Sajid, Yasmin, Asad, & Qamer, 2019Sajid, M., Yamin, M., Asad, F., Yaqub, S., Ahmad, S., Mubarik, M. A. M. S., … Qamer, S. (2019). Comparative study of physio-chemical analysis of Fresh and Branded honeys from Pakistan. Saudi Journal of Biological Sciences, 1-4. doi: 10.1016/j.sjbs.2019.06.014
https://doi.org/10.1016/j.sjbs.2019.06.0...
). This colouration was measured spectrophotometrically at 660 nm at defined time intervals and the results were expressed in Goethe units (Sakač & Sak-Bosnar, 2012Sakač, N., & Sak-Bosnar, M. (2012). A rapid method for the determination of honey diastase activity. Talanta, 93, 135-138. doi: 10.1016/j.talanta.2012.01.063
https://doi.org/10.1016/j.talanta.2012.0...
).

Hydroxymethylfurfural

The hydroxymethylfurfural (HMF) content was determined after clarifying samples with Carrez reagents and adding sodium bisulphate, according to method no. 980.23 of AOAC (2012Association of Official Analytical Chemists [AOAC]. (2012). Official Methods of Analysis (19th ed.). Washington, DC: AOAC.). The absorbance was measured spectrophotometrically at 284 and 336 nm, and results were expressed in mg kg-1.

Water activity, electrical conductivity and colour

Water activity (Aw) was measured using an ITK Wuxi Hake Apparatus (model HD-3A) previously calibrated with a sodium chloride solution. The measurement was made in a honey sample of 7.5 g, and results were expressed on a scale of 0-1.

Electrical conductivity was measured with a Tecnopon conductometer (model mCA 150). Results were expressed in μS cm-1.

The colour of the honey samples was determined by spectrophotometry and expressed on the Pfund scale, which ranks the honey in seven colours, ranging from white to dark amber.

Determination of bioactive compounds and antioxidant activity

Bioactive compounds were evaluated according to the methodologies described by Meda, Lamien, Romito, Millogo and Nacoulma (2005Meda, A., Lamien, C. E., Romito, M., Millogo, J., & Nacoulma, O. G. (2005). Determination of the total phenolic, flavonoid and proline contents in Burkina Fasan honey, as well as their radical scavenging activity. Food Chemistry, 91, 571-577. doi: 10.1016/j.foodchem.2004.10.006
https://doi.org/10.1016/j.foodchem.2004....
): total phenolic content, with results expressed in mg of gallic acid equivalents (GAE) per 100 g of honey; total flavonoid content, with the flavonoid content expressed as mg of quercetin equivalents (QE) per 100 g of honey; and antioxidant activity of honey samples, tested against the stable DPPH (2,2-diphenyl-1-picrylhydrazyl) free-radical, with results expressed as IC50, which corresponds to the antioxidant concentration required to scavenge DPPH free-radical by 50%.

Since the data obtained for all variables were consistent over the two-year period, only the average values of all harvests were subjected to the analysis of variance, and the averages of treatments were compared by Tukey’s test, at 5% probability. Also, values of physicochemical analysis were compared with those indicated in Brazilian (Instrução Normativa n. 11, 2000Instrução Normativa n. 11, de 20 de outubro de 2000 (2000). Regulamento técnico de identidade e qualidade do mel. Brasília, DF: Ministério da Agricultura e Abastecimento.) and international (Codex Alimentarius, 2001Codex Alimentarius. (2001). Codex standard for honey. Rome, IT: FAO.) legislations for quality control of A. mellifera honey. For M. subnitida honeys, however, there is no legislation for quality identification. Therefore, their physicochemical attributes were compared with parameters proposed in Brazil for stingless bee’ honey, suggested by Villas-Bôas and Malaspina (2005Villas-Bôas, J. K., & Malaspina, O. (2005). Parâmetros físico-químicos propostos para o controle de qualidade do mel de abelhas indígenas sem ferrão no Brasil. Mensagem Doce, 82, 6-16. Recovered from https://www.apacame.org.br/mensagemdoce/82/artigo2.htm
https://www.apacame.org.br/mensagemdoce/...
) and Camargo, Oliveira and Berto (2017Camargo, R. C. R., Oliveira, K. L., & Berto, M. I. (2017). Mel de abelhas sem ferrão: proposta de regulamentação. Brazilian Journal of Food Technology, 20, e2016157. doi: 10.1590/1981-6723.15716
https://doi.org/10.1590/1981-6723.15716...
), and for melipona bees’ honeys in Guatemala, Mexico and Venezuela (Vit et al., 2004Vit, P., Medina, M., & Enríquez, M. E. (2004). Quality standards for medicinal uses of Meliponinae honey in Guatemala, Mexico and Venezuela. Bee world, 85(1), 2-5. doi: 10.1080/0005772x.2004.11099603
https://doi.org/10.1080/0005772x.2004.11...
) (Table 1).

Table 1
Physicochemical analyses of honeys and limits of their results established by Brazilian and international legislations for A. mellifera honey and by two proposals of regulation for stingless bees’ honey.

