Isolation And Inhibination Of Spoilage Moulds In Spicy Gluten Snack And Study On The Antifungal Way Of ?-Polylysine

Spicy gluten snack(SGS)is a kind of spicy food,its main raw material is flour,which was extrused by extruding-expansion machine and then combined with oil and seasonings.Because of its attractive flavor,it is quite popular in China.However,moulds are easy to live in it under specific conditions.In order to inhibit the growth of mould,in this paper,we aimed to work out a formula and research the antifungal way of?-polylysine(?-PL).The main conclusions of this paper are listed as follows:Four kinds of moulds were isolated and purified from the spoiled SGS.They were Aspergillus flavus,Penicillium patulum,Aspergillus albicans and Aspergillus versicolor.The total bacterial counts(TBC)were determined in the raw material of SGS.The result was that TBC in oil pickled pepper were much more than seasoning powder and half-finished SGS,up to 1.0 × 106 CFU/g and 3.5×103 CFU/g.After separating and purifying,six kinds of moulds were found in oil pickled pepper.The four kinds of spoiled moulds were all in it.Five kinds of moulds existed in seasoning powder,containing Aspergillus flavus and Asperillus versicolor.This result suggested that mould's growth in SGS was intimately related to the microorganism in raw materials.The growth of moulds is also closely related to water activity(Aw).To the bacteria,when the Aw of SGS was 0.74,the TBC kept falling down to 290 CFU/g in 30 days.However,when the Aw were 0.82 and 0.78,the numbers were failed at the very start and ended up rising.To the mould,mould was found in SGS(Aw 0.74)at 27 days.But,for the 0.78 and 0.82 of SGS,the times were 18 days and 9 days.This result shows that the Aw is lower,bacteria and mould are more unsuited for growing in it.Refer to GB2760-2014,preservatives were selected.The result showed that natamycin,?-PL and sodium dehydroacetate could form an obvious bacteriostatic ring to the four kinds of moulds.It demonstrated the three kinds of preservatives could inhibit the four kinds of moulds.The minimal inhibitory concentration(MIC)and minimal fungicidal concentration(MFC)experiments indicated Aspergillus flavus had the strongest resistance to preservatives.The inhibitional effects of the preservatives to the Aspergillus flavus mycelium were determinded by the mycelia growth inhibition method.They all showed great inhibitional effect to the mycelium.Taking inhibitional rate of mycelium as index,the optimized inhibitor complex was determinted by Box-Behnken response surface design.They were 10 mg/kg natamycin,140 mg/kg ?-PL and 250 mg/kg sodium dehydroacetate.The result showed they did not show a synergic action.The inhibitional rate was 71.05%after 24 h treated with the optimized inhibitor complex.The inhibitional rates were all 100%to the other three species of moulds after 6 days.Using this optimal rate in the SGS(Aw 0.78),bacteria and mould were controlled in experimental group,while they were thrived in control group.The growth of Aspergillus flavus was inhibited by ?-PL through observing the germination of Aspergillus flavus conidia and measuring the electric conductivity.Because of the cell rupture,the mould was died.?-PL owns strong positive charge,it can damage the organelles,cause the leakage of cytoplasm and the loss of cell formal function.TEM sesults also could prove it.Germination of Aspergillus flavus spores could be affected by ?-PL within 12 h,750 mg/kg ?-PL could completely inhibit the germination of spores.By measuring the electrical conductivity and absorbance values to reflect the permeability of cell membrane,the experiments showed that?-PL could destroy the mold's cell,increased the permeability,and the contents flowed out.Aspergillus flavus mycelium was observed by optical microscopy and SEM,the mycelium of experimental group was very plump,smooth,had uniform diameter.Howerer,the surface of mycelium treated with 1500 mg/kg ?-PL was not smooth.From TEM results,the intracellular organelles evenly distributed,had a clear structure in the control group.Mitochondrion was round and full,internal ridge structure was clear.Contents were not flowed out.The cavity area expanded treated with 1500 mg/kg ?-PL.Nucleus,mitochondria and other organelles were not visible.Antufungal way of ?-PL can be analyzed:?-PL is adsorbed on membrane via electrostatic action and increases cell's permeability,and then ?-PL enter the cell,combined with organelles membrane,cell rupture,the contents flows out,mould compeletely die.