Permeate is the by‐product of the process of ultrafiltration in a kind of cheese making process in which a semipermeable membrane filters the liquid. It mainly contains 4.5%–4.8% lactose and 0.44%–0.47% mineral salts which make it a safe disposal issue. This study was conducted to use permeate and its lactose as an alternative to sugar, and to use these useful permeate compounds in an optimized orange juice formulation. Milk permeate, as a waste disposal of dairy companies, was applied in lactose hydrolyzed form as the cost effective sugar and water substitution in production of orange juice. The RSM optimization method was applied for formulating beverage mixture. The heated and nonheated permeate samples were incubated with β‐glycosidase enzyme in three thermal ranges (35, 40, and 45°C), 3 time intervals (60,150, and 240?min), and 3 enzyme levels (0%, 0.1%, and 0.2%). The degree of hydrolysis was determined by MilkoScan analyzer. In the next step, optimization of orange juice was accomplished with a mixture of sugar (10%–40%) and hydrolyzed permeate (10%–40%) with specific Brix through RSM statistical design. The physicochemical properties and sensory evaluation were measured during 8?weeks of storage. At the first stage of the study, the heated sample with 0.1% enzyme density, which was incubated for 150?min at 40°C, was yielded the best result. At the second stage, which was the juice production and evaluation, the statistical analysis showed increasing trend of pH and sugar content, but density and vitamin C showed a decreasing trend during storage time (p??.05). The optimal condition was obtained in taking 35% permeate and 41?days of storage in which the values of formalin, vitamin C, and sensory tests were in the highest levels.
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