Development On Compound Yogurt Of Tartary Buckwheat And It’s Quality Analysis

Buckwheat rice, buckwheat sprouts and black rice were used as the main raw material fordeveloping yogurt in this study. Through the determination of its dynamic changes of biomass,total flavonoids (TF), rutin (R), quercetin (Q) content and antioxidant capacity (DPPH andABTS radical scavenging ability), the optimal sampling time of buckwheat sprouts weredetermined. Then the buckwheat rice, buckwheat sprouts, black rice pulp and skimmilk wereprepared for yogurt, further determine the best yogurt production process and productionformula, finally go on with the yogurt quality analysis. The main results are as follows:1. A extraction and a analysis method for the determination of main flavonoids wereestablished. The results showed that the best extraction condition were determined as follows:extracting temperature50℃, extracting time25min, methanol concentration70%, ultrasonicfrequency50kHz. The reverse high performance liquid chromatography (RP-HPLC) wereused for the determination of flavonoids.2. Kinetic Studies of buckwheat sprouts were established. The results showed that thelength, FW and DWwere reached maximum value on day11. The total flavonoids and rutincontent increased steadily during the first eleven days. The highest content was obtained onday11, and its maximum value were51.50and47.96mg/g. The DPPH and ABTS radicalscavenging capabilities had the same change trend with total flavonoids, and its maximumvalue were477.63and215.24umol Trolox/g DW.3. The determination of the best yogurt production process and production formula.Buckwheat rice, buckwheat sprouts, black rice, and skim milk were used as the main rawmaterial, and through mixing, filtering, homogeneous, sterilization, fermentation and coldstorage process, we got the yogurt product.3.1. Processing conditions of raw materials. First the buckwheat rice pulp were got asfollows: buckwheat rice were fried at100℃for6min, and then the soaking condition weredetermined as follows: soaking temperature55℃, soaking time2h, ratio of solid to liquid1:5. The streaming time was7min, and the grinding ratio of solid to liquid was1:8, the pulpwere through100mesh. The buckwheat sprout slurry were got as follows: The streaming timewas10min, and the grinding ratio of solid to liquid was1:6, the pulp were through100mesh.Finally the buckwheat sprout pulp were got as follows: the soaking condition weredetermined as follows: soaking temperature25℃, soaking time1.5h, and the ratio of solidto liquid1:12, curing time was11min, and the grinding ratio of solid to liquid was1:8, thepulp were through100mesh.3.2. The formula of three kinds of yogurt: the optimal formula of sample1was obtainedby the ratio of buckwheat rice pulp to skim milk were40:60; The optimal formula of sample2 was obtained by using20%buckwheat rice pulp,15%buckwheat sprout slurry and60%skimmilk. The optimal formula of sample3was obtained by using15%buckwheat rice pulp,10%buckwheat sprout slurry,10%black rice pulp and60%skim milk.3.3. The choice of sweetener and stabilizer: the best sweetener was combination of4%xylitol and0.015%aspartame. The optimal stabilizer was combination of0.2%guar gum,0.3%CMC-Na.3.4. Determination of fermentation condition: through the changes of texture and pH, Igot the optimal fermentation conditions were got as follows: the fermentation temperature42℃, inoculation quantity3%and fermentation time4h.4. The quality analysis of yogurt.4.1. The physical and chemical indicators analysis: the fat content in the samples were1.2,1.0,1.6g/100g, the protein content in the samples were3.20,3.70,2.80g/100g, thevalue of pH and acidity were4.65,4.59,4.54and80.1,75.0,74.5°T, respectively. They wereall extremely significant differences(p <0.01). The samples showed no significant differencein the content of total amino acid content, the value were2.3764,2.4154,2.3589%respectively.4.2. The content of flavonoids: the content of total flavonoids, rutin, quercetin were allhave the same trend, the content of sample2was higher that that of sample1, and the contentof sample1was higher than that of sample3. The results showed that the adding ofbuckwheat sprout has a positive effect for the nutrition of yogurt.4.3. Aromatic compounds analysis: the volatile aromatic components in yogurt wereextractd by solid-phase micro-extraction(SPME) and were analyzed by GC/MS. The resultsshowed that the main aromatic compounds in the yogurts are acids, alcohols, aldehydes,ketones, hydrocarbons. The components in sample3is more dispersed and balanced. So theadd of black rice in the yogurt have a good coordination and equilibrium effect.4.4. The total number of lactic acid bacteria analysis: the number of lactic acid bacteriain the samples are all greater than1×10~6cfu/mL. The results reached the regulation of GB4789.35-2010which called “food microbiological analysis: lactic acid bacteria test”.4.5. The antioxidant activity analysis: the DPPH and ABTS radical scavenging capacitywere all have the same trend, the content of sample2was higher that that of sample1, and thecontent of sample1was higher than that of sample3. The results showed that the antioxidantcapacity of samples are related to its content of flavonoids.