| Fresh noodles with fruits and vegetables could make up for the lack of vitamins,minerals and other essential nutrients in traditional noodles,which is popular with consumers.Among them,fresh spinach noodles with green color and high nutritional value occupy a large market share in fruit and vegetable noodles.However,due to the high content of bacterial,phenols,and chlorophyll,the shelf life of fresh spinach noodles is very short and it could gradually turn yellow and dark during storage,which decreases consumers'purchasing desire.Therefore,this article focused on the effects of moderate hydrothermal treatment(MHT),tea polyphenols combined with MHT,and acidity regulators on the color,microorganism,and quality of fresh spinach noodles,in order to provide solutions for extending the shelf life of fresh spinach noodles.Firstly,the effects of MHT on the color,microorganisms and quality of fresh spinach noodles were investigated.The results showed that MHT at higher temperature could reduce significantly(35)E*(0-24h)and PPO activity of fresh spinach noodles.When the treatment temperature was 80?,the relative humidity was 90%,and the treatment time was 5 min,the(35)E*(0-24h)and PPO activity of fresh spinach noodles were 4.61 and 27.50 U·g-1·min-1,respectively(The(35)E*(0-24h)and PPO activity in the control group were 11.73 and 326.82 U·g-1·min-1,respectively).The retention rates of chlorophyll and carotenoid in fresh spinach noodles was higher than 89%in the 80? treatment group,and there was no significant change in the content of free phenol(P>0.05).The mold and yeast count of fresh spinach noodles after 80? treatment was lower than 10 CFU/g and the initial total plate count decreased significantly(P<0.05).The hardness and chewiness of fresh spinach noodles were increased significantly by MHT.In addition,the reduction of free sulfhydryl content(from 3.64?mol/g to 1.65?mol/g)and starch gelatinization enthalpy(from 5.49 J/g to 4.77 J/g)as well as the microstructure results indicated that the protein structure aggregation and starch partial gelatinization occurred in fresh spinach noodles when treated at 80?,90%,5 min.Secondly,the effects of tea polyphenols combined with MHT on the color and quality of fresh spinach noodles under light conditions was investigated.MHT combined with tea polyphenols inhibited significantly(P<0.05)the browning of fresh spinach noodles under light conditions.When the addition of tea polyphenols was 0.05%,the(35)E*(0-24h)of fresh spinach noodles was only 9.73(13.53 in the control group).And when the addition of tea polyphenols was 0.075%,the retention rates of total chlorophyll and carotenoids of fresh spinach noodles after 24 h storage were 80.38%and 86.32%,respectively(67.09%and 65.77%in the control group).In addition,0.1%tea polyphenols increased significantly the tensile force of fresh spinach noodles(P<0.05),but had no significant effect on the chewiness and hardness of noodles(P>0.05).Furthermore,the effects of acidity regulators(sodium carbonate,potassium carbonate,and citric acid)on the microorganism,color,and quality of fresh spinach noodles were investigated.0.11%citric acid(p H 5.22),0.3%sodium carbonate(p H 9.17)and 0.4%potassium carbonate(p H 9.31)could inhibit the growth and reproduction of bacteria during storage of fresh spinach noodles.Adding sodium carbonate and potassium carbonate could reduce significantly(P<0.05)the?E*(0-24h)of fresh spinach noodles.When the addition of sodium carbonate and potassium carbonate were 0.15%and 0.4%,respectively,the?E*(0-24h)of fresh spinach noodles decreased to 11.88 and 11.89(14.56 in the control group).All three acidity regulators inhibited fresh spinach noodles PPO activity and their inhibitory effect has occurred in noodle making.The results of chlorophyll content showed that when the addition of potassium carbonate and sodium carbonate were 0.21%and 0.3%,respectively,the highest total chlorophyll content of fresh spinach noodles after 24 h storage was 137.66mg/g and 135.47mg/g,respectively(121.39mg/g in the control group).The addition of sodium carbonate and potassium carbonate increased the hardness,chewiness and tensile strength of fresh spinach noodles,while citric acid had the opposite effect.Finally,the effects of the optimal conditions of MHT(80?,70%,3 min),the optimal addition of potassium carbonate(0.21%),the combination of MHT with potassium carbonate and common preservatives on the color,microorganism and quality of fresh spinach noodles were investigated.The results showed that the shelf life of fresh spinach noodles could be extended to more than 69 days after MHT.On the 69th day,the(35)E*(0-24h)of the experimental group was ranged from 10.28 to 10.84(21.35 in the control group).In addition,the texture quality of fresh spinach noodles kept better during storage under the optimal preservation conditions.In conclusion,MHT combined with potassium carbonate could prolong significantly the shelf life of fresh spinach noodles and delay the browning of noodles during storage. |
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