Results and discussion

Honey moisture content statistically differed (p < 0.05) among the treatments, with the highest moisture in M. subnitida honey (26.11%), lowest in natural A. mellifera honey (17.59%) and intermediate moisture in modified A. mellifera honey (22.89%) (Table 2). This effect is to be expected because Apis mellifera honey is denser than that of melipona, so when ingested by stingless bees, it tends to become diluted. High moisture is unfavourable to the quality of Apis mellifera honey by increasing its fermentation and deterioration processes. In Brazil, Villas-Bôas and Malaspina (2005Villas-Bôas, J. K., & Malaspina, O. (2005). Parâmetros físico-químicos propostos para o controle de qualidade do mel de abelhas indígenas sem ferrão no Brasil. Mensagem Doce, 82, 6-16. Recovered from https://www.apacame.org.br/mensagemdoce/82/artigo2.htm
https://www.apacame.org.br/mensagemdoce/...
) suggest that moisture of stingless bee honey must be less than 35%. However, Vit et al. (2004Vit, P., Medina, M., & Enríquez, M. E. (2004). Quality standards for medicinal uses of Meliponinae honey in Guatemala, Mexico and Venezuela. Bee world, 85(1), 2-5. doi: 10.1080/0005772x.2004.11099603
https://doi.org/10.1080/0005772x.2004.11...
) suggest that the moisture of honey from Guatemala, México and Venezuela may be up to 30%. The moisture content in samples of A. mellifera monofloral honey varied from 14.1 to 20.5% (El Sohaimy, Masry, & Shehata, 2015El Sohaimy, S. A., Masry, S. H. D., & Shehata, M. G. (2015). Physicochemical characteristics of honey from different origins. Annuals of Agricultural Science, 60(2), 279-287. doi: 10.1016/j.aoas.2015.10.015
https://doi.org/10.1016/j.aoas.2015.10.0...
; Belay et al., 2017Belay, A., Haki, G. D., Birringer, M., Borck, H., Addi, A., Baye, K., & Melaku, S. (2017). Rheology and botanical origin of Ethiopian monofloral honey. LWT - Food Science and Technology, 75, 393-401. doi: 10.1016/j.lwt.2016.09.021
https://doi.org/10.1016/j.lwt.2016.09.02...
). However, Silva et al. (2013Silva, T. M. S., Santos, F. P., Evangelista-Rodrigues, A., Silva, E. M. S., Silva, G. S., Novais, J. S., … Camara, C. A. (2013). Phenolic compounds, melissopalynological, physicochemical analysis and antioxidant activity of jandaíra (Melipona subnitida) honey. Journal of Food Composition and Analysis, 29(1), 10-18. doi: 10.1016/j.jfca.2012.08.010
https://doi.org/10.1016/j.jfca.2012.08.0...
) noticed that M. subnitida honey contains more moisture (22.2 to 24.4%) when compared to that of Apis mellifera.

Table 2
Moisture, reducing sugars, sucrose, insoluble matter and mineral content of natural honey samples of M. subnitida and A. mellifera and modified honey of A. mellifera.

Modified A. mellifera honey had statistically lower (p < 0.05) reducing sugar (RS) content (60.57%) than natural A. mellifera (73.41%) and M. subnitida (74.24%) honeys, whilst these two were statistically similar (p > 0.05) (Table 2). Thus, it is found that melipona bees may have reduced the RS content of the A. mellifera honey. The RS content is a physicochemical parameter that evaluates the maturity of honey, which has a minimum content of 65% recommended by Brazilian legislation and 60% by international legislation for A. mellifera honeys. For stingless bees’ honeys, a minimum content of 60% is indicated by Camargo et al. (2017Camargo, R. C. R., Oliveira, K. L., & Berto, M. I. (2017). Mel de abelhas sem ferrão: proposta de regulamentação. Brazilian Journal of Food Technology, 20, e2016157. doi: 10.1590/1981-6723.15716
https://doi.org/10.1590/1981-6723.15716...
) and 50% by Villas-Bôas and Malaspina (2005Villas-Bôas, J. K., & Malaspina, O. (2005). Parâmetros físico-químicos propostos para o controle de qualidade do mel de abelhas indígenas sem ferrão no Brasil. Mensagem Doce, 82, 6-16. Recovered from https://www.apacame.org.br/mensagemdoce/82/artigo2.htm
https://www.apacame.org.br/mensagemdoce/...
). Vit et al. (2004Vit, P., Medina, M., & Enríquez, M. E. (2004). Quality standards for medicinal uses of Meliponinae honey in Guatemala, Mexico and Venezuela. Bee world, 85(1), 2-5. doi: 10.1080/0005772x.2004.11099603
https://doi.org/10.1080/0005772x.2004.11...
) also recommend a minimum 50% value of RS for stingless bees’ honeys. Generally, stingless bee’ honeys have lower RS contents when compared to A. mellifera honey (Alves et al., 2005Alves, R. M. O., Carvalho, C. A. L., Souza, B. A., Sodré, G. S., & Marchini, L. C. (2005). Características físico-químicas de amostras de mel de Melipona mandacaia Smith (Hymenoptera: Apidae). Ciência e Tecnologia de Alimentos, 25(4), 644-650. doi: 10.1590/S0101-20612005000400004
https://doi.org/10.1590/S0101-2061200500...
). According to Khan et al. (2018Khan, S. U., Anjum, S. I., Rahman, K., Ansari, M. J., Khan, W. U., Kamal, S., … Khan, H. U. (2018). Honey: Single food stuff comprises many drugs. Saudi Journal of Biological Sciences, 25(2), 320-325. doi: 10.1016/j.sjbs.2017.08.004
https://doi.org/10.1016/j.sjbs.2017.08.0...
), the average concentration of RS of A. mellifera honeys is 76.6%. RS values ranged between 50.5 and 75.5% in melipona honeys (Souza, Marchine, Oda-Souza, Carvalho, & Alves, 2009Souza, B. A., Marchine, L. C., Oda-Souza, M., Carvalho, C. A. L., & Alves, R. M. O. (2009). Caracterização do mel produzido por espécies de Melipona Illiger, 1806 (Apidae: Meliponini) da região nordeste do Brasil: 1. Características físico-químicas. Química Nova, 32(2), 303-308. doi: 10.1590/s0100-40422009000200007
https://doi.org/10.1590/s0100-4042200900...
; Silva et al., 2013Silva, T. M. S., Santos, F. P., Evangelista-Rodrigues, A., Silva, E. M. S., Silva, G. S., Novais, J. S., … Camara, C. A. (2013). Phenolic compounds, melissopalynological, physicochemical analysis and antioxidant activity of jandaíra (Melipona subnitida) honey. Journal of Food Composition and Analysis, 29(1), 10-18. doi: 10.1016/j.jfca.2012.08.010
https://doi.org/10.1016/j.jfca.2012.08.0...
). Values of RS below 60% may be indicative of unripened Melipona honey.

