Development of Pleurotus ostreatus yogurt

Pleurotus ostreatus is a kind of edible fungus which is easy to cultivate, high yield and deeply loved by the general public. Pleurotus ostreatus is tender in meat, delicious in taste and rich in nutrition. every 100g of dried mushrooms contains protein 23mur28g, fat 1.42rel 2.87g; protein contains 18 kinds of amino acids, and the contents of 8 kinds of essential amino acids and 2 kinds of semi-essential amino acids (arginine and histidine) account for about 40-50% of the total amino acids, as well as phosphorus, potassium, iron, zinc, copper and other trace elements and rich Vc. Pleurotus ostreatus has high medicinal value and has the effect of anti-tumor and improving immunity. Pleurotus ostreatus also contains taurine, γ-aminobutyric acid and other substances that can promote human health. Frequent consumption of Pleurotus ostreatus can reduce cholesterol, blood pressure and improve health. Yogurt is a kind of functional food which integrates nutrition and health care. It not only has a unique flavor, but also contains a large number of lactic acid bacteria and their decomposition products, which can inhibit the survival of other harmful bacteria in the stomach and intestines, promote digestion, prevent and cure diseases, and improve health. Therefore, after adding Pleurotus ostreatus to milk and fermenting with lactic acid, the product with the unique dual nutrition and health care function of Pleurotus ostreatus and yoghurt can be obtained.

The main results are as follows: (1) fresh Pleurotus ostreatus with no peculiar smell, no mildew and no mechanical damage, and fresh milk in accordance with GB6914-86 standard were selected. Sucrose is selected to meet the national standards. Strains: Lactobacillus bulgaricus (L.B) and Streptococcus thermophilus (S.T), respectively, were activated for 5 generations to make working starter (L.B:S.T = 1 ∶ 1). The equipment used includes beater, high pressure homogenizer, drying box, constant temperature incubator, super clean workbench, refrigerator and so on.

(2) preparation of Pleurotus ostreatus juice: fresh Pleurotus ostreatus to eradicate impurities, rinse in clean water, cut into pieces, put into pot and add a little water, add 0.2% citric acid and 0.1% VcMaguire 95 100 ℃ to heat for 30 minutes and cool quickly; beat the cooled Pleurotus ostreatus with the same amount of water with a beater, and finally filter Pleurotus ostreatus juice with 120 mesh silk cloth. Technological process of Pleurotus ostreatus yoghurt: ① fresh milk → filtration purification → preheating → mixed homogenized → sterilization → cooling ② lactic acid bacteria pure culture → mother starter → working starter → inoculated into the cooling semi-product of ① → sub-packed → constant temperature culture → refrigerated → finished product process: according to the processing technology of ordinary yogurt, that is, 6% white sugar and different amounts of Pleurotus ostreatus juice are added when the milk temperature is 60 ℃. In order to prevent the addition of Pleurotus ostreatus juice to reduce the dry matter content of milk, add 3% milk powder and mix evenly. After homogenization (pressure 18-20Mpa), heat up to 90 ℃ 95 ℃, keep 5 ℃ sterilized, quickly cool to 40 ℃, add 3% working starter (L.B:S.T is 1:1) to constant temperature fermentation until solidified at 42 ℃, refrigerate in 4 ℃ 6 min refrigerator. (3) the results showed that with the increase of the amount of Pleurotus ostreatus juice, the clotting time tended to shorten, especially when the addition amount of Pleurotus ostreatus juice reached more than 20%, the effect was obvious. Therefore, when making yoghurt, the addition amount of Pleurotus ostreatus juice can choose more than 15%. When the addition amount of Pleurotus ostreatus juice was in the range of 5%, 30%, the acidity of the product increased with the increase of the addition amount; with the same addition, the acidity increased during fermentation, cooling and cold storage, in which the acidity increased obviously during fermentation, and the change of acidity within 3 days of cold storage was significantly greater than that after 3 days. This is due to the decrease of cell vitality under cold storage conditions and the further aging or death of bacteria caused by metabolites such as organic acids over time, and when the addition is 15% and 20%, the acidity during cold storage is close to that of ordinary yogurt. The highest acid value of the finished product is 104.23 °T and the lowest is 92.19 °T, which conforms to the regulations of GB2746-85. Pleurotus ostreatus juice is in the range of 5% to 30%, the more the amount of Pleurotus ostreatus juice is added, the higher the number of living bacteria in the product is, and the decrease of the number of bacteria in the product during cold storage decreases with the increase of the adding amount. This may be due to the fact that the nutrients in Pleurotus ostreatus juice promoted the growth of bacteria, but the addition of Pleurotus ostreatus juice was more than 30%, and the number of living bacteria decreased during cold storage. Pleurotus ostreatus yogurt is refrigerated in 4 ℃ 6 min refrigerator for 24 hours. The results showed that the yogurt with 15-20% mushroom juice had good flavor, no peculiar smell and milky white color.

(4) conclusion 1) 15% 20% flat mushroom juice yoghurt does not have any peculiar smell compared with ordinary yogurt, has the unique smell of pure lactic acid fermentation, the tissue state is uniform and delicate, and the color is similar to ordinary yogurt. 2) within 7 days of storage in the refrigerator, the yogurt was in good organization and no whey precipitated, but more than 7 days, whey precipitated. It is recommended that the storage time of Pleurotus ostreatus yogurt in the refrigerator should be less than 7 days. 3) adding 1520% Pleurotus ostreatus juice, 6% sucrose, 3% milk powder and 3% inoculated starter to fresh milk can produce high quality Pleurotus ostreatus yoghurt according to the production process of ordinary yoghurt.