Cold storage of peaches cv. Aurora grown in the Zona da Mata Mineira, Minas Gerais State, Brazil

Conservação refrigerada de pêssego cv. Aurora, cultivado na Zona da Mata Mineira

PLANT PRODUCTION

Cold storage of peaches cv. Aurora grown in the Zona da Mata Mineira, Minas Gerais State, Brazil¹

Conservação refrigerada de pêssego cv. Aurora, cultivado na Zona da Mata Mineira

Danielle Fabíola Pereira Silva^I; Mariana Rodrigues Ribeiro^II; José Osmar da Costa e Silva^III; Rosana Gonçalves Pires Matias^III; Claudio Horst Bruckner^IV

^IAgronomist Engineer, Doctor of Science. Departamento de Fitotecnia, Universidade Federal de Viçosa, Campus Viçosa, Avenida Peter Henry Rolfs, s/n, 36570-000, Viçosa, Minas Gerais, Brasil. [e-mail] (corresponding author). Bolsista PNPD-CAPES

^IIUndergraduate in Agronomy. Departamento de Agronomia, Universidade Federal de Viçosa, Campus Viçosa, Avenida Peter Henry Rolfs, s/n, 36570-000, Viçosa, Minas Gerais, Brasil. [e-mail]

^IIIAgronomist Engineer, Master of Science. Departamento de Fitotecnia, Universidade Federal de Viçosa, Campus Viçosa, Avenida Peter Henry Rolfs, s/n, 36570-000, Viçosa, Minas Gerais, Brasil. [e-mail]

^IVAgronomist Engineer, Doctor of Science. Departamento de Fitotecnia, Universidade Federal de Viçosa, Campus Viçosa, Avenida Peter Henry Rolfs, s/n, 36570-000, Viçosa, Minas Gerais, Brasil. [e-mail]

ABSTRACT

This study aimed to evaluate the postharvest behavior of peach cv. Aurora 1 harvested in the Zona da Mata region of Minas Gerais in two ripening stages and kept under different storage temperatures. Fruits on mid-ripe and fully ripe stages were stored at three temperatures: 5.6 ± 1.57 °C and 72.8 ± 3.8% RH; 10.4 ± 0.5 °C and 95.8 ± 5.5% RH; 21.04 ± 1.63 °C and 96.9 ± 2.6% RH up to 28 storage days (SD) . During storage, fruits stored at 21.04 ± 1.63 °C were evaluated every two days until 8 SD, and every four days for fruits stored at other temperatures. The harvest day was assigned as day zero. The variables evaluated were CO₂ production, color of the pericarp and pulp, fresh mass loss, flesh firmness, total soluble solids, titratable acidity, contents of ascorbic acid and carotenoids. The fresh mass loss increased during storage, peaking at 5.6 °C. The reduction in ascorbic acid content was higher in fully ripe fruits at all temperatures. Mid-ripe fruits reached the end of the storage period with better quality. The temperature of 10.4 °C was the most efficient in keeping postharvest quality of peach cv. Aurora 1 harvested in the Zona da Mata region.

Key words: Prunus persica, ripening stage, fruit quality.

RESUMO

Este trabalho teve como objetivo avaliar o comportamento pós-colheita de frutos de pessegueiro 'Aurora 1', colhidos na região da Zona da Mata Mineira, em dois estádios de maturação, mantidos sob diferentes temperaturas de armazenamento. Lotes de frutos nos estádios de maturação "de vez" e maduro foram armazenados em três temperaturas: 5,6 ± 1,57 °C e 72,8 ± 3,8% UR; 10,4 ± 0,5 °C e 95,8 ± 5,5% UR; 21,04 ± 1,63 °C e 96,9 ± 2,6% UR, por até 28 dias de armazenamento (DA). Durante o armazenamento, os frutos foram avaliados a cada dois dias, até o 8º DA, para frutos armazenados em 21,04 ± 1,63 °C, e a cada quatro dias, para frutos armazenados nas demais temperaturas, sendo o dia zero o dia da colheita dos frutos. Foram avaliados a produção de CO₂, a coloração do pericarpo e da polpa, a perda de massa de matéria fresca, a firmeza da polpa, o teor de sólidos solúveis, a acidez titulável, o teor de ácido ascórbico e o teor de carotenoides. A perda de matéria fresca aumentou durante o armazenamento, sendo mais acentuada na temperatura 5,6 °C. A redução do teor de ácido ascórbico foi maior nos frutos maduros, para todas as temperaturas em estudo. Frutos no estádio de maturação "de vez" chegaram ao final do período de armazenamento com melhor qualidade, sendo a temperatura de 10,4 °C a mais eficiente na manutenção da qualidade pós-colheita de frutos de pêssego 'Aurora 1', colhidos na região da Zona da Mata Mineira.

