Agriculture Extension الإرشاد الزراعي

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Browsing Agriculture Extension الإرشاد الزراعي by Author "Hiba Ahmad Mahmood Abed"

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    Influence of Transglutaminase and Thermal Treatment on Yield and Storage Stability of Traditional Palestinian Dairy Products
    (Al-Quds University, 2023-08-07) Hiba Ahmad Mahmood Abed; هبة أحمد محمود عابد
    In the conventional dairy processes, a considerable amount of protein is lost with the whey, as protein is a valuable component of milk and milk products, therefore, incorporating whey proteins in dairy products will increase the yield, as the presence of whey proteins allowed higher moisture retention, due to their hydrophilic property, and thus higher yield obtained.Several methods have been used to reduce the whey separation in dairy products, such as application of stabilizers, milk derived constituents, and starter cultures. One of the methods that also used to reduce loss of whey protein is the enzymatic treatment of milk with Transglutaminase. TG enzyme form new intra- and intermolecular crosslinks between milk proteins. Such crosslinks can modify the structure and functionality of the proteins. Several factors affect the efficiency of Transglutaminase whey proteins crosslinking with curd proteins. One of the most important factors is heat treatment of milk. Thus, this study aimed to investigate the influence of different pasteurization temperatures combined with different enzyme concentrations, on the yield and whey percentages in the concentrated yogurt (Labneh), and in the yield percentage of the local white- brined cheese. Concentrated yogurt (Labneh) milk was pasteurized at different pasteurization temperatures (65 C°/ 30 min, 72 C°/ 15 sec, 82 C°/ 15 sec, and 90 C°/ 15 sec), and after each pasteurization, the milk was treated with different TG ratios (0, 1, 3, and 5 gm TG/kg milk). As well as, in the local white- brined cheese manufacturing, milk was pasteurized at different pasteurization temperatures (65 C°/ 30 min, 72 C°/ 15 sec, and 82 C°/ 15 sec), and after each pasteurization, the milk was treated with different TG ratios (0, 1, 3, and 5 gm TG/kg milk).This study demonstrated that the inclusion of TG into the concentrated yogurt increases yield percentage, and reduces whey loss. In addition, TG inclusion into the local white brined cheese increases the yield percentage. The obtained yield improvement was due to TG crosslinking of milk proteins. Results showed that the concentrated yogurt yield significantly improved when the milk was pasteurized at (90 C°/ 15 sec), followed by treatment with enzyme ratio of (3 gm TG/ kg milk). For the local white- brined cheese, yield significantly improved when the milk was pasteurized at (72 C°/ 15 sec), and followed by treatment with enzyme ratio of (3 gm TG/ kg milk).Concentrated yogurt (Labneh) samples with highest yield and lowest whey percentages, as well as, the local white brined cheese samples with highest yield percentage, underwent physicochemical and microbial analysis when fresh, at (15, and 30) day of storage period. The physicochemical results for both products showed that samples produced with enzyme treatment exhibited higher pH values, lower titratable acidity values, higher moisture content, lower syneresis (for treated Labneh samples), and lower dry matter content (for treated cheese samples). In terms of microbial analysis, results showed that in treated Labneh samples enzyme crosslinking retard the growth of lactic acid bacteria resulting in lower numbers and longer time of coagulation. In treated local white- brined cheese samples, coliform counts were lower than the control during storage period. However, both TG treated products exhibited higher yeast and mold growth than the control samples.The study recommended mainly to use TG as method to improve the yield, especially if combined with the suitable pasteurization temperature for each product. In addition to the possibility of dispensing the stabilizers use. It also recommends further studies to investigate the sensorial and rheological properties of TG treated samples. As well, studies needed to investigate the effect of transglutaminase addition on the fermentation or coagulation time; to take time cost into consideration.