Pasteurization failures in the dairy industry have been reported in many previous studies. Hence, ultrasound, as a nonthermal alternative to pasteurization, has been studied in recent years. In this research, retentate of ultrafiltered milk was pasteurized, inoculated with Escherichia coli O157:H7, Staphylococcus aureus, Penicillium chrysogenum, or Clostridium sporogenes, and then treated with ultrasound for 20 min at frequencies of 20, 40, and 60 kHz and intensity of 80%. Microbial and physicochemical properties of the subsequently produced ultrafiltered white cheeses were investigated throughout 60 d of ripening. Sonication at 20, 40, and 60 kHz reduced counts of E. coli O157:H7, S. aureus, P. chrysogenum, and Cl. sporogenes by 4.08, 4.17, and 4.28 log; 1.10, 1.03, and 1.95 log; 1.11, 1.07, and 1.11 log; and 2.11, 2.03, and 2.17 log, respectively. Sonication improved the acidity of ripened cheese, and sonicated samples had lower pH values than control samples at the end of storage. Sonication did not affect fat in dry matter or the protein content of cheese during ripening, but it did accelerate lipolysis and proteolysis; the highest rates of lipolysis index (free fatty acid content) and proteolysis index (water-soluble nitrogen) were observed on d 60 of ripening for samples sonicated at 60 kHz. Sonication did not affect cohesiveness or springiness of cheese samples, but hardness and gumminess increased in the first 30 d and then decreased until 60 d of storage. Furthermore, ultrasound treatment improved organoleptic properties of the cheese. In terms of overall acceptance, samples sonicated at 60 kHz received the highest sensorial scores. Results showed that sonication can improve microbial, physicochemical, and sensorial properties of ultrafiltered white cheese.
The effect of interesterification on oxidative stability of cottonseed, palm and soybean oils stored under oven conditions at 45, 60 and 75C was evaluated by measuring the peroxide values (PV), anisidine values (AV) and Totox values at different time intervals. Fatty acid composition and tocopherol contents of oil samples were determined before and after interesterification. Interesterification reduced the tocopherol content of oils. The interesterified oils showed lower PV and AV than their non‐interesterified counterparts in all temperatures and time intervals. The primary and secondary oxidation reaction constants and reaction orders were investigated as a function of the reaction temperature. The interesterified oils showed lower reaction rate constants than the non‐interesterified samples. Based on PV, AV and reaction rate constants, the oxidative stability of interesterified oils were higher than their non‐interesterified counterparts. PRACTICAL APPLICATIONS The actual shelf‐life of oils can be evaluated by following the deterioration process as a function of time and temperature. Kinetic models were predicted for further estimation of oxidation rate of natural and interesterified oils. It was observed that the reaction order dramatically decreased from first order to zero order as the reaction temperature increased from 45 to 75C. It means that the oxidation process is more concentration dependent at lower temperatures. However, according to our observations, reducing the tocopherol content during interesterification does not inversely affect the oxidative stability of cottonseed, palm and soybean oils, but interesterification reduces the nutritional value of oils. α‐Tocopherol has the highest vitamin E activity. Tocopherol supplementation of interesterified oils with equal amounts of eliminated tocopherols can be applied by related industries. Tocopherol loss is the most important and probably the only known disadvantage of chemical interesterification.
Cake is one of the most loved bakery products. Formula constituents affect cake quality. Especially, fat in the formula alters internal and external attributes, shelf-life and nutritional value of the cake. The type of fat is important for conscious consumers for health reason. Chemically interesterified palm (in-es PO) and cottonseed oils (in-es CO) were used instead of hydrogenated cake shortening (HS) in this study. The layer cakes were prepared according to modified American Association of Cereal Chemists Method. Physical characteristics such as batter density and consistency, cake volume, crust and crumb properties and sensory attributes such as moistness, flavour, mouth-feel of cake samples prepared with chemically interesterified (in-es) and non-interesterified palm and cottonseed oil (non-in-es) blends at 0, 25, 50 and 100 (wt%) levels were compared with that of the layer cake prepared with HS. The total trans fatty acid (TFA) content of regular cake shortening was high (14.38%). The experimental shortenings have zero TFA. An increase in the level of CO in the interesterified and non-interesterified blends lowered the solid fat content, thus increasing batter density and fluidity. Favourable cakes close to the standard cake have been made by using in-es (PO:CO) at the ratio of 75:25 and 50:50 (wt%) without any significantly adverse change in sensorial properties. The results indicated that interesterification can be successfully applied in cake shortening production, resulting in decrease in the consumption of TFA.
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