The Research Of The Banana Quality Change Rules And Control During Refrigeration And Storage

Banana is a kind of fruits, with short production cycle, high economic benefit, high nutritional and medicinal value, active breathing and uneasy to be stored. Given this,bananas were used in this research as experiment material to study bananas quality change rules and control the change in the process of freezing and storage. Several research aspects are included in this paper:1. Bananas colorprotection research before frozenFirstly, from the aspect of the chemical color-protection research, based on the results of single factor experiments and the index of bananas brown stain inhibition rate before frozen, the orthogonal experiments with six factors at two levels were processed;then we used the range analysis to select four single color fixatives(L-cysteine, phytic acid, D-ascorbic acid sodium, EDTA-2Na) that have great impact on the brown stain inhibition, and utilized the Design-Expert 8.0 for response surface analysis. Results showed that the optimal color fixative formula of quick-frozen bananas was as follows:the concentration of L-cysteine is 0.14%, phytic acid concentration 1.32%, EDTA-2Na concentration 1.28%, and D-ascorbic acid sodium concentration is 1.70%. At this moment, the brown stain inhibition rate was predicted to be 60.10%, 98.25% close to the actual value of 61.17%. The actual quantity of different additives in the bananas after the color-protection treatment according to the optimal compound color fixative formula was determined to meet the national standards.Secondly, in terms of physical color-protection research, we summarized the influences of the blanching temperature, blanching time, ratio of blanching liquid to material and the cooling temperature after blanching treatment on the treated banana color, texture, PPO and POD enzyme activity; determined the cooling temperature after blanching treatment at- 5℃. Then we selected the blanching temperature, heat time and ratio of blanching liquid to material as three factors, PPO enzymatic activity in blanching-treated bananas as an index; adopted the response surface method to establish the polynomial mathematical regression model for blanching pretreatment conditions of the frozen bananas, and determined the best blanching pretreatment conditions:blanching temperature is 100℃, blanching time is 2.0 min, the ratio of blanching liquid to material is 20:1, the enzyme activity of the blanching-treated bananas is 20.097 U/gunder such condition and treatment. The banana under such treatment was also tested by the physical and chemical indicators.2. Bananas quality change rules and quick-frozen temperature determination in the frozen processEither pretreated by the compound color fixative or by the blanching process, the banana’s slow frozen temperature was between-15 ℃ and-55 ℃ and quick-frozen temperature was-70℃(the time to pass the maximum ice crystals producing area is1520 s at frozen temperature of-70℃ after the compound color fixative pretreatment; the time to pass the maximum ice crystals producing area is 1500 s at frozen temperature of-70℃ after the blanching pretreatment.). The super-cooling point temperature range of the frozen bananas after the compound color fixative treatment is between-2.7℃ and-3.4 ℃; the freezing point temperature range is between-2.6 ℃ and-3.1 ℃. The super-cooling point temperature range of the frozen bananas after the blanching treatment is between-1.9℃ and-3.1℃; the freezing point temperature range is between-2.1℃ and-2.9℃. As the frozen temperature decreased, the reducing sugar content in banana, pH value, soluble solids content, juice wastage rate and conductivity decreased gradually; the L value of colour and luster and the moisture content basically remained unchanged; the better the integrity of the freeze banana cells was, so was the bananas frozen at temperature of-70℃ after color protection treatment. We determined that the best frozen temperature is at-70℃for frozen bananas.3. Bananas quality change rules and quick-frozen conditions determination in the frozen processFrom the overall, with the increase of storage time, the pH value of frozen bananas decreased slightly; soluble solids content increased slightly;the law of the reducing sugar content rose slightly; the color L-value declined and then gradually leveled off; the wastage rate of the drying loss and juice and conductivity rate increased gradually. From overall, the lower the banana storage temperature was, the more slightly each index range changed, indicating that the low storage temperature is helpful to maintain the quality of the banana. With the increase of storage time, the sensory score of the frozen bananas was gradually reduced; the lower the storage temperature was, more slightly the sensory score of the frozen bananas changed. Whether the bananas frozen after blanching treatment or color-protection, its sensory score is the highest at the storage temperature of-28 ℃. So, we determined that the best storage temperature is at-28 ℃ for frozen bananas. Storage temperature for-8℃, the banana that pretreated by the compound color fixative can be stored less than 20 d, pretreated by the blanching process can be storedfor at least 60 d;The storage temperature between-18℃ to-28℃,either pretreated by the compound color fixative or by the blanching process, the bananas can be stored for at least 60 d.4. New bananas products developmentChocolate banana cracking ice cream process optimization: in combination with single factor experiments to determine the effect of the best single color fixative(ascorbic acid, L-cysteine, citric acid), color-protection time(20min), heat temperature(100℃) and heat time(1.5 min) benefiting the banana core enzyme deactivation, banana core frozen temperature(-70℃), the best chocolate coated temperature(50℃). The best color fixative recipe of the chocolate banana cracking ice cream was determined by the orthogonal experiment and sensory score is that: L-cysteine addictive proportion is0.10%, citric acid 0.35% and ascorbic acid 0.20%; the best time for color protecting is for 20 min, best blanching time under 100 ℃ is for 2.0 min, the best temperature of chocolate coating is 55℃. The physical and chemical indicators and health indicators were in line with national standards.Banana ice cream study: according to the single factor, the best heat time of mixture mashing was 9 min; according to the single facto study in the banana ice cream formula,we determined the best proportion range of banana and milk powder(8:1~14:1) and that of banana and milk(4:1~8:1), the best addictive level of citric acid(0.05%~0.15%).On this basis that the comprehensive score of banana ice cream was the response value,the response surface method was used to analyze the banana ice cream recipe, to establish the polynomial regression model, to get the best banana ice cream formula: the ratio of banana and milk powder is 11.22:1, the ratio of banana and milk is 5.46:1, and the citric acid concentration is 0.09%. At this moment, the forecasted comprehensive score of the banana ice cream can reach 93.76 points, in 99.74% conformity with the actual value of 94.00 points verified. The physical and chemical indicators and health indicators were in line with national standards.