| Hot chain distribution is the main distribution method of collective nutritious meals.It is required to maintain the center temperature of the dishes above 60℃before the meal is prepared and delivered to consumers,so that the color,aroma and taste of the dishes can be better maintained in a short period of time.The purpose of this article is to study the changing laws of the various qualities of vegetable dishes in the cooking process and the storage of the hot chain in nutritional catering,and to provide basic data for the standard construction and key technologies of the entire hot chain distribution system.(1)Six common vegetable dishes were the research objects,including leafy vegetables,root vegetables,melons and fruits,and cauliflower which were explored the changes in their nutritional and sensory qualities at four hot chain storage temperatures of 55℃,60℃,65℃and 70℃after three hours.The experiment found that as the storage temperature of the hot chain increased,the moisture content,ascorbic acid content,carotenoid content and total phenol content in the six vegetable dishes all lost to varying degrees.The higher the temperature,the faster the loss rate.The hardness of various types of vegetables during storage at different temperatures showed a decreasing trend.Among them,the hardness of Chinese flowering cabbage dishes changed the most.The appearance and color of pumpkin,carrot and lotus root dishes did not change significantly after three hours of storage at the four different temperature heat chains,and they could still maintain a good appearance.However,the appearance of broccoli and Chinese flowering cabbage dishes after three hours of storage at70℃in the hot chain was severely yellowed,and lost the bright color after conventional cooking,and the sensory scores were significantly reduced.(2)Taking Chinese flowering cabbage dishes as the research object,explored the changes of sensory quality at 55℃,60℃and 65℃storage temperature.Establish a regression curve model to predict the quality change of the hot chain preservation process.The Pearson correlation analysis of each index and sensory score under the hot chain preservation of Chinese flowering cabbage dishes was carried out,and the a~*value was determined as the evaluation index of the shelflife model of Chinese flowering cabbage dishes under the hot chain distribution.According to the coefficient of determination R~2,the Logistic equation was selected for data fitting.The R~2values at the storage temperatures of 55℃,60℃and 65℃were 0.997,0.988 and 0.987,indicating that the prediction model fits well.The relative errors of the predicted and true values of the three hot chain temperature preservation conditions were 1.43%,6.81%and 8.01%.It could quickly and conveniently predict the remaining shelf life of Chinese flowering cabbage dishes under hot chain preservation conditions.(3)Taking the classic green leafy dish Chinese flowering cabbage dishes as the research object,and explored the four cooking methods of steaming,blanching,oil stir-fry and microwave,and the changes in the quality of Chinese flowering cabbage dishes during the preservation process at 65℃.The results showed that the ascorbic acid retention rate of oil-fried cabbage dishes treated with hot chain preservation at 65℃for two hours was the lowest,which was 76.64%,and the appearance was deteriorated and yellowing was serious.After hot chain preservation,the ascorbic acid retention rate of blanching Chinese flowering cabbage dishes was 87.72%.The appearance was complete,bright green,and the total sensory score was the highest.Comprehensive consideration was given to selecting blanching as the best cooking method under hot chain preservation conditions.After determining the optimal cooking method under the heat chain preservation conditions of Chinese flowering cabbage dishes,five different blanching times of 40 s,60 s,90 s,120 s,and 150 s were explored on the quality changes of Chinese flowering cabbage dishes during the heat chain preservation process including the effects of soluble protein,total glucosinolates,total phenols,total flavonoids,nitrite and the total number of colonies.With the increase of time,the contents of soluble protein,total glucosinolates,total phenols,and total flavonoids all showed a significant decreasing trend during the hot chain preservation at 65℃,and the longer the blanching time,the higher the loss rate.Among them,short-term blanching in 40 s and 60 s could increased its nutrient retention rate.However,blanching for 40 s cannot completely kill microorganisms and enzymes in vegetables.The sterilization effect was lower than that of long-term blanching.The total number of colonies and nitrite content would increase significantly in the middle of the hot chain preservation(P<0.05),but all were within the scope allowed by Chinese standards.(4)The process conditions for the effective preservation of green and crispiness of Chinese cabbage dishes under 65℃hot-chain storage were explored.Through single factor experiment and Box-Behnken response surface method,the comprehensive weighted score of Chinese cabbage dishes was optimized,and the regression model was obtained as follows:Y=49.8445+17.4387A+0.7447B-6.416C+1.5427D-0.2918AB+4.9608AC-0.03502AD+0.0992BC-0.02159BD+0.1517CD-10.1784A~2+9.688E-003B~2-1.8734C~2-0.01625D~2.The best process conditions were:the concentration of calcium chloride in the soaking solution was0.94‰,the ultrasonic soaking was 24.75 min,the concentration of sodium bicarbonate in the blanching solution was 1.84‰,and the blanching time was 40.08 s.Under this model,the comprehensive weighted scoring was 91.98,and the relative error with the predicted value of93.94 was 2.08%,which proved that the model was feasible.Compared with the untreated group,the hardness of the stems of the cabbage dishes treated with the optimal process conditions was significantly improved during the 4 hours storage at 65°C in the hot chain(P<0.05).It could maintain a good appearance,and moderate in hardness,crisp and tender.It was proved that the optimal process condition of green protection and brittleness is effective and feasible and has practical application value. |