Palavras-chave: Prunus persica, estádio de amadurecimento, qualidade do fruto.

INTRODUCTION

Progress in peach genetic improvement for subtropical regions has been highly significant. As a result, the production of peaches for industry and fresh consumption extended to new areas in subtropical regions as well as the marketing period (Wagner Jr. et al., 2011).

Cultivar Aurora 1 has a low requirement of cold temperature to break dormancy (under 100 hours) and fruits of high sensory quality. Fruit is oblong shaped and weight is around 90-110 g. The skin color is red (80% color over yellow background). The flesh is firm, pale yellow, adhered to the stone. Soluble solids are, on average, 14 ° Brix, with low acidity (Cunha Júnior et al., 2007).

The ripening stage at harvest is crucial for postharvest life as well as for storage potential. Thus, when the fruits are harvested before physiological maturity they will not ripen, will become shriveled and ooze sap, or if ripening occurs, leads to a poor quality fruits. Overripe fruits deteriorate rapidly and cannot be stored and/or marketed in distant locations (Silva et al., 2012).

Chilling is among the methods used to extend the postharvest life of fruits (Silva et al., 2009). According to Souza et al. (2009), refrigerated storage slows the plant metabolism by decreasing the respiratory rate and the enzymatic activity. Peach has a climacteric respiratory pattern and after harvesting the fruit physiologically ripe, changes triggered by ethylene production and increased respiratory rate occur rapidly (Brackmann et al., 2009). Fruits of cv. Aurora 1 grown in the municipality of Taiúva - SP and stored for 35 days at 2 °C, 6 °C and 12 °C, showed no sensitivity to cold (Cunha Júnior et al., 2010).

Little is known about the effects of cold storage at different stages of maturation of peaches grown in subtropical regions. The experimental conditions used by many authors are quite varied with regard to the place of cultivation, cultivars and storage temperatures. In southern Brazil, the technology of cold storage for temperate fruits is widespread. For Minas Gerais State to gain ground in this market with efficiency, the development and improvement of farming and postharvest techniques are needed to increase shelf life and, at the same time, ensure fruit quality to the final consumer.

Thus, establishing the appropriate harvest point and optimum temperature for stone fruit storage can minimize quality loss during storage. Therefore, this study aims to evaluate the quality of peaches cv. Aurora 1 under different storage temperatures, when harvested at different ripening stages.

MATERIALS AND METHODS

Fruits of peach (cv. Aurora 1) were collected from trees growing in the municipality of Barbacena - MG (located at 21º 13' 33" S and 43º 46' 25" O, 1.164 m altitude). The climate is highland tropical (CWB), with cold winters and mild summers. The average annual temperature is 17 °C, with a maximum average of 24.17 ± 1.75 °C and minimum average of 13.58 ± 2.27 °C.

Mid-ripe and fully ripe fruits were harvested on October 25, 2011, in the early hours of the day. Visually, mid-ripe fruits were considered those with green color background and no, or little, red color covering the skin. When picked, they had coordinate b for skin color of 12.43; hue angle of 92.10 and soluble solids were 8.73 °Brix. Fully ripe peaches were considered those changing background skin color from green to creamy-white and abundant red color covering the skin (Seibert et al., 2008). When picked, they had coordinate b for skin color of 19.49; hue angle of 74.140 and soluble solids were 9.56 °Brix.

After harvest, fruits were transported in cardboard boxes, in a refrigerated car, to the laboratory of Fruit Analysis at the Universidade Federal de Viçosa - MG. Fruits were sorted and sized by suture (44.8 ± 3.6), equatorial (43.0 ± 3.9) and polar (51.5 ± 3.5) diameters, ripening stage (mid-ripe and fully ripe), lack of decay and mechanical damage. They were washed in 0.2% detergent solution, treated with fungicide Prochloraz (49.5 g 100 L^-1 water) for 5 min and allowed to air dry.

Then the peaches were separated by the instrumental method of skin color in lots containing mid-ripe (hue angle 87.16 ± 3.06 °) and fully ripe (hue angle 78.41 ± 8.58 °) fruits. According to Cunha Júnior et al. (2007), peaches are considered mid-ripe when reaching values between 98 and 110 ° and fully ripe when reaching values between 90 and 110 °.

