Effects of Pleurotus eryngii polysaccharides on bacterial growth, texture properties, proteolytic capacity, and angiotensin-I-converting enzyme–inhibitory activities of fermented milk

Abstract

Pleurotus eryngii is one of the most favored oyster mushrooms and contains various beneficial bioactive compounds. Polysaccharide extracted from P. eryngii (PEPS) was added as a natural-source ingredient to milk before fermentation, and the effects of additional PEPS on fermented milk were investigated in this study. The PEPS were extracted and added to reconstituted skim milk (12%, wt/vol) at 0.5, 0.25, and 0.125% (wt/vol) and fermented by a non-exopolysaccharide-producing strain, Streptococcus thermophilus Australian Starter Culture Collection (ASCC) 1303 (ST 1303), or an exopolysaccharide-producing Strep. thermophilus ASCC 1275 (ST 1275). Bacterial growth, texture properties, microstructure, proteolytic capacity, and angiotensin-I-converting enzyme-inhibitory activities of fermented milk (FM) were determined during refrigerated storage at 4°C for 21d. Viable counts of starter bacteria in FM with 0.5% PEPS added were the highest. Changes in pH were consistent with changes in titratable acidities for all samples. The FM samples with added PEPS showed denser protein aggregates containing larger serum pores in confocal micrographs compared with those without PEPS at d 0 and 21during refrigerated storage. The values for spontaneous whey separation of FM with added PEPS were significantly higher than those of FM fermented by ST 1303 or ST 1275 without PEPS. The proteolytic activities of ST 1303 of FM with added PEPS were higher than those of FM fermented by ST 1303 without PEPS. The FM with added 0.125% PEPS had similar angiotensin-I-converting enzyme-inhibitory activity to that fermented by ST 1303 without PEPS; both were higher than those of other samples during refrigerated storage. Firmness and gumminess values of FM with added PEPS were higher than those of FM fermented by ST 1303 or ST 1275 without PEPS.

Ropy exopolysaccharide‐producing Bifidobacterium longum YS108R as a starter culture for fermented milk

“…The data showed no significant correlation between EPS concentration and level of whey syneresis or WHC, which suggested that the effect of EPS may be related to the physical and chemical properties of the EPS which are determined by molecular mass and subunit structure, in addition to the interaction between EPS and milk protein. It has been reported that Pleurotus eryngii polysaccharides could accelerate spontaneous whey separation of fermented milk, which could be as a result of the protein aggregation and decreased casein in milk led by the addition of P. eryngii polysaccharides (Li & Shah, ). In our study, the different effects of YS108R and C11A10B may be due to the individual properties of the EPS produced by each strain, which may interact with milk protein in a different manner and then affects the gel structure.…”

Biotechnological, nutritional and therapeutic uses of Pleurotus spp. (Oyster mushroom) related with its chemical composition: A review on the past decade findings

“…This has promoted, especially in the past years, an increasing interest in extracting ingredients from foods such as mushrooms and in developing functional foods (Li & Shah, 2015). polysaccharides, small peptides and proteins) and low (e.g.…”

Development of a simple, low-cost and eurytopic medium based on Pleurotus eryngii for lactic acid bacteria

“…Pleurotus eryngii is a kind of favored oyster mushroom, and contains rich nutrients, such as protein, fiber, carbohydrates, vitamins and minerals (Cohen et al 2002; Li and Shah 2015). Li and Shah (2015) found that polysaccharide extracted from P. eryngii could promote the proliferation of Streptococcus thermophilus in fermented milk, and enhance its viability rate during refrigerated storage at 4 °C (Li and Shah 2015).…”

“…Li and Shah (2015) found that polysaccharide extracted from P. eryngii could promote the proliferation of Streptococcus thermophilus in fermented milk, and enhance its viability rate during refrigerated storage at 4 °C (Li and Shah 2015). In the previous study, we found that L. lactis subsp.…”

“…Currently, P. eryngii has been extensively cultivated in the world (Zhao et al 2013; Li and Shah 2015). During the cultivation, there is plentiful low-cost inferior mushroom.…”