Sucrose content percentage did not differ between the treatments (p > 0.05) (Table 2). Modified A. mellifera honey (7.54%) was the only one that presented values outside the 6.0% maximum established by national legislation and 5.0% by international legislation. The high content of sucrose may result from a premature harvest, when sucrose in honey has not yet been fully converted into glucose and fructose by invertase enzyme, which is secreted by bees (Singh & Singh, 2018Singh, I., & Singh, S. (2018). Honey moisture reduction and its quality. Journal of Food Science and Technology, 55(10), 3861-3871. doi: 10.1007/s13197-018-3341-5
https://doi.org/10.1007/s13197-018-3341-...
). Besides that, high sucrose contents can indicate honey adulteration by the addition of sucrose syrups (Aljohar et al., 2018Aljohar, H. I., Maher, H. M., Albaqami, J., Al-Mehaizie, M., Orfali, R., Orfali, R., & Alrubia, S. (2018). Physical and chemical screening of honey samples available in the Saudi market: An important aspect in the authentication process and quality assessment. Saudi Pharmaceutical Journal, 26(7), 932-942. doi: 10.1016/j.jsps.2018.04.013
https://doi.org/10.1016/j.jsps.2018.04.0...
). Natural honeys of M. subnitida (3.12%) and A. mellifera (3.66%) met standard requirements for sucrose content. Thus, when used to feed melipona bees, A. mellifera honey may have been added to the nectar from forage plants. Due to the short time between bees feeding and honey harvesting, the action of invertase enzyme may have been insufficient for total sucrose hydrolysis, causing it to be elevated in the modified honey. This effect may have also occurred in some samples of natural M. subnitida honey, however in smaller proportions (Mendes, Silva, Mesquita, & Maracajá, 2009Mendes, C. D. G., Silva, J. B. A. D., Mesquita, L. X. D., & Maracajá, P. B. (2009). As análises de mel: revisão. Revista Caatinga, 22(2), 7-14. Recovered from https://periodicos.ufersa.edu.br/index.php/caatinga/article/view/789
https://periodicos.ufersa.edu.br/index.p...
). In A. mellifera honey samples evaluated by El Sohaimy et al. (2015El Sohaimy, S. A., Masry, S. H. D., & Shehata, M. G. (2015). Physicochemical characteristics of honey from different origins. Annuals of Agricultural Science, 60(2), 279-287. doi: 10.1016/j.aoas.2015.10.015
https://doi.org/10.1016/j.aoas.2015.10.0...
), sucrose contents ranged from 1.34 to 3.59%. Souza et al. (2009Souza, B. A., Marchine, L. C., Oda-Souza, M., Carvalho, C. A. L., & Alves, R. M. O. (2009). Caracterização do mel produzido por espécies de Melipona Illiger, 1806 (Apidae: Meliponini) da região nordeste do Brasil: 1. Características físico-químicas. Química Nova, 32(2), 303-308. doi: 10.1590/s0100-40422009000200007
https://doi.org/10.1590/s0100-4042200900...
) observed a variation of sucrose from 0.2 to 9.0% in melipona bee honeys in the state of Bahia.

There was no significant difference in the insoluble matter (IM) content among the three types of honey evaluated (p > 0.05) (Table 2). For this physicochemical characteristic, natural (0.16% IM) and modified (0.20% IM) A. mellifera honeys are outside the standards established by national and international legislation, whose maximum IM content limit is 0.10%. Meanwhile, honey from M. subnitida (0.11% IM) meets standard requirements suggested by Villas-Bôas and Malapsino (2005Villas-Bôas, J. K., & Malaspina, O. (2005). Parâmetros físico-químicos propostos para o controle de qualidade do mel de abelhas indígenas sem ferrão no Brasil. Mensagem Doce, 82, 6-16. Recovered from https://www.apacame.org.br/mensagemdoce/82/artigo2.htm
https://www.apacame.org.br/mensagemdoce/...
) (maximum of 0.40% IM), but not by Camargo et al. (2017Camargo, R. C. R., Oliveira, K. L., & Berto, M. I. (2017). Mel de abelhas sem ferrão: proposta de regulamentação. Brazilian Journal of Food Technology, 20, e2016157. doi: 10.1590/1981-6723.15716
https://doi.org/10.1590/1981-6723.15716...
), which indicate a maximum IM value of 0.10%. IM content of honey is indicative of impurities present, such as bees' body parts (legs and wings), wax, dust and wood chips, which are undesirable (Rogers, Somerton, Rogers, & Cox, 2010Rogers, K. M., Somerton, K., Rogers, P., & Cox, J. (2010). Eliminating false positive C4 sugar tests on New Zealand Manuka honey. Rapid Communications in Mass Spectrometry, 24(16), 2370-2374. doi: 10.1002/rcm.4642
https://doi.org/10.1002/rcm.4642...
). When evaluating 58 samples of A. mellifera honeys, Al-Farsi et al. (2018Al-Farsi, M., Al-Belushi, S., Al-Amri, A., Al-Hadhrami, A., Al-Rusheidi, M., & Al-Alawi, A. (2018). Quality evaluation of Omani honey. Food Chemistry, 262, 162-167. doi: 10.1016/j.foodchem.2018.04.104
https://doi.org/10.1016/j.foodchem.2018....
) found values between 0.01 and 0.337% for IM. For M. subnitida honey produced in the western region of Rio Grande do Norte state, Aroucha et al. (2019Aroucha, E. M. M., Silva, M. C. P., Leite, R. H. L., Santos, F. K. G., Oliveira, V. R. L., Araújo, N. O., & Silva, K. N. O. (2019). Physicochemical, antioxidants and sensorials properties of Melipona subnitida honey after dehumidifying. Journal of Food Processing and Technology, 10(3), e1000781. doi: 10.4172/2157-7110.1000781
https://doi.org/10.4172/2157-7110.100078...
) reported an average IM value of 1.05%.