Peaches were packed in polystyrene trays (220 mm x 140 mm x 40 mm) and stored at three temperatures: 5.6 ± 1.57 °C and 72.8 ± 3.8% RH; 10.4 ± 0.5 °C and 95.8 ± 5.5% RH; and 21.04 ± 1.63 °C and 96.9 ± 2.6% RH for 28 days. During storage, fruits stored at 21.04 ± 1.63 °C were evaluated every two days and fruits stored at the other temperatures were evaluated every four days. The harvest day was assigned as day zero.

The experiment was conducted in a split plot arrangement, with the temperatures (three levels) in the main plots, the ripening stages in the subplots (two levels) and the evaluation days (eight levels) in the subsubplots, in a the completely randomized design with three replicates of five fruits per experimental unit.

Fruits were analyzed for CO₂ production by gas chromatography, using a Gow Mac Series 550P gas chromatograph equipped with a thermal conductivity detector and aluminium column filled with Porapak Q. The working conditions were: helium flow rate of 40 mL per minute, as the carrier gas, electric current of 150 mA, column, detector and injector temperatures were 50, 70 and 80 °C, respectively, and room temperature between 20 and 23 °C. The results were expressed in % or in mg of CO₂ kg^-1 h; fresh matter loss (gravimetric method), color of skin and pulp (digital colorimeter); pulp consistency (digital penetrometer probe of 12 mm), soluble solids expressed in ° Brix (digital refractometer), titratable acidity (TA) (titration with NaOH and the results expressed as % malic acid) according to the methodology described in AOAC ( 1997), vitamin C (titration reagent Tillman 2,6 dichlorophenolindophenol) according to the methodology described in AOAC (1997) and the results expressed in mg 100g^-1 of pulp, carotenoids (approximately 2.0 g ground in a mortar with washed sand, acetone 80% and a pinch of CaCO₃. The ketone extract was filtered through filter paper and the volume was completed to 25 mL. The absorbance was determined at 470, 646.8 and 663.2 nm and the levels of carotenoids calculated using the equations of Lichtenthaler (1987), in mg 100g^-1 of pulp.

Unfolding was used for data analysis, regardless of whether there was significant interaction or not, to demonstrate the behavior throughout the experimental period. Factor means were subjected to regression analysis. The models were chosen based on the significance of the regression coefficients, using the "t" test, the coefficient of determination (R²) and the potential to explain the biological phenomenon. The descriptive statistical analysis was used for CO₂ production.

RESULTS AND DISCUSSION

The respiratory peak of mid-ripe fruits stored at 5.6 °C occurred after 24 days (SD), with 18.7 mg of CO₂ kg^-1h^-1; for fruits stored at 10.4 °C, the peak occurred on day 20 SD (Figures 1A and 1B). Fruits stored at 21.04 °C reached the climacteric peak on day 6 SD, with mid-ripe and fully ripe fruits with 15.1 and 14.5 mg of CO₂ kg^-1h^-1, respectively (Figure 1C). Peaches cv. Douradão harvested at the commercial ripening stage and stored at 0 °C reached the peak on day 5 SD with 25 mg of CO₂ kg^-1h^-1 (Souza et al., 2009).

The loss of fresh matter had a linear decrease with days of storage (Figure 2). On day 8 SD, the mass loss was 15.2, 6.0 and 16.0% for mid-ripe fruits stored at 5.6 , 10.4 and 21.04 °C, respectively (Figures 2A , 2B and 2C) . Fruits stored at 10.4 ^oC had, at the end of storage (28 days), accumulated mass loss of 21.1 and 19.5% for mid-ripe and fully ripe stages, respectively (Figure 2B). Despite displaying more than 5% loss, the fruits showed no symptoms of shriveling, which would prevent its commercialization. Seibert et al. (2008) observed that peaches cv. Chimarrita after 10 and 30 days of refrigerated storage, when brought to 20 °C, showed slight wilting in the shoulder region. This symptom was a little more intense in peaches harvested at ripe stage. The mass losses were greater than 5% and led to shriveling, especially in peaches harvested at mid-ripe stage and after 20 days of storage. Shriveling was observed in ripe peaches cv. Chiripá after 20 days at 0 ºC. Mitchell (1992) reported 5% mass loss as a limit, before the peaches loose quality. For Crisosto et al. (2004), mass losses of 5% are normal for peaches and shriveling symptoms are noticed when they exceed 10%. For the cultivars Chimarrita and Chiripá, a loss limit of 5% and higher percentages can lead to symptoms of shriveling (Seibert et al., 2008).

