Preparation Of Functional Indocalamus Leaves Tea Beverage With Rich Aroma By Enzymatic Method

With the improvement of living standards,people’s demand for soft drinks has increased from delicious and thirst-quenching to delicious and nutritious.Most of the soft drinks on the market today are produced with water,sweeteners,acidulants and stabilizers,etc.Numerous studies have shown that long-term intake of soft drinks containing these additives may affect human health.Therefore,in order to meet the new demand of consumers for natural,healthy and functional soft drink products,this study proposes to use two plant ingredients,glutinous rice and Indocalamus leaves,to increase the content of prebiotics in the product and enrich the aroma of the product by enzymatic method,and develop a natural and healthy drink.Firstly,an enzymatic preparation of a glutinous rice hydrolysate enriched with the prebiotic,Isomaltooligosaccharides(IMO),was carried out using an enzymatic method.In order to increase the IMO content in hydrolysate,the conditions of the liquefaction,saccharification and transglucoside processes were explored in this study.The optimal liquefaction process was to wash glutinous rice and soak it at room temperature for 3 h,then add high temperature resistantα-amylase at an addition rate of 100 U/g glutinous rice and liquefy it for 30 min at 90°C.For the saccharification and transglycosylation processes,this study firstly compared the saccharification effects of three different sources of saccharification enzymes,and the results showed that the enzymatic hydrolysis products of Biozyme LNC fungal α-amylase had higher maltose content(46.64 mg/m L)and lower glucose content(8.68 mg/m L),which was more suitable for the saccharification and transglycosylation processes.The way of saccharification and transglucosidation had a great influence on the yield of IMO.In this study,the effect of three different saccharification and transglucosidation methods on the yield of IMO was compared,and the results showed that the partial saccharification followed by transglycosylation process could produce more IMO(23.73%)in a shorter time(10 h).The orthogonal test optimized the glycosylation process as follows: glutinous rice was liquefied with water in the ratio of 1:8,then add fungal α-amylase to the liquefied solution at the addition rate of 41.25 U/g glutinous rice,saccharify at 55°C for 3 h,and then add α-glucosyltransferase at an addition rate of 493.50 U/g glutinous rice to continue to act for 14 h.The total yield of Isomaltose(IG2),panose(P)and Isomaltoriose(IG3)in the enzymatic solution of glutinous rice obtained under these conditions was25.32%.Secondly,the aroma of Indocalamus leaves(commonly known as dumpling leaves)extract was prepared.In order to better extract the active ingredients in Indocalamus leaves,the enzymatic method was used in this study.The results showed that β-glucosidase could improve the dissolution rate of the active ingredients and at the same time improve the aroma of Indocalamus leaves extract,while the effect of cellulase was not good.The data of GC/MS showed that the relative contents of alcohols,acids and ketones in Indocalamus leaves extract treated with β-glucosidase increased,especially the relative contents of linalool(120.65%),leaf alcohol(24.65%),benzyl alcohol(104.24%)and phenylethanol(254.95%),which contributed more to the aroma of Indocalamus leaves,increased by a larger amount.This indicates that β-glucosidase can hydrolyse the glycosidic aroma precursors in Indocalamus leaves,releasing volatile aroma substances to achieve the aroma enhancement effect of the extracts.This study further optimised the enzymatic process conditions for β-glucosidase.The most suitable process conditions were obtained as follows: Indocalamus leaf powder and water were mixed at a ratio of 1:10,and then β-glucosidase was added at an addition of80 U/g of Indocalamus leaf powder,and the enzymatic digestion was shaken at 55°C for 6 h.Kombucha is a health drink made from the fermentation of black tea bacteria.In order to reduce the glycemic index of the glutinous rice enzymatic solution and to obtain metabolites with beneficial effects,as well as to enrich the product ranges,this study selected Gluconacetobacter saccharivorans L4,a black tea bacterium with unique metabolic characteristics,and Kluyveromyces marxianus LBBE-2,a yeast with low alcohol production,to ferment the glutinous rice enzymatic solution to obtain the Indocalamus leaves kombucha beverage base containing metabolites such as gluconic acid and glucuronic acid with a mild sour flavour.The fermentation process was optimised as follows: Gluconacetobacter saccharivorans L4 and Kluyveromyces marxianus LBBE-2 were mixed at a ratio of 9:1,inoculated at 2%(v/v),and the fermentation was shaken at 30°C and 220r/min for 5 d.The amount of reduced residual sugar in the fermentation broth obtained under these conditions was 46.54 mg/m L,the content of acetic acid was 0.51 mg/m L,and the total acidity was3.12 g/L.Finally,in this study,the above obtained glutinous rice enzymatic solution and Indocalamus leaves kombucha beverage base were compounded with Indocalamus leaves extract to prepare Indocalamus leaves tea beverage and Indocalamus leaves kombucha beverage.When the blending ratio of glutinous rice enzymatic digestion solution and Indocalamus leaf extract was 7:3,the overall evaluation of the Indocalamus leaves tea beverage was better,and the main physicochemical indexes of the blended dumpling tea beverage products were: IG2,P and IG3 total content 20.39g/L,glucose 23.77 g/L,maltose 2.03 g/L,total sugar(calculated by glucose)728.38 g/L,reducing sugar(calculated by glucose)39.03 g/L,total flavonoids(calculated by rutin)0.04 g/L and soluble solids 6.69%.Since the fermented glutinous rice enzymatic solution was heavily acidic,it was diluted with pure water in the ratio of 1:4 before blending with Indocalamus leaf extract.The overall evaluation of Indocalamus leaves kombucha beverage was better when the blending ratio of glutinous rice fermentation dilution solution and Indocalamus leaf extract was 6:4.The main physicochemical indexes of the blended Indocalamus leaves kombucha beverage product were: IG2,P and IG3 total content 2.70 g/L,glucose 6.74 g/L,maltose 0.29 g/L,total sugar(calculated by glucose)101.44 g/L,reducing sugar(calculated by glucose)5.51 g/L,total acidity(calculated by acetic acid)0.48 g/L,total flavonoids(calculated by rutin)0.05 g/L and soluble solids 1.75%.