| Plums are extensively cultivated,produce high yields,and are rich in nutrients,but there is very little plum commodity industry.In addition,plums are concentrated in the hot summer.During the process of picking,transportation,storage,fresh marketing,and processing,the plums can sustain damage due to mechanical processes,pests,and diseases.The fruit is especially susceptible to contamination by pathogenic fungal microorganisms,which causes decay and deterioration,significantly reducing the storage period of the fruit.This study uses plums selected from five main cultivated Sichuan varieties.The compositional differences between the plum varieties are examined to determine which fruit is more suitable for consuming fresh and which should be processed.The plums more suited for fresh consumption require storage and preservation.The impact of different antibacterial agents on spoilage bacteria is examined,while the effect of combining these antimicrobial elements with 1-methylcyclopropene(1-MCP)and modified atmosphere packaging(MAP)on the quality of the plums during storage is explored.This provides the experimental foundation for the processing and storage of the plums.(1)Five types of plums(Prunus salicina cv.“Qingcuili,” “Cuihongli,” “Yinhongli,”“Xiguali,” and “Fengtangli”)were selected as raw materials,while the compositions of the different fruits were determined,analyzed,and compared.The results showed variations in the nutritional content of the different plum varieties.“Xiguali” displayed the highest single fruit weight,water content,ash content,titratable acid,total phenols,total flavonoids,and anthocyanins.The fruit was softer with a lower sugar and acid content.It was suitable for making plum juice,fruit wine,fruit vinegar,and other fermented products.“Cuihongli” and“Yinhongli” displayed the highest sugar-acid ratio and sweeter fruits,which are suitable for fresh consumption.“Qingcuili” exhibited the highest polyphenol oxidase level and was most easily oxidized,increasing the processing difficulty.“Fengtangli” fruits were soft and bright in color with low moisture content and were suitable for processing and producing preserved fruits.(2)As research objects,the plums(Prunus salicina cv.“Qingcuili,” “Yinhongli,” and“Cuihongli”)were suitable for fresh consumption,while the corruption bacteria Prunus chinensis was identified and purified.Furthermore,the antimicrobial sensitivity of sodium dehydroacetate,ε-polylysine,and natamycin(NT)to putrogenic bacteria was examined.According to the results,seven strains were isolated from the three plum types,namely Pichia occidentalis,Pichia kluvier,Pichia tericola,Candida,Saturnispora diversa,Saccharomycopsis crataegensis,and Saccharomyces cerevisiae.The three antibacterial agents exhibited an inhibitory effect on these seven strains,of which the impact of NT was superior.NT treatment at 0.4 mg/m L effectively inhibited all seven yeast strains.No significant differences were evident between the antibacterial effect of sodium dehydroacetate and ε-polylysine.Of the seven yeast types,Pichia occidentalis showed the highest tolerance to sodium dehydroacetate and ε-polylysine,which displayed a distinct antibacterial effect at concentrations of 0.1 g/m L and 0.06 g/m L.Pseudosporomyces displayed the highest tolerance to NT up to a concentration of 0.4 mg/m L,after which it started to produce a noticeable antibacterial effect.The varying sensitivity of the different strains to various antibacterial agents may be related to differences in the strain cell structures.It may also be associated with the effect of different antibacterial agents on the substructures,enzymes,cell walls,and cell membranes of the respective strains.(3)This study compared the effect of untreated and polypropylene(PP)box packaging with that of 1-MCP combined with NT and MAP on the quality of the plums at storage temperatures of 4 ℃ and 25 ℃.The combination of MAP and NT effectively reduced the incidence of decay during storage,which was extended to 21 d at 25 °C and 120 d at 4 °C.MAP treatment significantly decreased the weight loss rate(P<0.05),which did not exceed 5% during storage.Moreover,1-MCP treatment reduced peak respiration while decreasing and impeding the peak soluble solids(TSS),hindering the fruit metabolism rate.NT+1-MCP+MAP and 1-MCP+NT+MAP maintained low pectin methylesterase(PME)activity during storage,effectively restricting an increase in water-soluble pectin and a decrease in raw pectin,maintaining a high level of hardness.Additionally,the 1-MCP+MAP treatment effectively maintained peroxidase(POD)activity,delaying an increase in the malondialdehyde(MDA)content.Therefore,the antioxidant activity of the plums was improved,the oxidative damage during storage was reduced,fruit senescence was delayed,and the storage period of the fruits was prolonged.Consequently,NT+1-MCP+MAP and 1-MCP+NT+MAP could most effectively guarantee the quality of the plums during storage. |
PDF Full Text Request