Effect Of EVOH Composites Packaging On Rice Storage Quality And Screening Of Broad - Spectrum Antagonistic Bacteria Of Dominant Bacteria In Rice

Rice is one of the main grain varieties of daily life, with the accelerated development of urbanization, the increasing miniaturization offemily and the quickening pace of life, the market share of small packaging rice is increasing, but during storage, quality deterioration often cause a great waste of food. Studies have shown that the main source of rice quality deterioration in storage, sales and consumption process lies in the change of rice moisture content, rice itself respiratory metabolism and microbial decomposition, and these were all related to rice packaging materials, packaging mode and storage environment. This paper chose common PEP composite materials and barrier higher EVOH composites for rice small packaging, and stored rice in high temperature rapid aging and low temperature environment, and compared the changes of different varieties of rice quality. Meanwhile, on the basis of the analysis in the physical and chemical quality, the surface microbial growth dynamic and the eating quality of rice, this paper was studied from the perspective of biological perspective point of view, using the antagonistic effect of Pseudomonas bacteria on rice surface predominant bacteria, screened the suitable Pseudomonas for the production of biological preservative, and providing the basis for latter use in rice storage preservatioa The main results are as follows:(1) Fresh rice Changyou No.5 was vacuum packed and non-vacuum packed by PEP and EVOH under high temperature rapid aging, dynamic changes of the moisture content of rice, fatty acid, reducing sugar and microbial quantity were tested to determine the effects of two packing materials and two packing modes. The results showed that vacuum treatment is more conducive to maintaining rice moisture than non-vacuum treatment, and can inhibit the formation of rice fatty acid and reducing sugar in the early stage, and the mold and bacteria growth on the rice surface have different degrees of inhibition. Compared with PEP materials, EVOH material have stronger barrier ability to moisture and gas, and can keep rice moisture and slow down the formation of sugar and fatty acid to a certain extent, meanwhile, Strong barrier EVOH inhibited mold growth on rice surface, but also provided favorable conditions for facultative anaerobic bacteria growth. Compared with PEP material, rice packing with EVOH material had worse taste quality, large, shiny, aroma, taste and other indicators of rice packaging with EVOH declined lager, and obviously in later storage. This could be seen that the growth of facultative anaerobic bacteria on rice surface has a greater impact on rice eating quality.(2) Fresh rice Changyou No.5 was vacuum packed and non-vacuum packed by PEP and EVOH under tow humidity conditions at a relative humidity of 50%and 80%, tested and analyzed dynamic changes of the moisture content of rice, fatty acid, reducing sugar and microbial quantity. The results showed that rice packaging with two kinds of material under relative humidity of 80% conductive to the accumulation of fatty acids and sugar in early storage, different relative humidity on rice reduction sugar and fatty acid content had no significant effect in later storage. The high relative humidity of the storage environment for mold growth on EVOH materials packaging rice surface and bacterial growth on PEP materal packaging rice surface has certain inhibitory effect, and significantly contributed to decrease rice taste value with EVOH packaging material, it showed that higher relative humidity environment was not conductive to hold rice eating quality. The results were similar as rapid aging, compared with the PEP material, EVOH material have dominant physical and chemical properties, and can effectively inhibit the growth of mold on rice surface under low temperature, but for bacterial growth. On eating quality, EVOH material packaging rice taste worse than PEP material, taste, viscosity, flavor and appearance declined significantly.(3) 90 strains of Pseudomonas isolated from fresh rice surface and rhizosphere soil was used for confrontation treadmill test on 3 strains of dominant fungi and 3 strains of dominant bacteria isolated from the rice surface, screened 7 strains of Pseudomonas with broad-spectrum antagonism, bacterial universal primers were used to amplify the 7 strains of Pseudomonas bacteria DNA, and the amplified products were sequenced to obtain the molecular strain classification information. The results showed that about 14.4% of the 90 strains of Pseudomonas antagonistic the main advantage of the mold on rice surface, and about 37.8% of Pseudomonas antagonistic the dominant bacteria, of which there were seven strains have obvious broad-spectrum antibacterial activity on the surface of the rice bacterial and fungal. By comparison respectively the sequencing results were highest similarity to Pseudomonasputida, Pseudomonas chlororaphis, Pseudomonas fluorescens, Pseudomonas sp. and so on. These strains have broad-spectrum antagonistic and provide strain resources for further research and development of biological antistaling agent for rice.