THE ADDITION OF OAT FIBER AND NATURAL ALTERNATIVE SWEETENERS IN THE MANUFACTURE OF PLAIN YOGURT

Calorie-reduced yogurts that were fortified with 1.32% oat fiber were prepared from lactose-hydrolyzed milk, alone and supplemented with 2 a nd 4% sucrose or with 1.6, 3.6, and 5.5% fructose. Treated samples wer e compared with unsweetened yogurt and with yogurts sweetened with 2, 4, and 6% sucrose. Addition of 5.5% fructose increased fermentation ti me by 60%, slowing down the production of lactic, pyruvic, acetic, and propionic acids and the consumption of hippuric and erotic acids. Lac tose hydrolysis had an inhibitory effect on starter activity at the be ginning of fermentation and a stimulatory effect at the end of ferment ation. Fiber addition led to increases in concentrations of acetic and propionic acid. Lactobacilli counts were lower in samples treated wit h fructose. The use of hydrolyzed milk had a stimulatory effect on tot al bacteria and lactobacilli counts throughout the cold storage period . After 28 d of storage, lactobacilli counts were consistently higher in fiber-fortified yogurts, but total bacteria counts were lower. Appa rent viscosity increased with the addition of sweetener and fiber. Lac tose-hydrolyzed and fructose yogurts had the highest viscosity values. Samples sweetened with sucrose received the highest scores for flavor . Fiber addition decreased overall flavor quality. The lactose-hydroly zed yogurts received the highest flavor scores, independent of fiber f ortification. Fiber addition improved the body and texture of unsweete ned yogurts but lowered overall scores for body and texture in yogurts sweetened with sucrose.