Preparation Of Asparagus Powder And Akebia Trifoliata Pectin And Effect Of Their Supplementation On The Quality Of Yogurt

Low-fat yogurt has been popular as a result of its nutritional value and health benefit,while the lack of fat is easily leading to the poor texture,whey separation,and poor taste.Asparagus and Akebia trifoliata are both medicinal and edible homologous plants with rich nutrition and high health care function.Asparagus is highly seasonal,easy to be lignified and putrefied,and low in intensive processing,which limits the development of asparagus industry.What's more,the peel of Akebia trifoliate,more than 60%of its fruit weight,is often discarded,causing a great waste of resources and environmental pollution.In this experiment,the asparagus power was maded by vacuum freeze-drying,the pectin was extracted from the peel of Akebia Trifiliata,and the effect of supplementing asparagus power and pectin on quality of the low-fat yogurt was investigate.The main conclusions are as follows:1.Effect of vacuum freeze drying on quality of asparagus and asparagus yogurt:comparing asparagus powder?P?with fresh asparagus?F?through vacuum freeze drying according to their dry matter content,it is found that there were no siginificant difference among the total protein,reducing sugar and the total phenols content of P and F.What's more,the rutin and total sugar have high retention rates of 98.77%and 83.89%.Therefore,vacuum freeze drying can effectively preserve nutrients in fresh asparagus.Based on the control group,the sensory of yoghurt adding with F and P?FY and PY?were improved,and it's the same as the content of Streptococcus thermophilus,lactic acid bacteria,reducing sugar,total sugar,flavonoids,polyphenols,water-holding capacity and antioxidant ability,while shorten the fermention time.As referring to FY and PY,the water-holding capacity of PY was stronger than FY,and there were no significant difference in the fermentation time,microbial content,total sugar and flavonoids.While the sensory score of PY was lower than FY as a result of the sedimentation of asparagus powder,which needed to be further improved by adding suspension agent.2.Extraction of pectin from Akebia trifoliata peel and comparative analysis of its quality:there are a large amount of pectinin the Akebia trifoliata peel,and compared the Akebia trifoliate pectin through acid extraction?HCP?and hot water extraction?HOP?with the commercial apple pectin?AP?.Its result showed that the total sugar,reducing sugar and galacturonic acid content of HCP,as well as the water holding capacity and emulsifying capacity were all higher than HOP.HOP and HCP are darker than AP,but the contents of total sugar,reducing sugar,galacturonic acid and polyphenols are higher than AP,and the water-holding capacity,emulsifying ability and emulsifying stability are also better than AP.Therefore,the performance of HCP is better than that of HOP and AP.On this basis,the extraction process of pectin by acid method was optimized,and the optimal extraction process of pectin was obtained as follows:the pH of the extraction was adjusted to 2.0 by hydrochloric acid,the solid-liquid ratio of 1:30?g/ml?was set,and the extraction rate reached9.70%at 85?for 90min.3.Effect of Akebia Trifoliata pectin on the quality of yogurt:this study discussed the effects of different amounts of Akebia Trifoliata pectin on the quality of low-fat yogurt.Its results showed that the amount of lactobacillus and streptococcus thermophilus,total sugar and reducing sugar content,DPPH free radical clearance rate in low-fat yogurt increased with the amount of pectin,while the fermention time was reduced.When the amount of pectin reached 0.14%,DPPH clearance rate increased significantly.When the amount of pectin was0.14-0.22%,the firmness of yogurt was higher.When the amount of pectin was 0.18-0.22%,the sensory score was the highest;when the amount of pectin was 0.22%,the water holding and adhesiveness of yogurt were the highest.Combined with the experimental results,the addition of 0.22%of Akebia Trifioliata pectin could improve the water holding capacity and texture characteristics,thus enhance the sensory score of low-fat yogurt,increase the number of microorganisms,and shorten the fermentation time.4.Effect of Akebia Trifiliata pectin in combination with calcium on the quality of asparagus yogurt:preliminary experiments showed that different doses of HCP could not improve the sedimentatio of asparagus.In this study,at the base of adding asparagus powder with 0.22%HCP,and different doses of CaCl₂ were added to investigate the quality of yogurt.Its results showed that CaCl₂ of 0.075%could significantly shorten the fermentation time,increase water retention,and distribute asparagus powder in yogurt system,so as to improve the sensory score.6.Comprehensive comparison of the effects of pectin,calcium and asparagus powder on the storage quality of yogurt:this experiment compared the quality of low-fat yogurt?Con?,pectin yogurt?P?,pectin calcium yogurt?PCa?,pectin calcium mixed with superfine asparagus powder?PCaS?and pectin calcium mixed with conmmon asparagus powder yogurts?PCaC?during the 20d storage period at 4?.With the extension of the storage period,the pH,water retention,viscosity and other indicators of the five groups of yogurt showed a decreasing trend,and the acidity and whey precipitation rate showed an increasing trend,while the total phenol,lactobacillus and streptococcus thermophilus increased first and then decreased.Among the three stages,lactobacillus,streptococcus thermophilus,water retention,total sugar,reducing sugar,total phenol,particle size,fracturability and firmness of PCaS and PCaC groups were the highest,followed by P and PCa,and Con was the lowest.What's more,the sensory score of group PCaS was the highest,P and PCa were the second,and the PCaC group had a lower score close to Con due to the sedimentationof asparagus powder.It showed that the combination of pectin and calcium with seperfine asparagus powder could improve the sedimentation of asparagus,increase the number of lactobacillus and streptococcus thermophilus in yogurt,as well as the content of total sugar,reducing sugar and total phenol,and enhance the water retention,thus improve the sensory score and health value of low-fat yogurt.In contrast,the addition of Akebia trifiliata pectin and asparagus powder could shorten the fermenton time of low-fat yoghurt,improve the quality of low-fat yogurt,enhance its nutritional value and antioxidant capacity,enrich types of yogurt,and expand the application of the asparagus and the peel of Akebia Trifiliata.