| Fresh-cut yam is fresh,convenient and rich in essential amino acids,diosgenin,vitamins,allantoin and other functional ingredients.Although the market demand was large,the freshcut yam often browning during storage.In addition to be browning,it was found that fresh-cut yam would turn yellow when stored at specific conditions.In our study,the formation conditions of the yellowing fresh-cut yam were studied and the quality of it was evaluated;the structure and composition of yellow pigment（YP）were revealed;the stability and biological function of YP were clarified.The experimental results are as follows:（1）To determine the best condition of yellowing fresh-cut yam and evaluate its quality.Storage temperature,gas composition and cutting thickness affect the yellowing of fresh-cut yam.The best yellowing conditions were: 25 ℃ storage,0.1 cm thickness,80% N2 with 20% O2 modified atmosphere packaging（MAP）,storage time was 18 h.There were no significant difference in hardness,soluble solids,total phenol content,sensory evaluation and smell,between the yellowing fresh-cut yam and the no yellowing fresh-cut yam except for the color change,which indicated that there was no significant difference in the quality of them（2）The structure and composition of YP were analyzed.The YP was separated,purified and identified by ultra-high liquid chromatography-mass spectrometry（HPLC）.It was found that the TP was mainly composed of three yellow substances,with the largest proportion being bisdemethoxycurcumin（BDMC）（73.7%）.The formula of the other two substances were C19H18O3（19.2%） and C19H16O3（7.1%）.（3）The stability of YP was revealed.The results indicated that the YP had high thermal stability,when the temperature was over 123 ℃,the effect of thermal degradation was obvious.The thermal stability of it was higher than that of anthocyanin,chlorophyll,lycopene and other natural pigments.The simulated gastrointestinal digestive system indicated that the degradation of the YP would be happen after gastrointestinal digestion,and the degradation rate after intestinal digestion was significantly higher than that after gastric digestion by about 30.6 times.Gastric degradation rate of YP was lower than anthocyanin,while the intestinal degradation rate of it was higher than anthocyanin.The YP has light instability,which was easy to degrade under the LED light of different light sources.The order of degradation effect from high to low was blue light,red light,white light and green lightl,and its degradation process accords with the first-order degradation kinetics.（4）To clarify the function of YP in antioxidation and protection of DNA from oxidative damage.The binding pattern between YP and ct DNA was studied by UV-vis,fluorescence,viscosity and ionic strength.The results showed that the YP and ct DNA first attracted each other by static electricity,and then combined by intercalation.The YP prevented the group of ct DNA from oxidative damage.Key words: Fresh-cut Yam YP Ingredients Properties. |
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