Characterization and study of functional properties of banana starch green variety of Mysore ( Musa AAB-Mysore )

The market starches, resistant, native and modified rapidly growing and products from starchy have been continuously developed. Consequently, its features are widely studied to meet specific technological properties (Jambrak et al., 2010). Besides the interest of ingredients containing components that influence in physiological or metabolic beneficial activities, the food industry search starches with features that provide increase your range of options in the processing of certain foods.


Introduction
The banana belongs to the genus Musa of Musaceae family and the most important varieties grown in Brazil are: Silver, Pacovan, Dwarfed Silver, Apple, Mysore, Land and D' Angola, belonging to the group AAB genome; and Nanica, Nanicão and Grande Naine, belonging to the genome group AAA (Mota et al., 2000).
Fundamental characteristics of quality for consumers as flavor, aroma and texture (Matsuura et al., 2004) they are not always favorable in all varieties, so it should be considered processing options after the improvement of fruits for their increased use in the food industry.
The market starches, resistant, native and modified rapidly growing and products from starchy have been continuously developed.Consequently, its features are widely studied to meet specific technological properties (Jambrak et al., 2010).Besides the interest of ingredients containing components that influence in physiological or metabolic beneficial activities, the food industry search starches with features that provide increase your range of options in the processing of certain foods.
Given the importance of the banana crop in our country and taking into account the possibility of a nonconventional source of starch, the objective of this study was to characterize the green banana variety, Mysore (Musa AAB -Mysore), used as a raw material for the extraction of starch.And, out of this native starch, to perform the characterization and study of the functional properties.

Physical characterization of banana
The firmness of the bananas was evaluated by penetrometer (Instrutherm Measuring Instruments Ltda. , Brazil).

Extraction and purification of starch
The extraction of starch was carried out according to the methodology described by Adebowale et al. (2006) with adaptations: 3.3 kg of bananas cut into slices were soaked in at full speed for 8 sec.The obtained suspension was sieved mesh 200 meshes and allowed to stand for 24 h at 4 °C.The obtained starch was washed twice with distilled water before drying in an stove with forced air circulation for 3 h at 45 °C ± 2 °C.It was then stored in polyethylene bags until further use.

Chemical composition
The banana and starch were characterized by the moisture content infrared balance, protein by Kjeldahl distiller and ash through the muffle according to the methods 44-15.02, 46-12.01 and 08-01.01 (American Association Cereal Chemists, 2010).The titratable acidity and pH were determined by pH meter according to the methods 981.12 and 942.15 (Association of Dfficial Analytical Chemists, 2005).
The content of reducing carbohydrates is performed by DNS method proposed by Miller (1959).Quantification of the starch was carried out according to the method of anthrone (Moraes & Chaves, 1988) and the determination of phenolic compounds was performed according to procedures Goldstein & Swain (1963) based on tannin content present in the banana.The apparent amylose content of the starches was previously degreased was determined according to the methodology described by Martínez et al. (1989).

Morphology of the starch granules
The Scanning Electron Microscopy (SEM) was performed with energy dispersive x-ray detector Leo 440i (LED Electron Microscopy Ltd.  , Cambridge United Kingdom).Before the analysis, the samples were placed on stubs and coated with gold in a sputter coater model SC7620 (VG Microtech, Uckfield, UK).A treatment of images was performed for the approximate determination of the size of the particles using the software ImageJ.

Thermal starch property
The Differential Scanning Calorimetry (DSC -Differential Scanning Calorimetry) was used to evaluate the thermal properties of starches although the DSC-60 calorimeter (Shimadzu, Japan) calibrated with indium.The transitions were characterized by the initial temperature (T 0 ), peak (T p ) and end (T e ), and the change in the enthalpy (∆H) associated with the gelatinization process of the starch.These parameters were calculated using the TA60 software version 2.11 (Shimadzu, Japan).Two replicates were performed for each sample (proportion starch: water 1: 2).

Degree of molecular organization of starch
The degree of molecular organization was examined by infrared spectroscopy Fourier Transform (FT-IR).Infrared spectra (4000 to 400 cm -1 ) of the samples (pellet formed by 2 mg of the starch and 200 mg of KBr) were obtained in Fourier transformed spectrophotometer (FT-IR) IR Prestige-21 (Shimadzu, Japan).Measurements were taken at a resolution of 4 cm -1 with 45 scans scan.It was used the IR Solution software version 1.21 (Shimadzu, Japan) to analysis of the curves fit.

Gelation study
The study of capacity of the starch gelation was analyzed according to the method described by Lawal & Adebowale (2005), in which starch suspensions at different concentrations were heated and cooled to obtain the minimum gelation concentration.

Paste properties
The starch paste properties were determined in the viscometer RVA (Rapid Visco Analyzer) Model 4+ (Newport Scientific Pty. Ltd.  , Australia) using the standard heating program 1.The viscosity profile and the parameters were calculated using the Thermocline software for Windows version 2.4 (Newport Scientific Pty. Ltd., Sydney, Australia).The measurements were performed in triplicate.