Peaches harvest at the different ripening stage presented similar trend regarding skin and pulp color (Figures 3, 4, 5 and 6) and the temperature of 5.6 ^oC resulted in the smaller changes. The skin color of mid-ripe fruit stored at 10.4 °C had little change from the first day of evaluation (harvest day), which may allow extend the marketing period up to 28 days, without compromising the visual quality of the fruit. Mid-ripe fruit stored at 5.6 °C, had minor changes in skin color, however, there was impairment of fruit visual quality because of the high loss of fresh mass at the end of storage. A trend for color maintenance at low temperatures was also observed by Bron et al. (2002), who reported decreased levels of hue angle in fruits of cultivars Aurora 1 and Golden 2 with storage, as well as that fruit stored at lower temperatures resulted in less reduction of this variable compared with those stored at room temperature.

Fruits of all treatments showed a decrease of pulp consistency during storage, regardless of the temperature and the ripening stage (Figure 7). On day 8 SD, fruits stored at 21.04 °C showed consistency of 21.58 and 10.33 N for mid-ripe and fully ripe fruit stages, respectively, while for mid-ripe fruit stored 5.6 and 10.4 °C, consistency over the same period was 47.49 and 44.58 N, respectively, which demonstrates the potential of lower temperatures to conserve the fruit for longer periods. Cunha Júnior et al. (2010), studying the cold storage of peaches cv. Aurora 1 produced in Taiúva - SP, observed that ripe fruit stored at 12 °C had a sudden reduction in firmness, reaching 14 days SD with 7.9 N. Mid-ripe peaches had initial values of 46.5 N, 21.1 N in the same period. In this work, we observed that the ripe fruit stored at 10.4 °C had consistency of 25.37 N on day 16 SD, while mid-ripe fruits had consistency of 34.56 N. Peaches with low firmness have a lower transport resistance and, consequently, shorter shelf life (Toebe et al., 2011).

Both mid-ripe and fully ripe fruit reached at the end of storage SS contents of 16 and 21.1 °Brix, respectively (Figure 8). However, these levels of SS are due to the high fresh matter loss on day 28 SD, reaching 53.3 and 64.3% cumulative loss for mid-ripe and fully ripe fruit, respectively. At the other temperatures in this study, these levels were between 8.5 and 10.3 °Brix. Similar results were found by Cunha Júnior et al. (2010), who working with cv. Aurora 1, observed that mid-ripe fruits had lower SS (10.9 °Brix) than fully ripe fruits (11.6 °Brix).

The titratable acidity (TA) had a quadratic behavior along the days in all treatments (Figure 9). Ripe fruits showed lower TA when compared with mid-ripe fruits. According to Silva et al. (2010), the levels of organic acids, with few exceptions, tend to decrease with fruit ripening, due to the respiratory process or their conversion into sugars.

The vitamin C content decreased according the quadratic model throughout the storage (Figure 10). Ripe fruits showed lower ascorbic acid content when compared with mid-ripe fruits, and that the greatest losses occurred at 20.04 °C, when the ascorbic acid content of mid-ripe fruits decreased from 16.50 mg, on the harvest day, to 10.23 mg 100 g ^-1 on day 8 SD. In most fruits, the vitamin C content tends to decrease during the ripening process. Silva et al. (2012) attributes this decrease to the action of ascorbic acid oxidase (ascorbate oxidase). The activity of this enzyme is larger in ripe fruits than in unripe fruits, which may explain the losses during the fully ripe stage. Segantini et al. (2012), characterizing the pulp of different peach cultivars, found ascorbic acid content of 16.02 mg 100 g^-1 for fully ripe fruit of cv. Aurora 1.

The content of carotenoids was higher in ripe fruits and there was increase in their amounts in all treatments (Figure 11). The content of carotenoids increases during fruit ripening and color intensification is due to the loss of chlorophyll ( Melendez-Martinez, 2004). The content of total carotenoids increased during the ripening of many fruits, when carotenogenesis is enhanced (Lima et al., 2002), as in mango (Silva et al., 2012).

CONCLUSION

For the characteristics evaluated in this study, the best efficiency in maintaining postharvest quality of peaches cv. Aurora 1, cultivated in the Zona da Mata region, Minas Gerais, was obtained with fruits harvested at the mid-ripe stage and kept at the temperature of 10.4 °C.

ACKONOWLEDGEMENTS

The authors thank CAPES, CNPq and FAPEMIG for the financial support.

Received: 20/09/2012

Accepted: 26/06/2013.

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1

Research developed with financial support from CAPES, CNPq and FAPEMIG.

Publication Dates

• Publication in this collection
  17 Feb 2014
• Date of issue
  Dec 2013

History

• Received
  20 Sept 2012
• Accepted
  26 June 2013