Mathematical Modeling Pseudomonas Spp.Growth And Microflora Composition Variation On Agaricus Bisporus Fruiting Bodies During Chilled Storage

Agaricus bisporus is the most widely cultivated and most productive edible fungus in the world.Postharvest browning of A.bisporus fruiting bodies(ABFB)occurs easily,and would lose their commercial value within a few days if without refrigeration,leading to nutrient loss,moisture loss,textural changes,and microbial growth.Especially,ABFB could be an ideal medium for the growth of pathogenic and spoilage bacteria.Therefore,in this paper fresh ABFB were used as material,a comprehensive analysis of the dynamic changes of the surface microbial community and the dominant spoilage bacteria of fresh-keeping ABFB under 4? storage.Secondly,study the growth of background microflora and dominant spoilage bacteria on the surface of ABFB under different temperature conditions,and establish an effective microbial growth prediction model.Finally,combined with the quality indicators of ABFB,the effects of ?-polylysine hydrochloride(?-PL)on the growth of ABFB surface background microflora and dominant spoilage bacteria were research,and a shelf life prediction model was establish.Then the prediction model developed in this study can be used to evaluate the growth behavior of spoilage bacteria on ABFB and assess ABFB shelf-life.The main conclusions were as follows.1.Traditional plate culture and the 16 S r DNA high-throughput sequencing were used to investigated and analyzed the bacterialcomposition in the surface of fresh ABFB from different sources.The results showed that 53 bacterial species from 4 phyla and 36 genera were isolated and identified from two samples ABFB by the traditional plate culture method.Using 16 S r DNA high-throughput sequencing method,a total of 30 phyla and 773 genera of bacteria were identified from A sample fruiting bodies,and a total of 8 phyla and 156 genera of bacteria were identified from B sample fruiting bodies,which indicated the species was diversity.During the storage and preservation of fresh ABFB,the bacterial species richness decreased and the total colony increased as the storage time prolonged.The results showed that Pseudomonas spp.was the most abundant genus of ABFB during storage and preservation at 4?.In addition,4 strains of Pseudomonas spp.were isolated and identified through traditional plate culture methods,which were P.fluorescens,P.migulae,P.tolaasii,and P.agarici.Therefore,Pseudomonas spp.became the dominant spoilage bacterium.2.Under the condition of 4? ? 32?,the growth curve of background microflora and Pseudomonas spp.On the surface of ABFB included three characteristic phases: lag phase,logarithmic growth phase and stable phase.Three primary models(Huang,Baranyi,and Reparameterized Gompertz model)were compared to evaluate the effect of temperature on bacterial growth.The Reparameterized Gompertz model was a better fit than the Huang and Baranyi models to describe thegrowth of background microflora and Pseudomonas spp..Three secondary models(Huang square-root,Ratkowsky square-root,and Arrhenius-type model)were compared to further evaluate the effect of temperature on bacterial growth.The results show that the Huang square-root model has better fitting accuracy,and its predicted minimum growth temperature of Pseudomonas spp.was-0.717?,which is closer to reality.Therefore,the Huang square-root model was more suitable for describing the effect of temperature on growth of background microflora and Pseudomonas spp.on ABFB.3.The growth of background microflora and Pseudomonas spp.on ABFB was inhibited by ?-Polylysine hydrochloride(?-PL).The inhibition models of different concentrations ?-PL of on background microflora and Pseudomonas spp.were established at 4?,16? and 25?,respectively.The results showed that only at 4?,?-PL could inhibit the growth of Pseudomonas spp.on the surface of ABFB,but had no obvious effect on the growth of the background microflora on the surface of ABFB.Moreover,there was also no significant difference in sensory quality,L* value,hardness,moisture content and weight loss rate between ABFB samples treated with different concentrations of ?-PL(P>0.05).This showed that ?-PL treatment had no obvious effect on the preservation of ABFB,but also has no side effects.