Regarding the mineral content, there were no differences between natural (0.22%) and modified (0.13%) A. mellifera honeys and M. subnitida honey (0.02%) (p > 0.05) (Table 2). All honeys comply with Brazilian legislation for A. mellifera honey and three proposals of regulation for stingless bee honey, which require mineral contents below 0.60%. Mineral content of honey is associated with the mineral nutrition of the soil, the environmental conditions and the botanical and geographical origin of the vegetables that the bees visited in search of nectar (Souza et al., 2009Souza, B. A., Marchine, L. C., Oda-Souza, M., Carvalho, C. A. L., & Alves, R. M. O. (2009). Caracterização do mel produzido por espécies de Melipona Illiger, 1806 (Apidae: Meliponini) da região nordeste do Brasil: 1. Características físico-químicas. Química Nova, 32(2), 303-308. doi: 10.1590/s0100-40422009000200007
https://doi.org/10.1590/s0100-4042200900...
; Karabagias, Badeka, Kontakos, Karabournioti, & Kontominas, 2014Karabagias, I. K., Badeka, A., Kontakos, S., Karabournioti, S., & Kontominas, M. G. (2014). Characterisation and classification of Greek pine honeys according to their geographical origin based on volatiles, physicochemical parameters and chemometrics. Food Chemistry, 146, 548-557. doi: 10.1016/j.foodchem.2013.09.105
https://doi.org/10.1016/j.foodchem.2013....
). In eight A. mellifera honey samples from Morocco, El-Haskoury, Kriaa, Lyoussi and Makni (2018El-Haskoury, R., Kriaa, W., Lyoussi, B., & Makni, M. (2018). Ceratonia siliqua honeys from Morocco: Physicochemical properties, mineral contents, and antioxidant activities. Journal of Food and Drug Analysis, 26(1), 67-73. doi: 10.1016/j.jfda.2016.11.016
https://doi.org/10.1016/j.jfda.2016.11.0...
) found a variation from 0.13 to 0.69% in their mineral content.

Free acidity did not differ between the different types of honey (p > 0.05) (Table 3). Both natural (47.47 meq kg-1) and modified (41.01 meq kg-1) A. mellifera honey and M. subnitida honey (22.88 meq kg-1) were within the maximum limit of 50 meq kg-1 established by Brazilian and international legislation and legislative proposal for stingless bees' honey by Camargo et al. (2017Camargo, R. C. R., Oliveira, K. L., & Berto, M. I. (2017). Mel de abelhas sem ferrão: proposta de regulamentação. Brazilian Journal of Food Technology, 20, e2016157. doi: 10.1590/1981-6723.15716
https://doi.org/10.1590/1981-6723.15716...
). Silva et al. (2013Silva, T. M. S., Santos, F. P., Evangelista-Rodrigues, A., Silva, E. M. S., Silva, G. S., Novais, J. S., … Camara, C. A. (2013). Phenolic compounds, melissopalynological, physicochemical analysis and antioxidant activity of jandaíra (Melipona subnitida) honey. Journal of Food Composition and Analysis, 29(1), 10-18. doi: 10.1016/j.jfca.2012.08.010
https://doi.org/10.1016/j.jfca.2012.08.0...
) found variations between 24.66 and 58.33 meq kg-1 in nine M. subnitida honey samples. Free acidity is an important parameter for evaluation of honey quality, whose high values indicate possible deterioration of honey and the fermentation of sugars into organic acids (Silva, Gauche, Gonzaga, Costa, & Fett, 2016Silva, P. M., Gauche, C., Gonzaga, L. V., Costa, A. C. O., & Fett, R. (2016). Honey: Chemical composition, stability and authenticity. Food Chemistry, 196, 309-323. doi: 10.1016/j.foodchem.2015.09.051
https://doi.org/10.1016/j.foodchem.2015....
).

Table 3
Free acidity, diastase activity, hydroximethylfurfural, electrical conductivity, water activity and pH of natural honey samples of M. subnitida and A. mellifera and modified honey of A. mellifera.

Natural A. mellifera (15.05 Goethe units) and M. subnitida (10.44 DN) honeys presented similar diastase activity (p > 0.05), which is larger than that of modified A. mellifera honey (6.48 Goethe units) (p < 0.05) (Table 3). Thus, modified honey would not be approved by Brazilian legislation in this parameter, in view of the minimum requirement of 8 Goethe units. In contrast, international legislation is less stringent for this parameter, requiring a minimum value of 3 Goethe units, a value reached by all honeys. Villas-Bôas and Malaspina (2005Villas-Bôas, J. K., & Malaspina, O. (2005). Parâmetros físico-químicos propostos para o controle de qualidade do mel de abelhas indígenas sem ferrão no Brasil. Mensagem Doce, 82, 6-16. Recovered from https://www.apacame.org.br/mensagemdoce/82/artigo2.htm
https://www.apacame.org.br/mensagemdoce/...
) suggest for Brazilian stingless bees' honey the same minimum diastase activity of 3 Goethe units, the same that Vit et al. (2004Vit, P., Medina, M., & Enríquez, M. E. (2004). Quality standards for medicinal uses of Meliponinae honey in Guatemala, Mexico and Venezuela. Bee world, 85(1), 2-5. doi: 10.1080/0005772x.2004.11099603
https://doi.org/10.1080/0005772x.2004.11...
) recommend for honey from Guatemala, Mexico and Venezuela.

