The aim of this study was to improve the rheological, physical and organoleptic properties of non-fat yogurt using microbial Transglutaminase (MTGase), Exopolysaccharides producing culture (EPS) and two commercial stabilizers based on pectin and gelatin. Results showed that non-fat yogurt samples produced by textural impotents haven't significant differences with control full-fat yogurt sample in moisture content at fresh, while there were significant differences between these samples and control non-fat yogurt sample. Moisture content significantly decreased in all yogurt samples except in control full and non-fat yogurt samples after 10 days of storage period. Non-fat yogurt EPS sample had the highest percentage moisture content compared with control (full-fat and non-fat) yogurt samples and experimental non-fat yogurt (MTGase, commercial pectin and gelatin) samples throughout storage. Pro/D.M was higher in control non-fat yogurt, non-fat yogurt EPS and non-fat yogurt produced by commercial gelatin compared with non-fat yogurt (MTGase, commercial pectin) and full-fat yogurt samples at fresh. There were no significant differences in Fat /D.M % between non-fat yogurt C2 and non-fat samples containing textural improvements, while there were significant differences between them and control full-fat yogurt C1 at fresh or during storage period. There were no significant differences in acidity among all treatments. Hardness was significantly lower in the EPS non-fat yogurt compared with the other treatments throughout storage period. The non-fat yogurt containing EPS producing culture and non-fat yogurt containing commercial stabilizers had a lower level springiness, Chewiness and gumminess than the full-fat yogurt sample and non-fat yogurt containing MTGase. Adhesiveness significantly increased during storage period for all treatments. There were no significant differences in syneresis percentage among all treatments. Non-fat yogurt produced by Exopolysaccharides producing culture, microbial Transglutaminase and commerial gelatindemonstrated rheological and physical properties were closer to that of control full-fat yogurt.

Calf rennet has been used in Domiati cheese making for long times. Calf rennet is traditionally obtained from slaughtered calves. However, due to shortage of meat, calves were recommended to be fattened for two years. This cause a sharp decrease of calf rennet available. Researches have been trying to evaluate the applicability of calf rennet substitutes. These substitutes are : adult bovine rennet (ABR), microbial rennet from Mucor miehei (MR) and mixtures of calf rennet and adult bovine rennet at different ratio .This study was intended to evaluate different close of rennet as alternative to Calf rennet in coagulant milk and factors affecting the enzymes activity.Results showed that milk clotting time was positive correlated with sodium chloride concentration. But milk clotting time was inversely correlated with calcium chloride concentration and temperature. Milk clotting time was decreased as milk solids increased up to 12% under all treatments.

Ras cheese is the main Egyptian hard cheese that is well-known worldwide. Herein, we investigated how different salting techniques affect the physio-chemical properties, sensory properties, and volatile compounds of Ras cheese over a six-month ripening period. Five Ras cheese treatments were made from pasteurized cow’s milk using various salting techniques: traditional salting of Ras cheese, salting by applying all of the salt to the curd after the entire whey drainage, salting by applying all of the salt to the curd after half to two-thirds of the whey drainage, salting in a brine solution for 24 h without dry salting, and salting in a brine solution for 12 h and then dry salting. The obtained results by GC-MS recorded that thirty-eight volatile compounds were identified in Ras cheese treatments after six months of ripening, and the development of volatile compounds was affected by the salting technique as well as the ripening period of the cheeses, which played a major role in the type and concentration of volatile compounds. Results revealed that there are six esters, 15 fatty acids, five ketones, two aldehydes, four alcohols, and eight other compounds identified in most treatments. Some physio-chemical characteristics and sensory properties were found to have high correlations with the storage period, while some others have low correlations during the ripening period.

Ras cheese is one of the main hard cheeses in Egypt and is well-known worldwide. Herein, we investigated the potential effects of different coating techniques on the physico-chemical characteristics, sensory properties, and aroma-related volatile organic compounds (VOCs) of Ras cheese over a six-month ripening period. Four coating techniques were tested, including (I) uncoated Ras cheese (the benchmark control), (II) Ras cheese coated with paraffin wax (T1), (III) Ras cheese coated with a plastic film under a vacuum (PFUV; T2), and (IV) Ras cheese coated with a plastic film treated with natamycin (T3). Although none of the treatments significantly affected the salt content, Ras cheese coated with a plastic film treated with natamycin (T3) slightly reduced the moisture content over the ripening period. Moreover, our findings revealed that while T3 had the highest ash content, it showed the same positive correlation profiles of fat content, total nitrogen, and acidity % as the control cheese sample, indicating no significant effect on the physico-chemical characteristics of the coated cheese. Furthermore, there were significant differences in the composition of VOCs among all tested treatments. The control cheese sample had the lowest percentage of other VOCs. T1 cheese, coated with paraffin wax, had the highest percentage of other volatile compounds. T2 and T3 were quite similar in their VOC profiles. According to our GC-MS findings, thirty-five VOCs were identified in Ras cheese treatments after six months of ripening, including twenty-three fatty acids, six esters, three alcohols, and three other compounds identified in most treatments. T2 cheese had the highest fatty acid % and T3 cheese had the highest ester %. The development of volatile compounds was affected by the coating material and the ripening period of the cheeses, which played a major role in the quantity and quality of volatile compounds.

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