| Mulberry,the mature fruit of the mulberry tree,is rich in anthocyanin,non-anthocyanin phenolic substances,polysaccharides and other functional components.Mulberry pomace(MP),a by-product of the production of mulberry juice,contains even higher contents of anthocyanins,non-anthocyanin phenolic substances and other components than of the whole mulberry fruit.It can be speculated that MP may be a good component for the development of functional food,but it has not been well utilized yet.In this study,it was used in the development of functional flavored yogurt products,and its effects on the physicochemical properties and texture of flavored yogurt products were studied.The details are as follows:1.The effect of mulberry pomace powder on the quality of stirred yogurtIn this experiment,the mulberry pomace was dried by a heat pump and then pulverized into fine powder,and MP powder was added to stirred yogurt up to 3%(w/w)to prepare a functional flavored yogurt,and the effects of MP on physicochemical and structural properties of the products during refrigeration were investigated.It was found that during 28 days of refrigeration,MP powder brought a pink to dark red color to yogurt,decreased brightness(L*)and yellow-blue(b*)values,increased red-green(a*)values,and decreased p H,increased the contents of TA,TPC and TAC and the free radical scavenging activities of DPPH and ABTS in a dose-dependent manner.The consistency,viscosity,and viscosity index of the yogurt samples were significantly increased,and the firmness of the yogurt samples was reduced.The addition of MP powder significantly reduced the pore space and channels within the sample and improved the microstructure of functional yogurt.Interestingly,the TPC and TAC contents of MP-fortified yogurt increased continuously during 28 d of refrigeration.Three monomeric anthocyanins(C3G,C3 R and Pg3G)and six individual non-anthocyanidin phenolics(resveratrol,catechol,catechin,rutin,quercetin and quercetin)in MP were identified and quantitatively analyzed.Experiments show that MP can be used as a natural antioxidant to help improve the physicochemical and texture properties of yogurt,and has the potential as a natural stabilizer.2.The role of mulberry pomace polysaccharide(MPP)in regulating the quality of functional yogurt with mulberry pomace powder addedSince polysaccharide is one of the main components of MP,and polysaccharide has the effect of regulating the rheological and textural properties of liquid and semi-solid foods,it can be speculated that MPP should play an important role in the contribution of MP improving the quality of yogurt.0%(control),0.5%,1.0% and 1.5% MPP were added to reconstituted skim milk,respectively,and then fermented into yogurt samples to study their influences on physicochemical,textural properties and microstructure of yogurt samples stored at 4℃.characteristics.The addition of MPP had a significant effect on the color,p H,titratable acidity and antioxidant activity of yogurt samples in a dose-dependent manner.Different doses of MPP had different effects on the water holding capacity,rheology,texture and microstructure of yogurt.The addition of 0.5% MPP had the most significant effects in increasing the water holding capacity of yogurt,improving rheology,texture and microstructure.These results indicated that an appropriate amount of MPP can effectively improve the gel properties,physicochemical parameters,antioxidant capacity and microstructure of yogurt,and MPP is an important functional component for MP in improving the rheological and textural properties of yogurt.3.The role of mulberry pomace polyphenols in regulating the quality of functional yogurt with mulberry pomace powder addedOn the basis of finding that MP powder affects the physicochemical and textural properties of yogurt,the role of polyphenols,that is,mulberry pomace polyphenol-enriched extract(MPPE),is studied.MPPE was prepared with mulberry pomace powder as raw material,and added to the yogurt system at 0.50%,0.75%,1.00%and 1.25% before and after fermentation to produce MPPE-enhanced yogurt samplesstirred yogurt samples.The effects of MPPE on the physicochemical,lactic acid bacteria activity and textural properties of fortified yogurt stored at 4 ℃ were investigated.The results showed that the addition of MPPE deepened the color,decreased the hardness,consistency,viscosity and viscosity index,changed the microstructure,and significantly increased the antioxidant activity of flavored yogurt.Compared with the addition before fermentation,the addition of MPPE after fermentation significantly increased the angiotensin-converting enzyme inhibitory activity(ACE-I)and the activity of lactic acid bacteria,and decreased the synersis of yogurt.The higher the MPPE concentrations,the more significant the effects on each parameter.The experiments showed that polyphenols played an important role in MP in enhancing the antioxidant activity of yogurt and enhanced the ACE-I activity of yogurt.4.In vitro simulated digestion study of functional yogurt rich in mulberry pomace polyphenolsPolyphenol is an important functional component of MP and can interact with milk protein.Whether the mulberry polyphenol extract affects the digestion and absorption of nutritional functional components in yogurt products is not yet known.In this experiment,yogurt samples containing 0.50% MPPE were used to analyze the changes of polyphenol release and degradation,ACE-I activity and free radical scavenging activity in oral,gastric and intestinal digestion stages.The results showed that,polyphenols and anthocyanins decreased significantly during oral digestion,while antioxidant activity increased significantly;In vitro gastric digestion significantly improved the release and antioxidant activity of polyphenols and anthocyanins;however,during intestinal digestion,polyphenols,anthocyanins and antioxidant activities decreased significantly.These results suggest that MPPE enhanced the bioavailability and antioxidant bioactivity of in mulberry polyphenol-fortified yogurt,promoting intestinal absorption and health benefits of polyphenols.These findings help to elucidate the effects of MP on antioxidant capacity and polyphenol stability,and help design dairy products with better functional quality. |
