Abstract
Flammulina velutipes is one of the most important edible mushrooms, which quickly decays with a short shelf life. However, little is known about the effect of ɛ-polylysine (ɛ-PL) or nisin on the survival of Lactococcus lactis (L. lactis) during the storage at constant temperatures. The objective of this study was to investigate the effect of ɛ-PL or nisin on the growth of L. lactis and background (BK) microorganisms in fresh Flammulina velutipes fruiting bodies (FVFB) and develop mathematical models to predict their growth behavior. The effect of ɛ-PL (0.15 and 0.30 g/kg) or nisin (0.10 and 0.20 g/kg) on the growth of L. lactis and BK microorganisms in FVFB was analyzed at 4, 16, and 20°C. The lag phase of L. lactis was extended, and the specific growth rate was decreased by increasing concentrations of ɛ-PL or nisin and lowering the temperature. The results showed that ɛ-PL or nisin could control the growth of L. lactis in FVFB. However, the growth of BK microorganisms was not affected by ɛ-PL or nisin. The growth of L. lactis and BK microorganisms could be successfully described by the reparameterized Gompertz and no lag phase models, respectively. Additionally, ɛ-PL or nisin could maintain the quality of FVFB by preventing weight loss, color-changing, and decreasing soluble solid content in FVFB at 4°C. These results suggest that ɛ-PL or nisin in combination with low temperature may inhibit the growth of L. lactis in FVFB and prevent the decrease in the quality of FVFB.
Highlights
Flammulina velutipes fruiting body (FVFB), known as golden needle mushroom or winter mushroom, is one of the most important edible mushrooms widely cultivated and consumed in China, Japan, and Korea [1]
Bacterial Cultures and Preparation. e culture of L. lactis was isolated from Flammulina velutipes fruiting bodies (FVFB) and identified by 16S RNA gene amplification. e isolated L. lactis was transferred to 10 mL of Luria–Bertani broth (Huankai Microbial Co., Ltd., Guangzhou, China) and incubated at 37°C for 20 h
The bacteria pellet was harvested by a refrigerated centrifuge (4°C; Sigma-Aldrich Co., MO) at 4500 rpm for 15 min and washed three times using 10 mL of 0.1% sterile peptone water (PW; Huankai Microbial Co., Ltd., Guangzhou, China)
Summary
Flammulina velutipes fruiting body (FVFB), known as golden needle mushroom or winter mushroom, is one of the most important edible mushrooms widely cultivated and consumed in China, Japan, and Korea [1]. Compared to other commercial edible mushrooms, such as Agaricus bisporus, Pleurotus eryngii, Pleurotus geesteranus, and Volvariella volvacea, FVFB requires a simple cultivation technique and has unique advantages of fast fruiting and high yield [2, 3]. FVFB contains a variety of bioactive compounds, such as polysaccharides, essential amino acids, glycoproteins, and sesquiterpenoids. Because of the aforementioned high nutritional value, medicinal properties, and favorable taste, an increasing number of FVFB have been widely consumed. As fresh FVFB is nutritious and contains high moisture content, it favors microorganisms (covering pathogenic and spoilage bacteria) propagating, leading to its decay and short shelf life
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