Syneresis
The syneresis was measured as the percentage (%) of water mass released over the initial weight of the starch, after centrifuging the samples at 1500 g for 15 minutes (Singh et al., 2004).

Swelling and solubility of starch
The methodology used for quantifying the swelling power and solubility of starch in function of the temperature is described as De La Torre-Gutiérrez et al. ( 2008), and then in function of pH were used the procedures described by Lawal & Adebowale (2005).

Absorption capacity of water and oil
Water absorption capacity (% WAC) and oil (DAC%) of green banana starch was performed by the method proposed by Beuchat (1977), using centrifugal Cientec  CT-5000R at 2000 rpm for 15 minutes at room temperature.

Clarity folder
The clarity of the paste was determined using the Singh et al. (2004) method with some modifications, with reading performed in spectrophotometer Biospectro  SP-220-650 nm transmittance at 24, 48, 72 and 120 h time.

Statistical analysis
The results were analyzed by analysis of variance (ANDVA) and submitted to the mean comparison test by Tukey, at a significance level of 5%, using Assistat program (Silva & Azevedo, 2009).Moreover, the data obtained in the study of some properties were expressed in graphs form in Figure 1, prepared by Excel software.

Results and discussion
The bananas had 28.72 N of firmness; it is the best parameter to determine the degree of ripeness of the fruit according Ditchfield (2004).The yield of extracted starch was 13.57%.The various techniques and existing varieties of banana, as well as various forms of extraction used in obtaining que starches are not a pattern exists in relation to the yield of this type of starch.

Chemical composition
In the Table 1 shows the results of the characterization of Mysore banana and starch extracted from the same.The moisture content presented results already expected, considering the banana in maturation stage must contain certain water content (60.07%) and after the extraction procedure, the starch has a high reduction of this content is falling percentage of 30.12%.The ash and protein content of the banana was 1.37% and 0.72%, respectively.Low ash and protein content indicate a higher quality of extracted starch as well as the procedure used in order that after extraction, the starch carries some constituents present in the tissues, even though in low amounts, may interfere with their properties (Leonel & Cereda, 2002).The values of acidity and pH of banana and starch were within expectations.The content of reducing sugars of the banana (0.36%) was within the range 0.10 to 0.90% (Leonel et al., 2011;Carvalho et al., 2011), value conducive to a still green fruit.
The amylose content of the starch was of 37.88%, which can influence effects such as starch granule swelling, gelatinization, and downgrading behavior during ingestion.The content of phenolic compounds found in banana and in the starch were low, being favorable for checking the undesirable features to food because it is an anti-nutritional factor (Pino & Lajolo, 2003).

Morphology of the starch granules
The Figure 2 shows the particles through image captured by scanning electron microscope (SEM), showing beads with sizes and different shapes, wherein there is a predominance of the ellipsoidal shape with irregular diameters ranging between axes 10 and 100 micrometers and smooth surface, which, according to Barbosa (2013), demonstrates integrity granules.Utrilla-Coello et al. (2014) studying Enano starch of banana, Morado, Valery and Male found that the major axes obtained similar variation to the Mysore starch, between 10 and 80 micrometers.The particle size amounted area and perimeter averages of 277.67 μm2 and 141.33 micrometers respectively (Figure 2).It was counted about 53 particles.

Thermal starch property
The curve Differential Scanning Calorimetry (DSC) is set in the Figure 3.The initial temperature (T 0 ), peak temperature (T p ) and end temperature (T e ) of the endotherm peak of gelatinization was 67.54 °C, 75.18 °C and 87.56 °C, respectively.
The enthalpy founded was 12.38 J/g.The gelatinization time is represented by T e -T 0 temperature range, which was 20.02 °C.Note, according to the obtained results (Figure 3), that only an endothermic peak was obtained during the analysis of starch, which suggests, according Yoo & Jane (2002), that no amylose complexed with lipids.Similar results of the temperature and enthalpy were found in varieties like Nanicão Silver Anã, Morado and Male (Leonel et al., 2011;Utrilla-Coello et al., 2014).These results may be closely associated with the amylose levels found that ranged from 19-37%.

Degree of molecular organization of starch
The infrared spectrometry by Fourier Transform (FT-IR) has been used to estimate the amount of crystalline and amorphous domain of the starch structure, for evaluating the intensity of the absorbance at 1047 and 1022 cm -1 , respectively (Capron et al., 2007).
To make the rate of absorbance of the spectrum between the bands 1047 and 1022 cm-1 with the Mysore banana starch (Musa AAB -Mysore) find the value 0.92, that indicates a predominance of crystalline order of the molecules in the pellet.This predominance of crystalline area below the amorphous area of the bead is much higher compared to the proportion found in green banana starch granules from other species as Williams and Red Banana of China (Musa coccinea), whose rates of these absorbance were close to 0.60 and 0.55, respectively (Jiang et al., 2015).