The diastase enzyme, also known as α-amylase, is responsible for starch hydrolysis, being related to the digestion of pollen (Silva et al., 2016Silva, P. M., Gauche, C., Gonzaga, L. V., Costa, A. C. O., & Fett, R. (2016). Honey: Chemical composition, stability and authenticity. Food Chemistry, 196, 309-323. doi: 10.1016/j.foodchem.2015.09.051
https://doi.org/10.1016/j.foodchem.2015....
). This enzyme presents a high degree of instability when subjected to high temperatures, being an important characteristic in the determination of honey freshness, since it indicates whether it was heated or adulterated (Nordin, Sainik, Chowdhury, Saim, & Idrus, 2018Nordin, A., Sainik, N. Q. A. V., Chowdhury, S. R., Saim, A. B., & Idrus, R. B. H. (2018). Physicochemical properties of stingless bee honey from around the globe: A comprehensive review. Journal of Food Composition and Analysis, 73, 91-102. doi: 10.1016/j.jfca.2018.06.002
https://doi.org/10.1016/j.jfca.2018.06.0...
).

Differing from the high values of diastase activity observed in this study, several authors reported low or non-existent diastase activity in stingless bee honey (Souza et al., 2009Souza, B. A., Marchine, L. C., Oda-Souza, M., Carvalho, C. A. L., & Alves, R. M. O. (2009). Caracterização do mel produzido por espécies de Melipona Illiger, 1806 (Apidae: Meliponini) da região nordeste do Brasil: 1. Características físico-químicas. Química Nova, 32(2), 303-308. doi: 10.1590/s0100-40422009000200007
https://doi.org/10.1590/s0100-4042200900...
; Chuttong, Chanbang, Sringarm, & Burgett, 2016Chuttong, B., Chanbang, Y., Sringarm, K., & Burgett, M. (2016). Physicochemical profiles of stingless bee (Apidae: Meliponini) honey from South east Asia (Thailand). Food Chemistry, 192, 149-155. doi: 10.1016/j.foodchem.2015.06.089
https://doi.org/10.1016/j.foodchem.2015....
). Therefore, low diastase activity in stingless bee honey can be an inherent characteristic of these species, and not an indicator of low quality. In A. mellifera honey samples from Pakistan, Sajid et al. (2019Sajid, M., Yamin, M., Asad, F., Yaqub, S., Ahmad, S., Mubarik, M. A. M. S., … Qamer, S. (2019). Comparative study of physio-chemical analysis of Fresh and Branded honeys from Pakistan. Saudi Journal of Biological Sciences, 1-4. doi: 10.1016/j.sjbs.2019.06.014
https://doi.org/10.1016/j.sjbs.2019.06.0...
) detected values between 26.97 and 43.47 Goethe units. The use of diastase activity as an indicator of honey quality is questioned by White (1994White, J. W. (1994). The role of HMF and diastase assays in quality evaluation. Bee World, 75(3), 104-117. doi: 10.1080/0005772x.1994.11099213), who points out great variation in the amount of diastase in freshly collected and unheated A. mellifera honey samples.

In relation to HMF content, there was no statistical difference between natural A. mellifera (26.92 mg kg-1) and M. subnitida (11.03 mg kg-1) honeys and modified A. mellifera honey (27.49 mg kg-1) (Table 3). Thus, for this characteristic, M. subnitida bee did not affect the A. mellifera honey. All honeys comply with Brazilian (maximum value of 60 mg kg-1) and international (maximum value of 80 mg kg-1) legislations. For stingless bee honey, Camargo et al. (2017Camargo, R. C. R., Oliveira, K. L., & Berto, M. I. (2017). Mel de abelhas sem ferrão: proposta de regulamentação. Brazilian Journal of Food Technology, 20, e2016157. doi: 10.1590/1981-6723.15716
https://doi.org/10.1590/1981-6723.15716...
) and Vit et al. (2004Vit, P., Medina, M., & Enríquez, M. E. (2004). Quality standards for medicinal uses of Meliponinae honey in Guatemala, Mexico and Venezuela. Bee world, 85(1), 2-5. doi: 10.1080/0005772x.2004.11099603
https://doi.org/10.1080/0005772x.2004.11...
) propose maximum limits of 20 mg kg-1, whilst Villas-Bôas and Malaspina (2005Villas-Bôas, J. K., & Malaspina, O. (2005). Parâmetros físico-químicos propostos para o controle de qualidade do mel de abelhas indígenas sem ferrão no Brasil. Mensagem Doce, 82, 6-16. Recovered from https://www.apacame.org.br/mensagemdoce/82/artigo2.htm
https://www.apacame.org.br/mensagemdoce/...
) indicate a maximum HMF content of 40 mg kg-1.

HMF content in honey can be affected by several factors, such as acidity, water content and minerals, and its concentration is increased by inadequate storage conditions and excessive heat treatment, being indicative of honey deterioration (Önür et al., 2018Önür, İ., Misra, N. N., Barba, F. J., Putnik, P., Lorenzo, J. M., Gökmen, V., & Alpas, H. (2018). Effects of ultrasound and high pressure on physicochemical properties and HMF formation in Turkish honey types. Journal of Food Engineering, 219, 129-136. doi: 10.1016/j.jfoodeng.2017.09.019
https://doi.org/10.1016/j.jfoodeng.2017....
). Al-Farsi et al. (2018Al-Farsi, M., Al-Belushi, S., Al-Amri, A., Al-Hadhrami, A., Al-Rusheidi, M., & Al-Alawi, A. (2018). Quality evaluation of Omani honey. Food Chemistry, 262, 162-167. doi: 10.1016/j.foodchem.2018.04.104
https://doi.org/10.1016/j.foodchem.2018....
) reported a large variation in the HMF levels of 58 samples of A. mellifera honey produced in Oman, ranging from 0 to 1062 mg kg-1. Finola, Lasagno and Marioli (2007Finola, M. S., Lasagno, M. C., & Marioli, J. M. (2007). Microbiological and chemical characterization of honeys from central Argentina. Food Chemistry, 100, 1649-1653. doi: 10.1016/j.foodchem.2005.12.046
https://doi.org/10.1016/j.foodchem.2005....
) detected in A. mellifera honeys from Argentina HMF levels between 1.1 and 44.8 mg kg-1, values close to those detected in A. mellifera honey in the present study. In honeys produced by five species of the genus Melipona, Souza et al. (2009Souza, B. A., Marchine, L. C., Oda-Souza, M., Carvalho, C. A. L., & Alves, R. M. O. (2009). Caracterização do mel produzido por espécies de Melipona Illiger, 1806 (Apidae: Meliponini) da região nordeste do Brasil: 1. Características físico-químicas. Química Nova, 32(2), 303-308. doi: 10.1590/s0100-40422009000200007
https://doi.org/10.1590/s0100-4042200900...
) found variation between 0.0 and 60.2 mg kg-1 in HMF content.

