Preparation low-energy yogurt fortified with pectin extracted from eggplant peels and calyxes and studying its storage capacity

Abstract

The current study aimed to add pectin extracted from the peels and calyxes of eggplant in the manufacture of low-energy yogurt with different proportions (0.1, 0.3, 0.5) g pectin/100 ml skimmed milk, in addition to the control treatment without any addition to milk and study its effect on the chemical, physical and microbiological properties for yogurt. The value of pH and the titration acidity of the skimmed yogurt manufactured by adding the extracted pectin indicated that there were no significant differences between the control treatment (T_C) and the treatments which the extracted pectin was added immediately after the manufacturing process, while it was noted that there was a significant decrease in the pH values ​​with an increase in the acidity values with increase in the cold storage and for all treatments. That addition of pectin extracted from eggplant peels and calyxes to skimmed milk improved the physical characteristics of yogurt, including viscosity, whey exudation and water holding capacity during refrigerated storage periods of 21 days compared to the control treatment (T_C). The total numbers of bacteria varied for the yogurt treatments with added pectin extracted from eggplant peels and calyxes, as the increase in the total numbers of bacteria decreased with increasing the storage period compared to the control treatment (TC) which increased the total numbers of bacteria with increasing the storage period. The results of the numbers of psychrophilic bacteria, yeasts and molds showed that all treatments were free of them in the first and second week of storage, and numbers began to appear in the third week of storage for the control treatment and treatment (T1) by adding (0.1) g pectin / 100 ml milk, while the numbers did not appear in the rest of the treatments ( T2, T3) only on the last day of storage.The results also showed that all yogurt treatments were free of coliform bacteria, starting from the day of manufacture until the end of the 21-day storage period.