Effect Of Dissolved Oxygen On The Quality Of NFC Orange Juice During Processing And Storage

China is one of the major countries for citrus planting and production.The annual output of citrus has been increasing year by year.As one of the main processed products of citrus,orange juice enjoys great popularity because of its fresh and sweet flavor.At present,consumers have increasingly higher requirements of dietary structure and nutrition.Not From Concentrate(NFC)orange juice has been proposed.However,browning,nutrient loss and aroma dissipation in the processing and storage of orange juice seriously restricts the development of the NFC orange juice industry.Among them,oxygen is one of the most important factors.At present,there is little research on the influence of dissolved oxygen(DO)on the quality of NFC orange juice during processing and storage.Therefore,we used NFC orange juice as the research object in this study.The color,soluble solids,Vc,total phenols,total flavones,5-hydroxymethyl furfural(5-HMF),rutin,hesperidin,citronellin,ferulic acid,caffeic acid and p-coumaric acid were used as indexes to explore the effect of"dissolved oxygen-temperature"on orange juice quality during the process of degassing and storage.The main research contents and conclusions are summed up as follows:1.Degassing is one of the important units in the processing of NFC orange juice.The orange juice samples were degassed to different DO contents at different temperatures(10?,20?and 30?,simulate room temperature in different seasons),and the effects of DO content on the nutritional quality of orange juice at different degassing temperatures were studied.The results showed that in 30°C,when the DO content increased from 0.3 mg·L^-1 to 7.5 mg·L^-1 at 30°C,the contents of Vc,total phenol and total flavonoids decreased by 21%,8%and 12%respectively.The contents of TSS decreased slightly.The reduction of rutin,ferulic acid,caffeic acid and p-coumaric acid were 41%,37%,23%and 19%respectively.When DO content was higher than 1.5 mg·L^-1,the(?)E value of the orange juice sample was greater than 1.5,which means an extremely significant difference from the control group(P<0.01).Compared with 30?,the DO content at 20?degassing had a smaller effect on the quality of orange juice.When the DO content at 10?was 0.3 mg·L^-1,there was no significant effect on the quality of orange juice.Therefore,the degassing temperature was 10?or lower,and the DO content in orange juice was removed below 0.3 mg·L^-1,which helps to obtain higher quality NFC orange juice.2.In order to explore the effect of DO content change in different oxygen-permeable packages on the low-temperature storage quality of NFC orange juice,glass bottles(BL),polypropylene(Polypropylene,PP)plastic bottles,polyethylene(PE)cooking bags(oxygen permeability:BL<PP<PE)were used to control the DO content in orange juice to varying degrees,ang avoid light refrigerate(4?).The results showed that the content of reducing substances,titratable acid(TA),rutin,hesperidin,and melanoside in all orange juice samples did not have a significant correlation with the oxygen permeability of the package.Sensory evaluation,the degradation rate of?E,Vc and total phenol,the formation of A₄₂₀ and 5-HMF were all significantly correlated with the oxygen permeability of the package(P<0.01).The DO content in BL packaging was the lowest,followed by PP packaging,and the DO content in PE packaging was the highest.The smaller the oxygen permeability of the package,the lower the DO content in orange juice,the more effectively it could slow down the deterioration rate of orange juice.When BL packaged orange juice was stored under refrigeration for 180 days,the DO content was always maintained at about 0.5 mg·L^-1,the value of?E was always less than 2,the value of A₄₂₀ remained basically stable,and the content of 5-HMF only increased by 0.076 mg·L^-1.And the degradation rate of Vc was only 9%,which was conformed as the first-level degradation kinetic model.In this case,and the acceptable time was 3 times the shelf life of refrigerated NFC orange juice on the market,which effectively extended the shelf life of NFC orange juice.3.At three selected storage temperatures of 4?,25?and 40?,BL and PP packaging materials were used to set a comparative study on the effects of DO content on the quality of NFC orange juice.The results showed that"temperature-dissolved oxygen-orange juice deterioration"was highly correlated.As the storage temperature increased,the content of DO in PP packaging varied.While the DO content in the BL packaging was maintained at 0.5 mg·L^-1 and below.The total flavonoid content of TSS and TA did not change as the temperature increased,and the microbial content was still within the range of national standards.The higher the storage temperature of orange juice in PP packaging,the faster the degradation rate of Vc and characteristic functional components(rutin,hesperidin,ferulic acid,caffeic acid and p-coumaric acid)(P<0.01),the Maillard reaction accelerated.The color difference?E of orange juice,the content of reducing sugar,the amount of 5-HMF produced and the value of A₄₂₀ increase rapidly.And the quality of orange juice underwent a degradation in a short time.The deterioration rate of orange juice in BL was slower than that in PP.The quality of orange juice in BL packaging stored at 4?was the best,and the acceptable time for sensory evaluation of quality was up to 180 days.The?E value in BL packaging at 25?was 3.11±0.070.The Vc content was reduced by 13%.The value of the browning index A₄₂₀ remained basically stable.The acceptable time for sensory evaluation of quality was 60 d,which was 4 times that of PP packaged orange juice at the same temperature,This was equivalent to the shelf life of commercial refrigerated NFC orange juice.These results indicated that reducing the DO content can extend the shelf life of NFC orange juice effectively even at room temperature.