CHEMICAL, MICROBIOLOGICAL AND SENSORY PROPERTIES OF PLAIN NONFAT YOGURT

Chemical and microbiological properties of plain nonfat yogurt were de termined after 2, 6 and 12 days refrigerated storage. Sensory properti es were determined after 6 days storage. Viable culture bacteria conce ntrations ranged from 140 to 8,000 x 10(6)/g and ratios of lactobacill us to streptococcus ranged from 0. 18 to 15.4. Chemical criteria used to characterize products included: pH, titratable acidity, lactic and four other organic acids and lactose by HPLC, and 23 major volatile or ganic compounds by dynamic headspace analysis. Lactic acid concentrati ons ranged from 7.5 to 9.9 mg/g. Major flavor volatiles in all yogurts included: acetaldehyde, heptane, acetone, diacetyl, and benzothiazole . Untrained sensory panels showed differences for flavor, aroma and ac ceptability.