A functional fermented beverage formulated with whey protein concentrate

Abstract

Over the years, numerous efforts have been made to transform whey, generated as by-product of the cheese industry, into a suitable product for food use. Whey constitutes about 90% of the milk volume used for cheese manufacture retaining 55% of milk nutrients. Whey proteins are recovered by ultrafiltration and spray dried to produce powdered whey protein concentrate (WPC). The main whey protein, β-lactoglobulin (BLG), is the major cause of milk allergy in children under three years old. Lactic acid bacteria have been extensively used in the development of dairy foods and are able to degrade milk proteins. This work addressed the development of a fermented whey-based drink with reduced BLG content. Cell viability, lactose consumption, lactic acid production, proteolytic activity, amino acid release and BLG degradation by the strains Lactobacillus acidophilus CRL 636, Lb. delbrueckii subsp. bulgaricus CRL 656 and Streptococcus thermophilus CRL 804, as single or mixed (SLaB) starter cultures were evaluated in WPC (10%, w/v) incubated at 37°C for 12 h. The fermented WPC was then mixed with peach juice and calcium lactate (2%, w/v) and stored for 28 days at 10°C. During fermentation, single cultures grew 2-3 log cfu/ml and produced between 12 and 101 mM of lactic acid as consequence of lactose consumption (4-42 mM). Lb. delbrueckii subsp. bulgaricus CRL 656 was the most proteolytic strain (576 µg/ml Leu) and released the branched chain essential amino acids Leu (16 g/ml), Ile (27 g/ml) and Val (43 g/ml) and S. thermophilus showed the lowest proteolytic activity (70 g/ml Leu). All strains degraded BLG in a range of 8-27% after 12 h. The starter culture SLaB grew 3 log cfu/ml, showed a marked pH reduction, produced 84 mM of lactic acid and displayed high proteolytic activity (484 g/ml Leu) releasing Leu (13 g/ml), Ile (18 g/ml) and Val (35 g/ml), and hydrolyzed 16% of BLG. The addition of peach juice improved the organoleptic characteristics of the fermented WPC and calcium lactate maintained the drink pH stable during the shelf-life, no contamination being observed after 28 days. During this period, a decrease in cell viability was observed for all strains being more pronounced for Lb. acidophilus CRL 636 (0.7 log cfu/ml). No significant changes in amino acid concentration were detected. These results evidence that WPC fermentation by selected lactic acid bacteria might be used for developing novel functional beverages with improved properties such as reduced BLG content and increased branched-chain essential amino acids.