Effect Of Processing Styles And Calcium Treatment On Quality And GABA Accumulatian Of Fresh-cut Broccoli Stems

Broccoli contains a variety of vitamins,minerals and dietary fiber,as well as polyphenols andγ-aminobutyric acid（γ-aminobutyric acid,GABA）and other antioxidant active substances.It is known as the"vegetable crown".It is a nutritious and healthy vegetable.The main edible part of broccoli is the flower bulb,which causes a lot of waste of broccoli stem and leaf resources and environmental pollution.Broccoli stems occupies a large proportion of broccoli plants,and after peeling,the taste is crisp and has high edible value.At the same time,the juice loss after cutting is less,which is conducive to fresh-cut processing.The main purpose of this article is to promote the synthesis and accumulation of GABA in fresh-cut broccoli stems under the premise of ensuring product commerciality and edible safety.This article discusses the effects of calcium chloride treatment and different processing methods on the quality and GABA content of fresh-cut broccoli stems and their mechanisms,which provide a basis for the development of fresh-cut broccoli stem products and the comprehensive utilization of broccoli by-products.The main findings are as follows:1.The effects of different cutting methods on the quality and GABA accumulation of fresh-cut broccoli stems during storage at 10℃for 48 h were explored.Fresh broccoli stems were cut into filaments,1/2 slices,and slices,with damage strengths of 12.5 cm²/g,5.7 cm²/g and 5.3 cm²/g,respectively.Studies have shown that the total number of colonies,weight loss rate and hardness of broccoli stems after cutting into filaments,1/2 slices and slices increased,and the content of chlorophyll and flavonoids decreased.The content of total phenol,DPPH free radical scavenging rate and GABA increased during the storage period,and the greater the mechanical damage intensity,the more obvious the content increase,reaching the highest values at 12 h.The results shown that there was no significant difference in quality between different cutting methods during the storage period,and they maintaind good commodity value.At the same time,fresh-cut treatment could significantly increase the synthesis and accumulation of phenolic substances and GABA,thereby improving the quality of fresh-cut broccoli stems.2.The effects of different concentrations（0,0.5,1.0,1.5 and 2.0%）of Ca Cl₂solution treatment on the quality index and GABA content of fresh-cut broccoli stems stored at10°C were studied.The results showed that the treatment of fresh-cut broccoli stems with an appropriate concentration of Ca Cl₂solution can effectively inhibit microbial growth,water loss and browning,and delay the decrease in hardness and chlorophyll content.In addition,calcium treatment further increased the accumulation of phenolic substances and GABA content and maintained the quality of fresh-cut broccoli stems.However,treatment with too high a concentration of calcium could not continue to increase the nutrient content.The study found that when the concentration of Ca Cl₂solution was 1.0%,the effect was the best,and the quality of fresh-cut broccoli stems was the highest.Treatment of fresh-cut broccoli stems with 1.0%Ca Cl₂solution could effectively promote the GABA metabolic pathway,increase the activities of GAD enzyme and GABA-T enzyme,thereby transforming glutamate to increase the synthesis and accumulation of GABA content.In the degradation pathway of polyamines,the content of polyamines such as putrescine,spermine and spermidine were increased to varying degrees by external mechanical damage stimulation and calcium treatment salt stress.At the same time,DAO enzyme and PAO enzyme,as the key enzymes of the polyamine degradation pathway,had a certain increase in their activity.AMADH enzyme converts the intermediate product generated by polyamine degradation into GABA,and the activity was also improved.3.The effects of different cooking treatments（steaming,microwave and blanching）on the nutrient content of fresh-cut broccoli stems treated with 1.0%Ca Cl₂and stored at 10℃for 12 h were studied.The results shown that different cooking methods had different effects on the GABA content and quality of broccoli stems.Both steaming treatment and microwave heating treatment increased the content of polyphenols and flavonoids in fresh-cut broccoli stalks and the antioxidant capacity such as DPPH free radical scavenging rate to maintain a higher GABA content and effectively maintain a higher quality.The boiling treatment caused the loss of various nutrients such as GABA,and the content was significantly reduced,and the antioxidant capacity such as the ABTS+free radical scavenging rate was significantly reduced.