Gelation study
The Figure 4 clearly shows the results obtained in the study of gelation capacity of the Mysore banana starch.There was a variation according to the change in concentration of the samples.
At a concentration of 2%, the starch presented liquid estate and in the 4%, notorious viscosity.With 6%, the viscosity has become firmer.Already at a concentration of 8% the starch shows a gelling state formation, which determines this percentage as the minimum concentration of gelation, because the sample of the inverted tube did not reach to slide in it (Figure 4b).
In the concentration range from 10 to 14% the starch proved to be completely steady, surpassing the gel point.Results of the minimum concentration of the gelation between 6 and 10% can be found in several studies with the starches extracted from unconventional sources (Farias et al., 2013;Cavalcanti et al., 2011).

Paste properties
The results obtained by Rapid Visco Analyser (RVA) in the starch can be seen on Table 2.The breakdown viscosity (breakdown) got higher result when compared to other native starches studied by Ascheri et al. (2010), Leonel et al. (2011), Dliveira et al. (2009) e Mota et al. (2000), indicating less resistance of gelatinized granules to mechanical fragmentation under shear.
It's perceptible a marked loss of the viscosity during the heating and shear process (Figure 5).At setback value it is observed that the banana starch has fewer tendencies to downgrading compared to other starches (Leonel et al., 2011;Ascheri et al., 2010).The paste temperature obtained by RVA was 79.1 °C, value that shows the approximate temperature range found by Leonel et al. (2011), which was 60-73 °C in banana starches.This value is consistent with the peak temperature shown in the DSC (75.18 °C) and shows a high resistance to expansion and rupture.

Syneresis
It was observed that the starch gel showed syneresis after 24 hours of refrigerated storage and that syneresis increased to 48 hours.However, after 48 h, the syneresis percentage was decreasing, ranging from 10.51% ± 0.51 to 2.80 ± 0.54% (360 h), amounting to a loss of water of total 33.46%.
Low results of syneresis after a certain storage time, according to Muccillo (2009), may indicate that the starch is less prone to downgrading.This characteristic is enhanced where there is the result of the setback obtained in the RVA analysis.Low water contents released by starch gel as obtained in this study (33.46%) may indicate a higher possibility of applying starch or other refrigerated products which is undesirable syneresis (sauces, etc.).

Swelling and solubility
As there was a temperature rise from 70 °C, there was an increase in the swelling of starch granules (Figure 1a).The swelling continued gradually to 90 °C, which is consistent with the results found in the DSC analysis.951.0 ± 66.9 Triplicate average ± standard deviation.
An exponential increase in swelling can be noticed between 70-80 °C temperature range that is associated with the DSC peak temperature (75.18 °C) and of the paste of the RVA (79.1 °C).
Regardless to solubility, it was observed that there was an increase this property or swelling of the granules (60-70 °C) (Figure 1b).However, after 70 °C there was a reduction of solubility, probably due to disruption of the granule structure and leaching of compounds in the granules.
According to Sajilata et al. (2006), starches with reduced in the solubility can be directed to certain industrial applications, it offers good crispness and low water retention and fat.
The variation of the pH between 3 and 9 caused little effect on the solubility and swelling power of the starch (Figure 1c).However, from pH 9, there was an increase in these properties until pH 12.This was probably due to deprotonation of the hydroxyl groups of the starch molecules, leading to expulsion thereof and allowing greater water penetration in the granule (increased swelling and solubility).

Absorption capacity of the water and oil
In the water absorption capacity (WAC), a starch obtained a value of absorption of 1.19 g water / g starch.In the oil absorption capacity (DAC) gave a similar value when compared to water, 1.18 g oil / g starch.According to Resio et al. (2000), these characteristics can define the industrial interest of the starches in the formulation of food products.

Clarity folder
The higher the transmittance the higher the light of the folder, which indicates lower opacity and absorbance values.With the passage of the storage time the starch gels exhibited a decrease in transmittance and, consequently, greater opacity.Visually, starch gels can be considered moderately transparent compared to starch gels obtained by Silva et al. (2006), what makes their utilization is intermediary between the application in salad dressings or toppings of sweet pies, for example.

Conclusions
Mysore banana starch yield was low; however, this starch showed good features physicochemical and functional properties.It showed good power of swelling, which shows the potential for its use in products that require water retention, such as meat products and jellies.
The low percentage of water loss during storage and low setback obtained by folder profile study show that the starch is less prone to downgrading and syneresis, quite considerable

Figure 1 .
Figure 1.Swelling power (a) and solubility (b) in function of the temperature of the Mysore banana starch.Swelling power (c) and solubility (d) in function of the pH of the Mysore banana starch.

Figure 2 .
Figure 2. Morphology of the starch granules by SEM.

Figure 3 .
Figure 3. DSC curve for the banana starch.

Figure 4 .
Figure 4.The starch samples with different concentrations (a); Minimum concentration of gelling obtained (b).

Figure 5 .
Figure 5. Viscosity profile of paste of Mysore banana starch.

Table 1 .
Physical-chemical assessment of the green banana and the extracted starch.

Table 2 .
Property of the paste (VAR) of Mysore banana starch.