Study On The Juice Processing Suitability And Stability Of Different Types Of Citrus

Citrus is one of the largest yield fruits in the world with high nutritional value.China is a big producer of citrus and has various varieties.But most citrus is mainly fresh food,and the variety suitable for juice production is not only low proportion,relatively simple,low juice yield and poor nutritional quality.These factors also limited the development of China's citrus processing industry,resulting in unsalable citrus and other problems.As a new type of juice emerging in recent years,NFC citrus juice can retain the flavor and nutrition of citrus to the greatest extent,but there is a problem of easy stratification,which also affects the acceptance of consumers and the market value of fruit juice.Therefore,the key to improve the quality of NFC juice and develop the processing industry is to choose the appropriate processing varieties,optimize the processing technology,explore the mechanism of its stability,and improve the stability of NFC citrus juice.In this study,twenty different varieties of citrus were used as the raw material to study their juice processing adaptability,optimize the processing technology suitable for the production of NFC citrus juice,and explore the effect mechanism of the operation unit(high-pressure homogenization,HPH)on the stability of NFC citrus juice,which will provide reference and theoretical basis for the production of high-quality NFC citrus juice.The main research contents and results include the following aspects:1.Analysis on adaptability of different citrus varieties to juice processing.Sensory characters and physicochemical properties of 20 citrus varieties were measured and analyzed,and the suitable or suitable citrus varieties were selected by percentage evaluation analysis method.The results showed that 20 different citrus varieties could all be used as raw materials for juice processing.Among them,the comprehensive scores of Nanfeng mandarin and' Wei zhang'Satsuma orange of citrus reticulata blanco,long-leaf orange,Sunkist navel orange,yuanfeng navel orange,tarocco blood orange,' Bei Bei 447' jinchen orange,Gannan navel orange,Newhall navel orange,Valencia orange,Bingtang orange,Hamlin orange and zigui navel orange of orange,'murcott' of miscellaneous citrus and Wendan pomelo of pomelo were all above 80,making them the excellent varieties for NFC citrus juice processing.Duncan grapefruit had the lowest comprehensive score because of its high acidity,but it could be mixed with high sugar varieties to improve the utilization of resources.2.Optimization of NFC citrus juice processing technology.Through single factor test,solid acid ratio and pulp settlement rate were taken as indexes.Orthogonal tests were used to optimize the processing technology based on the comprehensive score of NFC citrus juice.The optimized process is as follows: pectin addition 0.075%,homogenization pressure 100 MPa,sterilization time 11 min,sterilization temperature 85?,shear rate 7500 rpm,and shear time 5 min.When the above process is used to make juice,the comprehensive score of NFC citrus juice reaches 90.45 points,with good comprehensive quality.In addition,it was found that high pressure homogenization had the most significant effect on the stability of NFC citrus juice.3.The influence mechanism of high-pressure homogenization(HPH)on the stability of NFC citrus(orange)juice was preliminarily studied.NFC orange juice was treated with different HPH parameters and its pectin structure and stability indexes were measured.The effects of HPH on the structure of pectin and the turbidity stability of NFC orange juice and their correlation were studied.The results showed that HPH could change the structure of pectin in NFC orange juice and improve its stability.Increased stability of NFC orange juice can improve the sensory and nutritional properties of the juice.With the increase of homogenization pressure and passes,HPH increased the galacturonic acid(Gal A)content and the linearity of pectin,while decreasing the molecular weight(Mw),pectin branching,and rhamnogalacturonan(RG)contribution.At the same time,it was found by SEM that cracks and pores of different sizes formed on the surface of pectin,implying depolymerization.In addition,HPH treatment improved the turbidity of orange juice,reduced the particle size,and inhibited the sedimentation of the particles.Although the activity of pectin-methylesterase(PME)in NFC orange juice after HPH treatment was still at a high level,the turbidity stability of NFC orange juice was improved.This was because the homogenized pectin was easier to interact with the particles in orange juice,thus effectively improved the stability of NFC citrus juice.Correlation analysis showed that the stability index of NFC orange juice was closely related to the structure and properties of pectin,which indicated that pectin directly or indirectly affected the stability and sensory quality of orange juice.In summary,the adaptability of 20 different varieties of citrus to juice processing was analyzed,the processing technology of NFC citrus juice was optimized,the effects of operation units(high-pressure homogenization)on the stability of NFC citrus juice and pectin structure were explored,and the correlation between the increase in the stability of NFC orange juice and pectin structure was clarified,which would provide theoretical guidance for the production of highquality NFC citrus juice.