Study On Separation,Identification And Control On Mould Contaminated Bacteria From Dried Persimmon

Dried persimmon is the main processing product of persimmon.It ‘s taste is sweet,and has rich nutrition and high healthcare value.Dried persimmon has high sugar and water,thus it is easy is contaminated by microorganism in processing and storage process,and even has mould.This processing way seriously affects the quality of dried persimmon and product exports.Studying the mold pollution features of dried persimmon and practical control technology can improve the product quality and shelf life dried persimmon,expand exports,promote persimmon processing.In this paper,the main mold pollution bacteria were isolated from mildewed dried persimmon and identified by morphology,ITS molecular biology molecular analysis.The effects of temperature,humidity and pH on the growth were also investigated and determined the thermal death point and time.Using physical and chemical methods of strain growth inhibition,and explore the inhibitory effect of ultraviolet irradiation treatment on finished product dried persimmon mildew.The main results and conclusions were as follows:1.Separation and identification of mold in mildewed dried persimmon: Two dominant fungi strains were isolated from mildewed dried persimmon,named S1 and S2.It has been verified to penicillium and aspergillus respectively by morphological features.The homology of two isolated strains reached to 99% Penicillium chrysogenum and Aspergillus niger by ITS rDNA molecular analysis and phylogenetic tree analysis.Eventually S1 and S2 were identified as Penicillium chrysogenum and Aspergillus niger.2.Bacterial characteristics of Main mold contamination in dried persimmon bacteria S1 and S2: Mould S1 Penicillium chrysogenum and S2 Aspergillus niger have roughly growth characteristic.The optimal growth conditions for strain S1 is as follows: temperature is 28?,humidity is more than 70%,pH is 6.0,the thermal death point and time is 60?,15 min or 65?,1 min;The optimal growth conditions for strains of S2: temperature is 30?,humidity is more than 70%,pH is 5.0,the thermal death point and time is 65?,15 min or 70?,1 min.3.The bacteriostatic ring was determinated by the using of food preservatives chlorine dioxide,sodium benzoate,potassium sorbate and double sodium for mould S1 and S2,and it is known that they have inhibitory effect,and the effect of chlorine dioxide is better than other preservatives.From the point of bacteriostatic effect,when the chlorine dioxide production is 30 ppm and 10 min for mould S1,the bacteriostasis rate is 99%,thus,the chlorine dioxide could reach better bacteriostatic effect in low concentration and a relatively short time.As well,when the chlorine dioxide production is 30 ppm and 15 min for mould S2 aspergillus Niger,the bacteriostasis rate is 90%,and when the chlorine dioxide production is 50 ppm and 15 min,the bacteriostasis rate is 99%.In a word,the chlorine dioxide has more effective to inhibit the growth of Penicillium chrysogenum.Through the studying the ultraviolet sterilization of strains S1,S2,when the irradiation time is for 10 min,the sterilization rate of mould S1 reached 93.85%,thus,the inhibition effect is good;and sterilization rate of S2 is 76.65% for the irradiation time is 10 min,thus,the inhibitory effect is relatively weak,In a word,UV can be used in practical production.4.The studying of the ultraviolet sterilization to dried persimmon products indicated ultraviolet treatment can effectively inhibit the growth of mold when processing time is 10 min storaged in room temperature within 10d;And UV treatment can increase the holding water of dried persimmon,and extend the shelf life of dried persimmon at room temperature.