Optimization and investigation on physicochemical, sensory and microbial quality of permeate-based probiotic lemon beverage

Nowadays an increasing demand for whey products particularly whey protein concentrate (WPC) and whey protein Isolate (WPI) resulted in considerable amount of permeates production, which its rejection causes environmental pollution. The bioconversion of whey and permeate is an appealing procedure regarding to human nutrition, particularly for its functional properties. Functional foods are foodstuffs, which have specific functions in the human, resulting health benefits besides energy and nutrients. Fermented dairy products containing probiotic bacteria are group of functional foods, which have received increasing attention in recent years, including the development of the market with large commercial and research interests. Production of probiotic beverages from permeate could be considered as a simple solution to prevent permeate rejection and produce an economical product with appropriate functional properties. Definitely, dairy products are the foremost vehicle for probiotic supplementation. However, other nondairy probiotic products such as fruit and vegetable juices have been shown to afford health benefits. Therefore, the aim of this study was optimizing formulation of permeate-based lemon juice beverage and producing probiotic beverage from optimized beverage.
Based on primary experiments, lemon juice beverages containing permeate were produced with different concentrations of water (19.77, 30, 45, 60, and 70.22 ml), permeate (12.95, 30, 55, 80 and 97.04 ¬ml) and LEMON juice concentrate (5.95, 8, 11, 14, and 16.04 g). To estimate the impact of these independent variables and determination of optimized sample (non-probiotic beverage), response surface methodology (RSM) founded on central composite design (CCD) was applied. According to CCD design, 20 tests with six replicates as the center points were performed. Quadratic polynomial model were considered for the relationship between the predicted responses with the independent variables. The optimization was performed based on physicochemical (pH, acidity, total solids and brix) and sensory (taste, color, odor, after taste and total acceptability) characteristics of beverage samples. At the second stage, the best sample was inoculated with Lactobacillus acidophilus (La5) and its physicochemical properties, antioxidant capacity, sensory attributes and probiotic cell count were monitored during a 28-day storage period under refrigerator temperature (4°C).
The results showed that all fixed factors, i.e. amount of water, permeate and lemon juice concentrate, had significant impacts on the physicochemical and sensory properties of lemon juice-permeate beverages. By increasing the amount of water up to 45 ml, permeate up to 55 ml and lemon juice concentrate up to 11 g in the formulation, the taste, after taste and total acceptability scores were significantly (p