The Addition of Oat Fiber and Natural Alternative Sweeteners in the Manufacture of Plain Yogurt

¹ Instituto de Productos Lácteos de Asturias Consejo Superior de Investigaciones Científicas, Carretera de Infiesto, sin número, Apartado de Correos 85, 33300 Villaviciosa, Asturias, Spain
² Department of Dairy Science, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803

Calorie-reduced yogurts that were fortified with 1.32% oat fiber were prepared from lactose-hydrolyzed milk, alone and supplemented with 2 and 4% sucrose or with 1.6, 3.6, and 5.5% fructose. Treated samples were compared with unsweetened yogurt and with yogurts sweetened with 2, 4, and 6% sucrose. Addition of 5.5% fructose increased fermentation time by 60%, slowing down the production of lactic, pyruvic, acetic, and propionic acids and the consumption of hippuric and orotic acids. Lactose hydrolysis had an inhibitory effect on starter activity at the beginning of fermentation and a stimulatory effect at the end of fermentation. Fiber addition led to increases in concentrations of acetic and propionic acid. Lactobacilli counts were lower in samples treated with fructose. The use of hydrolyzed milk had a stimulatory effect on total 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. Apparent viscosity increased with the addition of sweetener and fiber. Lactose-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-hydrolyzed yogurts received the highest flavor scores, independent of fiber fortification. Fiber addition improved the body and texture of unsweetened yogurts but lowered overall scores for body and texture in yogurts sweetened with sucrose.

Key Words: fiber • fermentation • yogurt quality • lactose hydrolysis

Submitted on August 12, 1996
Accepted on October 14, 1997