Fresh ground beef containing 20 and 25% fat was either treated with 0.01, 0.05 or 0.10% crystalline ascorbic acid or remained as non-treated controls. Samples were displayed in polyvinyl chloride (PVC) film for up to 10 d (24 h/d) at 2 to 3°C under 1076 lux G. E. Natural light. Measures of display life included visual color scores, reflectance measurements, sensory panel scores, thiobarbituric acid (TBA) values and microbial standard plate counts (SPC). At days 1, 3 and 5 of display, average and worst point visual color scores were judged brighter for all ascorbic acid treatments compared to controls. Lower metmyoglobin percentages, higher %R630nm/%R580nm and higher CIE a * readings at days 3, 5 and 10 for the ascorbic acid-treated product supported visual color results. Higher fat (25%) and higher ascorbic acid levels (0.05 and 0.10%) gave brighter visual color responses at 5 d of display than the 20% fat product and that containing 0.01% ascorbic acid. More intense sensory panel beef flavor was associated with the 0.05 and 0.10% ascorbic acid treatments. More off-flavor was found in the higher fat product (25%). TBA values were not different for fat level comparisons, but were lower for the 0.05 and 0.10% ascorbic acid treatments. At day 5 of display, SPC were not affected by ascorbic acid treatment. The 25% fat product had lower SPC at day 5.
We compared yield and curd characteristics of cottage cheese made by the short-set culture and direct-acid-set methods using three skim milk protein concentrations. 3.1, 3.5 and 3.9 ± .1%. For each method of manufacture, approximately 380 kg of the same skim milk were set per experimental vat. Representative samples of whey, wash water and curd were analyzed and the total quantities of each were measured. Solids and protein recovered in whey, wash water and curd were related to yields for each method. The same curd samples also were used to measure curd size distribution, curd firmness and dressing retention. Analysis of variance showed highly significant differences in curd yield between the two methods when the three protein concentrations were considered. There was approximately 5% more yield when cottage cheese was made from skim milk containing 3.1 or 3.5% protein, using the direct-acid-set method. This yield advantage was less than 1% when the skim milk contained 3.9% protein. Curd firmness did not differ significantly between methods (p < .01). Curd from the 3.1% protein-skim milk, however. was firmer (p < .01) than that from either 3.5 or 3.9% protein-skim milk. Direct-acid-set curd was more uniform in size than that of the short-set culture curd. It retained dressing better only when made from 3.1% protein skim milk, and when 1.25 × the normal amount of dressing was used.