Electrical conductivity (EC) of natural (469.7 μS cm-1) and modified (511.90 μS cm-1) A. mellifera honeys was similar (p > 0.05), and both were larger than that of M. subnitida honey (77.49 μS cm-1) (p < 0.05) (Table 3). This behaviour indicates that the characteristics of natural A. mellifera were preserved in the modified honey. Brazilian legislation does not present reference values for this characteristic, whilst the international legislation establishes the maximum value of 800 μS cm-1, a requirement met by all honeys. The EC of honey is usually positively correlated with its mineral content (Karabagias et al., 2014Karabagias, I. K., Badeka, A., Kontakos, S., Karabournioti, S., & Kontominas, M. G. (2014). Characterisation and classification of Greek pine honeys according to their geographical origin based on volatiles, physicochemical parameters and chemometrics. Food Chemistry, 146, 548-557. doi: 10.1016/j.foodchem.2013.09.105
https://doi.org/10.1016/j.foodchem.2013....
). Thus, the results found in our study correlate with those of Silva et al. (2016Silva, P. M., Gauche, C., Gonzaga, L. V., Costa, A. C. O., & Fett, R. (2016). Honey: Chemical composition, stability and authenticity. Food Chemistry, 196, 309-323. doi: 10.1016/j.foodchem.2015.09.051
https://doi.org/10.1016/j.foodchem.2015....
), who indicate that the higher mineral content, the higher the resulting conductivity.

Colour, mineral content and EC are related parameters, thus darker honeys usually have higher mineral content, which results in higher conductivity (Juan-Borrás, Domenech, Hellebrandova, & Escriche, 2014Juan-Borrás, M., Domenech, E., Hellebrandova, M., & Escriche, I. (2014). Effect of country origin on physicochemical, sugar and volatile composition of acacia, sunflower and tilia honeys. Food Research International, 60, 86-94. doi: 10.1016/j.foodres.2013.11.045
https://doi.org/10.1016/j.foodres.2013.1...
). When evaluating physicochemical characteristics of honeys produced in the state of Rio Grande do Norte, Aroucha et al. (2019Aroucha, E. M. M., Silva, M. C. P., Leite, R. H. L., Santos, F. K. G., Oliveira, V. R. L., Araújo, N. O., & Silva, K. N. O. (2019). Physicochemical, antioxidants and sensorials properties of Melipona subnitida honey after dehumidifying. Journal of Food Processing and Technology, 10(3), e1000781. doi: 10.4172/2157-7110.1000781
https://doi.org/10.4172/2157-7110.100078...
) verified an average EC of 299.62 and 238.58 μS cm-1 in M. subnitida and A. mellifera honeys, respectively.

For the water activity (Aw), there was no significant difference between the honeys (Table 3). Aw values of M. subnitida honey and natural and modified A. mellifera honeys were, respectively, 0.53, 0.63 and 0.54. Both Brazilian and international legislations for A. mellifera honey and the proposals of legislation for stingless bee honey by Villas-Bôas and Malaspina (2005Villas-Bôas, J. K., & Malaspina, O. (2005). Parâmetros físico-químicos propostos para o controle de qualidade do mel de abelhas indígenas sem ferrão no Brasil. Mensagem Doce, 82, 6-16. Recovered from https://www.apacame.org.br/mensagemdoce/82/artigo2.htm
https://www.apacame.org.br/mensagemdoce/...
) and Vit et al. (2004Vit, P., Medina, M., & Enríquez, M. E. (2004). Quality standards for medicinal uses of Meliponinae honey in Guatemala, Mexico and Venezuela. Bee world, 85(1), 2-5. doi: 10.1080/0005772x.2004.11099603
https://doi.org/10.1080/0005772x.2004.11...
) do not present critical values of Aw for their respective types of honey. In contrast, Camargo et al. (2017Camargo, R. C. R., Oliveira, K. L., & Berto, M. I. (2017). Mel de abelhas sem ferrão: proposta de regulamentação. Brazilian Journal of Food Technology, 20, e2016157. doi: 10.1590/1981-6723.15716
https://doi.org/10.1590/1981-6723.15716...
) suggest that this characteristic should be considered, and its value must be between 0.52 and 0.80. Thus, honey from M. subnitida is within the scope recommended in this regulation proposal for stingless bees.

Aw evaluates honey deterioration, indicating its propensity for microbiological activity. Aw value is reduced proportionally to the increase in the sugar concentration of the honeys, since a great part of the water molecules is linked to the sugars. The Aw needed for the growth and development of microorganisms depends on their class, being around 0.8 for yeasts and 0.9 for bacteria (Ávila, Beux, Ribani, & Zambiazi, 2018Ávila, S., Beux, M. R., Ribani, R. H., & Zambiazi, R. C. (2018). Stingless bee honey: Quality parameters, bioactive compounds, health-promotion properties and modification detection strategies. Trends in Food Science & Technology, 81, 37-50. doi: 10.1016/j.tifs.2018.09.002
https://doi.org/10.1016/j.tifs.2018.09.0...
).

