Thiobarbituric acid‐reactive substances (TBARS) values, hexanal content, and sensory analysis were used to evaluate the effectiveness of selected natural antioxidants to reduce warmed‐over flavor (WOF) development in cooked ground beef. The control without added antioxidant showed the highest TBARS value, hexanal content, and WOF scores. Grape seed extract (ActiVinTM) and pine bark extract (Pycnogenol®) significantly improved the oxidative stability of cooked beef. Compared to the control, ActiVinTM, Pycnogenol®, and oleoresin rosemary reduced the hexanal content by 97%, 94% and 73% after 3 d of refrigerated storage, respectively. WOF scores showed a similar pattern as TBARS values and hexanal contents. TBARS values, WOF scores, and hexanal contents were all well correlated.

Bifidobacteria are probiotic organisms that improve the microbial balance in the human gut. They can be incorporated as live cultures in fermented dairy foods, including yogurt, for transmission to humans. Because bifidobacteria are sensitive to high acidity, their viability in yogurt is limited. The objective of the present study was to investigate the effect of microencapsulation on the viability of bifidobacteria in yogurt during refrigerated storage for 30 d. Live bifidobacterial cells were encapsulated in kappa-carrageenan. Cell enumeration, determination of titratable acidity and pH, quantitation of lactic and acetic acids, and sensory evaluation (consumer test) were carried out on the yogurt samples. Microbiological results showed a decline of 78 and 70.5% in the population of Bifidobacterium longum B6 and B. longum ATCC 15708, respectively, for the treatments containing nonencapsulated cells. No difference in bifidobacterial population was observed in the encapsulated treatments. The acetic acid content in the yogurt with nonencapsulated bifidobacteria was higher than that in the plain yogurt (control) and encapsulated treatments. The increase in lactic acid content during storage was not different among the various treatments for B. longum B6, but was greater for nonencapsulated than encapsulated B. longum 15708 and the control. Consumers judged the nonencapsulated treatment as the most sour, which was likely due to the higher acetic acid content. Consumers preferred the control and nonencapsulated treatments over the encapsulated treatment. Microencapsulation appears to increase the viability of bifidobacteria in yogurt. This technique can be used to transmit bifidobacteria via fermented products provided that sensory characteristics of the product are improved or maintained.

Profiles of genistein, daidzein, genistin, daidzin, and their acetyl- and malonyl-beta-glycosides were determined in tofu as affected by temperature and time. Tofu was heated in water at 80, 90, and 100 degrees C for 0 (control), 10, 20, 30, and 40 min, and the contents of the isoflavones of interest were quantified using reversed-phase HPLC. Total isoflavone content decreased most likely due to leaching of isoflavones into the water. Because the content of the isoflavones of the genistein series was little affected by the treatments, the decrease in the total isoflavone content was almost exclusively due to a decrease of the daidzein series. Changes in the profile of the daidzein series suggest little decarboxylation of the malonylglycoside to the acetylglycoside, but considerable de-esterification of the malonyl- and acetylglycoside to the beta-glucoside. Strongly temperature dependent decreases of the aglycon suggest possible thermal degradation of daidzein in addition to losses due to leaching.

The effects of milk fat concentration on flavor perception of vanilla ice cream (with 0.5 to 10% fat) were studied by sensory analyses. The percentage of free vanillin in the ice cream was determined by HPLC. The HPLC data showed that the amount of free vanillin decreased when fat content increased. Perceptions of vanilla flavor and sweetness were evaluated by a trained panel using time-intensity methodology. No significant difference was found in sweetness perception. Among 11 time-intensity parameters for vanilla flavor perception, the panel found a significant difference only in the time required to reach maximum vanilla intensity. However, free-choice profiling and a consumer preference panel showed, respectively, that, as fat content was increased, sensory quality improved, and overall preference increased.

The organic acids profile in femented dairy foods is an indicator of the metabolic activity of added bacterial cultures. These acidr act as natural preservatives and contribute to the characteristic sensory properties. This study was done to determine the fleet of encapsulation on the metabolic activity of probiotic supplements, i. e. bifidobmeria, in plain yogurts. Metabolically active bijidohcteria may increase the concentration of certain organic acids, mainly acetic and propionic acids, which might lead to decreased acceptability of the product. Changes in the proBles of organic acids were determined in plain set and stirred-type yogurts containing the starter culture and microencapsulated and nonencapsulated probiotic strains of either Bifidobacterium longum B6 or B . longum ATCC 15708. Ion-exchange high-pevormance liquid chromatography was used for the separation and quantification of the organic acih. Concentrations of acetic and lactic acid increased during storage, while those of citric and uric acid remained stable. No particular pattern was observed for propionic or butyn'c acid, while pyruvic acid initial& decreased and then increased during storage.