Study On Preparation Technology Of Pea Yoghurt And Influencing Factors Of Product Quality

Plant-based yogurt,also known as Non-dairy yoghurt,is an important part of plant-based food which is popular all over the world.Compared with soybean,pea has more obvious natural ecological attributes,and its nutritional value is superior to soybean in some aspects.High-quality pea yogurt will have a good market prospect.On the other hand,due to the odor of peas and the composition of pea protein,there is no market-approved pea yoghurt product in China.At present,there are few reports on the preparation of pea yoghurt from pea milk in domestic and foreign related studies,and plant milk is the starting material of most plant-based yoghurt.This topic focuses on the effects of pretreatment of pea raw materials on the quality of pea milk and pea yoghurt,and on this basis,discusses the effects of starter cultures and fermentation conditions on the quality of pea yoghurt.The research results will provide a basis for the development of pea yoghurt technology.The subject mainly includes the following contents:Firstly,the milk was extracted from untreated peas and fermented by lactic acid bacteria,and then compared with soy milk and soy yogurt.The results showed that both pea milk and soy milk had lactic acid bacteria fermentability,but pea milk had stronger buffering capacity,that is,when reaching the same fermentation end point(p H 4.7),the titratable acidity of pea yoghurt was 10°T higher than that of soy yoghurt.The content of volatile components in soy milk and soy yoghurt was significantly lower than that in pea milk and pea yoghurt,and the total content of volatiles in pea milk was 4.9 times that of soy milk.The taste and smell score of soy yoghurt was significantly higher than that of pea yoghurt(p<0.05).When pea milk and soy milk were mixed and fermented,the fermentation characteristics of the mixed system became worse with the increase of soy milk ratio,but the texture characteristics of the fermented products were better,and the scores of color,smell and taste were higher.When the mixing ratio of soy milk and pea milk reached to 3:1,the sensory score of fermented yoghurt was closed to that of soy yoghurt.Then,the effects of pea pretreatments on the quality of pea milk and pea yoghurt were investigated.The dried peas were soaked in alkaline water(A),dry peeled-soaking in alkaline water(B),blanched in boiling water-peeled-alkaline soaked(C)and blanched in boiling water-peeled-alkaline soaked-germ removed(D)to prepare pea milk.The effects of treatment methods on basic components,protein composition,volatile components,fermentation characteristics of different pea milks,texture characteristics,volatile flavor and sensory evaluation of different pea yoghurts were investigated.It was found that the total content of volatile flavor compounds in pea milk D was the lowest,which was 29.78?g/L.Compared with untreated peas,the total volatile content of pea milk decreased by 95.63%after blanching in boiling water-peeling-alkaline soaking-degerming(method D).On the basis of selecting method D,the effects of starter cultures and fermentation technology on the quality of pea yoghurt were further discussed.Firstly,the effects of different carbon and nitrogen sources on the quality of pea yoghurt were studied.It was found that sucrose,glucose and soy peptide could improve the fermentation rate of pea milk fermentation base material(only 4 h to reach the fermentation end point).Then,the fermentation conditions of 6 kinds of commercial starter cultures in pea milk base were compared,and it was found that the fermentation characteristics,texture and sensory evaluation of yoghurt were quite different with different starter cultures.The effect of protein concentration on yoghurt quality was investigated.It was found that there was a significant positive correlation between protein concentration and texture parameters of yoghurt(R~2?0.97).Moreover,the higher the concentration of protein,the higher the titratable acidity of pea yoghurt when reaching the fermentation end point of p H(4.7).Adding buffer salt can increase the acidity of pea yoghurt by at least 15°T.When adding 0.1%disodium hydrogen phosphate and 0.1%sodium citrate,the number of viable lactic acid bacteria in pea yoghurt was twice that of the control group.Finally,the technological process of pea yoghurt based on blanching in boiling water-peeling-alkaline soaking-degerming pea treatment was put forward,and the material balance,composition of processing by-products and recycling suggestions were given.