The predominance of colours varied between natural A. mellifera honey (predominant light amber colour), modified A. mellifera honey (predominant dark amber colour) and natural M. subnitida honey (predominant white colour) (Table 4). The samples analysed are within the standards required by Brazilian legislation, which considers acceptable variations to be from water white to dark amber for A. mellifera honey, the same as recommended for stingless bee honey by Camargo et al. (2017Camargo, R. C. R., Oliveira, K. L., & Berto, M. I. (2017). Mel de abelhas sem ferrão: proposta de regulamentação. Brazilian Journal of Food Technology, 20, e2016157. doi: 10.1590/1981-6723.15716
https://doi.org/10.1590/1981-6723.15716...
).

Table 4
Colour, total phenolic content, total flavonoid content and antioxidant activity of natural honey samples of M. subnitida and A. mellifera and modified honey of A. mellifera.

Results showed that melipona bees modified the predominant colour of A. mellifera honey. Honey colour is an important parameter for consumers (Sajid et al., 2019Sajid, M., Yamin, M., Asad, F., Yaqub, S., Ahmad, S., Mubarik, M. A. M. S., … Qamer, S. (2019). Comparative study of physio-chemical analysis of Fresh and Branded honeys from Pakistan. Saudi Journal of Biological Sciences, 1-4. doi: 10.1016/j.sjbs.2019.06.014
https://doi.org/10.1016/j.sjbs.2019.06.0...
), being related to several factors, such as mineral and flavonoid contents (Finola et al., 2007Finola, M. S., Lasagno, M. C., & Marioli, J. M. (2007). Microbiological and chemical characterization of honeys from central Argentina. Food Chemistry, 100, 1649-1653. doi: 10.1016/j.foodchem.2005.12.046
https://doi.org/10.1016/j.foodchem.2005....
). The colour of honey may vary according to its floral origin, bee species, age and storage conditions (Aroucha et al., 2019Aroucha, E. M. M., Silva, M. C. P., Leite, R. H. L., Santos, F. K. G., Oliveira, V. R. L., Araújo, N. O., & Silva, K. N. O. (2019). Physicochemical, antioxidants and sensorials properties of Melipona subnitida honey after dehumidifying. Journal of Food Processing and Technology, 10(3), e1000781. doi: 10.4172/2157-7110.1000781
https://doi.org/10.4172/2157-7110.100078...
), besides the beekeeper’s interventions (El Sohaimy et al., 2015El Sohaimy, S. A., Masry, S. H. D., & Shehata, M. G. (2015). Physicochemical characteristics of honey from different origins. Annuals of Agricultural Science, 60(2), 279-287. doi: 10.1016/j.aoas.2015.10.015
https://doi.org/10.1016/j.aoas.2015.10.0...
). Thus, the variation observed in the colour of A. mellifera honey from light amber to dark amber may be related to the origin of honey samples, which were collected at several sites with different flowerings. In 49 samples of A. mellifera honeys from Rio Grande do Sul state, Nascimento et al. (2018Nascimento, K. S., Sattler, J. A. G., Macedo, L. F. L., González, C. V. S., Melo, I. L. P., Araújo, E. S., ... Almeida-Muradian, L. B. (2018). Phenolic compounds, antioxidant capacity and physicochemical properties of Brazilian Apis mellifera honeys. LWT - Food Science and Technology, 91, 85-94. doi: 10.1016/j.lwt.2018.01.016
https://doi.org/10.1016/j.lwt.2018.01.01...
) reported a diversity of colour, from extra white to amber. In nine M. subnitida honeys evaluated by Silva et al. (2013Silva, T. M. S., Santos, F. P., Evangelista-Rodrigues, A., Silva, E. M. S., Silva, G. S., Novais, J. S., … Camara, C. A. (2013). Phenolic compounds, melissopalynological, physicochemical analysis and antioxidant activity of jandaíra (Melipona subnitida) honey. Journal of Food Composition and Analysis, 29(1), 10-18. doi: 10.1016/j.jfca.2012.08.010
https://doi.org/10.1016/j.jfca.2012.08.0...
), one had yellow-brownish colour, whilst the others had a bright yellow colour.

Total phenolic content of natural and modified A. mellifera honey was similar (92.90 and 80.36 mg GAE per 100 g, respectively) (p > 0.05) and higher than M. subnitida honey (16.09 mg GAE per 100 g) (p < 0.05) (Table 4). Thus was observed a beneficial effect of melipona bees feeding with A. mellifera honey, since this characteristic was maintained. Concentration and type of phenolic compounds depend on the floral origin of the honey and are the main factors responsible for its biological action, including its antioxidant, antimicrobial, antiviral and anticarcinogenic activity (Kuçuk et al., 2007Kuçuk, M., Kolayli, S., Karaoglu, S., Ulusoy, E., Baltaci, C., & Candan, F. (2007). Biological activities and chemical composition of three honeys of different types from Anatolia. Food Chemistry, 100, 526-534. doi: 10.1016/j.foodchem.2005.10.010
https://doi.org/10.1016/j.foodchem.2005....
). Estevinho, Pereira, Moreira, Dias and Pereira (2008Estevinho, L., Pereira, A. P., Moreira, L., Dias, L. G., & Pereira, E. (2008). Antioxidant and antimicrobial effects of phenolic compounds extracts of Northeast Portugal honey. Food and Chemical Toxicology, 46(12), 3774-3779. doi: 10.1016/j.fct.2008.09.062
https://doi.org/10.1016/j.fct.2008.09.06...
) observed that the phenolic compound content of light honeys is lower than that of dark honeys, a characteristic also observed in this study.

