Followed extraction of β-glucan and mannoprotein from spent brewer's yeast (Saccharomyces uvarum) and application of the obtained mannoprotein as a stabilizer in mayonnaise

The aim of this study was to evaluate the viability of a novel method to extract both β-glucan and mannoprotein (MP) from the cell wall of spent brewer's yeast (Saccharomyces uvarum), particularly with the obtainment of MP by an additional step in a non-degrading procedure to extract β-glucan. The structure and composition of both obtained polymers were characterized, and the potential application of the MP as an emulsifier and stabilizing agent to replace xanthan gum (XG) in mayonnaise formulations was assessed. The yield obtained for β-glucan and MP was 10% and 4%, respectively. Infrared and nuclear magnetic resonance spectroscopy of β-glucan indicated a typical pattern of a glucose polymer with β-linkages. Analyses of the carbohydrate portion of MP revealed a retention factor of only 0.45, which indicates the presence of mannose; analyses of the protein portion of MP revealed 58-kDa and 64-kDa proteins that are largely composed (mg/g) of the amino acids valine (8.9%), aspartic acid (8.2%) and leucine (6.9%). The pH of the mayonnaise formulations containing different concentrations of MP (MP1: 0.6 g of MP/100 g; MP2: 0.8 g of MP/100 g; MP3: 1.0 g of MP/100 g) did not change (P ≥ 0.05) during 28 days of refrigerated storage. The stability of the MP1, MP2 and MP3 formulations increased during the assessed time (P ≤ 0.05) and after 28 days showed values higher than the formulation prepared with XG. All mayonnaise formulations prepared with MP exhibited high lightness (L* value) and a tendency toward decreased yellow color (b* value) during storage. Moreover, the formulations prepared with MP received similarly high scores (P5) for aroma, color, flavor and the overall evaluation without differences from that prepared with XG. Regarding the intent to purchase, the tasters generally reported the desire to purchase all of the tested mayonnaise formulations. The results presented herein demonstrated the feasibility of the proposed procedure to obtain both β-glucan and MP from spent brewer's yeast with a high yield and satisfactory purity. The obtained MP demonstrated good emulsifying and stabilizing properties, and its application to replace XG in the formulation of mayonnaise presented no negative effect on the sensory attributes of the product during refrigerated storage. Industrial relevance S. uvarum has been an interesting biotechnological tool for the production of beer using low fermentation, resulting in production of high amounts of brewer's yeast, which is commonly discarded. β-Glucan and mannoprotein (MP) obtained from spent brewer's yeasts have presented interesting biological properties, which could be applied for food production and conservation. Present study provides novel and valuable information concerning the viability of a followed method to extract β-glucan and MP from the cell wall of spent brewer's yeast (S. uvarum) discarded after fermentation processes, chiefly about the specific isolation of MP using an additional step in a non-degrading procedure that included sonication and proteolysis to extract β-glucan. The obtained MP revealed interesting emulsifying and stabilizing properties, and its use for the formulation of mayonnaise had no negative effect on the sensory properties of the product during refrigerated storage.