الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Fruits are rich with antioxidants that help in lowering incidence of degenerative diseases such as cancer, arthritis, arteriosclerosis, heart disease, inflammation, brain dysfunction and acceleration of the ageing process. The freezing and drying preservation of fruits is one of the growing food industries in Egypt in the last decade. We selected Egyptian apple and banana to use experimental in this research. We used some treatments such as:
1. Thermal treatments:
*Blanching on degree 100°C (1, 2 and 5 min.)
*Steaming on degree 100°C (1, 2 and 5 min.)
2. Chemical treatments
*Ascorbic acid (0.5, 1 and 2%)
*Citric acid (0.5, 1 and 2%)
*Sodium metabisulfite (Na2S2O5) (0.05, 0.1 and 0.2%)
3. Natural extract treatments:
*White cabbage extract(5, 10, 15, 20 and 25%)
*Taro pulp extract (5, 10, 15, 20 and 25%)
*Taro peel extract (5, 10, 15, 20 and 25%)
The optimum temperature for activity of banana and apple of PPO, POD and CAT enzyme activity was 40°C. The enzyme activity decreased with increasing temperature and time showing less activity at 70°C. The maximum activity was 0.2 M catechol,0-phynelenediamine and sodium perborate with increasing the concentration a corresponding decline in activity was noticed. The results mentioned above concerning the effect of pH, temperature and substrate concentration derived from the study of crud enzyme combination of isoenzymes and interaction with nonenzymatic proteins. High degree of inactivation has been achieved in the first 2 min until 5min of water and steam blanching treatment. The best concentration of ascorbic acid was 2.0% to effect in improving it final acceptability and to make inhibition of PPO activity in various fruit slices, especially for banana and apple. Also, the best concentration of CA 2.0% or inhibition of PPO in banana and apple. However, it could be noticed that addition of Na2S2O5at 0.2% in the soaking solution took place as the inhibition of PPO increased.
Generally, the result showed that the CA, Na2S2O5 and steam blanching heated samples were not found any browning after 8weeks storage at -18°C for all banana pulp compared with AA, water blanching and untreated samples. The apple slices pretreated with Na2S2O5, steam and water have also the highest reduction of Yeast & Molds and bacteria followed by CA, 1)ut it pretreated with AA and untreated samples were the lowest reduction of yeast & molds and bacteria after 4 months stored at 25°C. The low pH of apple products restricts the growth of a wide variety of microorganisms. Only yeast, molds and lactic acid bacteria are capable of prolific growth in apple products. Significant organisms present in processed apple products fall into three categories-spoilage organisms, pathogenic organisms and fermentation organisms. Growth of yeast, mold and bacteriamay lead to production of off-flavors and unacceptable filamentous structures in processed apple products. The percent of inhibition (%) of PPO, POD and CAT was high in 15% of taro pulp and peel treated apple slices (78.60-77.77%) versus 76.95% in 15% in cabbage treated slices. Which means that the taro extracts treated slices was higher than the cabbage extract treated slices and untreated apple slices.