Total flavonoids content of the modified A. mellifera honey was statistically higher (3.29 mg QE per 100 g) (p < 0.05) than that of A. mellifera and M. subnitida, whose contents were statistically equal (1.62 and 1.16 QE per 100 g, respectively) (p > 0.05) (Table 4). In addition to using A. mellifera honey as food, melipona bees also foraged for nectar, mixing the food served with collected nectar. Such behaviour may explain the high flavonoid increase in the modified honey (Decourtye, Mader, & Desneux, 2010Decourtye, A., Mader, E., & Desneux, N. (2010). Landscape enhancement of floral resources for honey bees in agro-ecosystems. Apidologie, 41(3), 264-277. doi: 10.1051/apido/2010024
https://doi.org/10.1051/apido/2010024...
). Flavonoids are a class of polyphenols that are present in plants and serve as self-defence. Its concentration in nectar and consequently in honey is influenced by floral origin and climatic characteristics of the honey producer region. Flavonoids are some of the compounds responsible for antioxidant activity of honey (Nayik & Nanda, 2016Nayik, G. A., & Nanda, V. (2016). A chemometric approach to evaluate the phenolic compounds, antioxidant activity and mineral content of different unifloral honey types from Kashmir, India. LWT - Food Science and Technology, 74, 504-513. doi: 10.1016/j.lwt.2016.08.016
https://doi.org/10.1016/j.lwt.2016.08.01...
). Values of flavonoids found in this study are similar to those reported by Nascimento et al. (2018Nascimento, K. S., Sattler, J. A. G., Macedo, L. F. L., González, C. V. S., Melo, I. L. P., Araújo, E. S., ... Almeida-Muradian, L. B. (2018). Phenolic compounds, antioxidant capacity and physicochemical properties of Brazilian Apis mellifera honeys. LWT - Food Science and Technology, 91, 85-94. doi: 10.1016/j.lwt.2018.01.016
https://doi.org/10.1016/j.lwt.2018.01.01...
) in A. mellifera honeys (0-2.60 mg QE per 100 g). In A. mellifera and Melipona beecheii honeys from Cuba, Alvarez-Suarez et al. (2018Alvarez-Suarez, J. M., Giampieri, F., Brenciani, A., Mazzoni, L., Gasparrini, M., González-Paramás, A. M., ... Afrin, S. (2018). Apis mellifera vs Melipona beecheii Cuban polifloral honeys: A comparison based on their physicochemical parameters, chemical composition and biological properties. LWT - Food Science and Technology, 87, 272-279. doi: 10.1016/j.lwt.2017.08.079
https://doi.org/10.1016/j.lwt.2017.08.07...
) reported average values of 2.68 and 4.19 mg QE per 100 g for flavonoids content, respectively.

Antioxidant activity of natural and modified A. mellifera honeys was statistically equal (IC50 = 59.01 and 59.77 mg mL-1, respectively) (p > 0.05) and higher than that of M. subnitida honey (IC50 = 610.31 mg mL-1) (p < 0.05) (Table 4). In this study, the results were expressed in IC50, which represents necessary antioxidant concentration to reduce the DPPH free-radical by 50%. Thus, low IC50 indicates high antioxidant activity of honey samples. In this way, a beneficial effect of stingless bee feeding with A. mellifera honey was observed, that of preserving its high antioxidant activity. Oliveira et al. (2012Oliveira, P. S., Muller, R. C. S., Dantas, K. G. F., Alves, C. N., Vasconcelos, M. A. M., & Venturiei, G. C. (2012). Ácidos fenólicos, flavonoides e atividade antioxidante em méis de Melipona fasciculata, M. flavolineata (Apidae, Meliponini) e Apis mellifera (Apidae, Apini) da Amazônia. Química Nova, 35(9), 1728-1732. doi: 10.1590/s0100-40422012000900005
https://doi.org/10.1590/s0100-4042201200...
) found a significant strong positive correlation (r = 0.87) between IC50 and total phenolic content, then honeys with higher total phenolic content and darker colouring have high antioxidant activity.

Similar results to those of this work were observed by Oliveira et al. (2012Oliveira, P. S., Muller, R. C. S., Dantas, K. G. F., Alves, C. N., Vasconcelos, M. A. M., & Venturiei, G. C. (2012). Ácidos fenólicos, flavonoides e atividade antioxidante em méis de Melipona fasciculata, M. flavolineata (Apidae, Meliponini) e Apis mellifera (Apidae, Apini) da Amazônia. Química Nova, 35(9), 1728-1732. doi: 10.1590/s0100-40422012000900005
https://doi.org/10.1590/s0100-4042201200...
), in honeys from different Amazonian locations, in which IC50 values ranged from 8.87 to 41.76 mg mL-1 for A. mellifera honeys. In contrast, the same authors observed high antioxidant activity in M. subnitida honey, with IC50 of 6.85 mg mL-1. Estevinho et al. (2008Estevinho, L., Pereira, A. P., Moreira, L., Dias, L. G., & Pereira, E. (2008). Antioxidant and antimicrobial effects of phenolic compounds extracts of Northeast Portugal honey. Food and Chemical Toxicology, 46(12), 3774-3779. doi: 10.1016/j.fct.2008.09.062
https://doi.org/10.1016/j.fct.2008.09.06...
) verified higher antioxidant activity in dark honey than in light honey.

Conclusion

When fed with A. mellifera honey, M. subnitida bee modified some physicochemical characteristics of this honey, such as moisture, reducing sugars, diastase activity and colour, in addition to the total flavonoid content. However, the final quality attributes of the modified honey were closer to the A. mellifera honey than to the natural M. subnitida honey.

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Publication Dates

  • Publication in this collection
    30 Nov 2020
  • Date of issue
    2021

History

  • Received
    15 Oct 2019
  • Accepted
    25 June 2020
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