| Propionic acid and its salts are effective and inexpensive mold inhibitors,and even more effective than sorbic acid and formic acid.Propionic acid and its salts are not only easy to handle and use but also have no corrosive.In this thesis,Nanguo pear was soaked in 1.0 g/L sodium propionate(SP)solution to study the inhibitory effect on the the fruit pathogenic fungus,Penicillium expansum and the Nanguo pear fruit ripening.The main results are as follows:(1)Different concentrations of SP(1.0,2.0,3.0 g/L)significantly inhibited mycelial growth and spore germination of P.expansum in vitro and had concentration-dependent.It was not obvious that the inhibitory effect of SP treatment on the diameter expansion of Nanguo pear fruit inoculated P.expansum;1.0 g/L SP treatment significantly reduced the incidence of fruit inoculated with P.expansum comparing with the control.(2)SP treatment significantly improved the activity of polygalacturonase(PG),pectin methylesterase(PME),cellulose(Cx)andβ-glucosidase(β-glu)in Nanguo pear fruit during room temperature storage,accelerated the decomposition of propectin,resulting in significant increase in soluble pectin content,and declined cellulose and hemicellulose content.The result of atomic force microscope image showed that the soluble pectin treated with SP degradated quickly the structure was looser than the control.(3)Compared with control,SP treatment significantly accelerated the release of ethylene,enhanced respiratory intensity,promoted indistinctively decrease of flesh firmness,total chlorophyll,ascorbic acid,titratable acid content,and increase of weight loss in Nanguo pear fruit.The soluble solids content and reducing sugar content remained the same trend that SP treatment was higher than the control in 0-6 d,and was lower in 9-18 d.Meanwhile,SP treatment inclined the a~*value,declined the b~*value,and maintained the L~*value in the chromatic aberration,and therefore accelerated the yellowing of Nanguo pear fruit.In summary,postharvest SP treatment had certain inhibitory effect on the growth of P.expansum,but could not effectively control the occurrence of postharvest blue mold in Nanguo pear fruit;Postharvest SP treatment had certain ripening effect on Nanguo pear fruit,and did not reduce the fruit quality.Therefore,SP can be used as a ripening agent for fruits and vegetables. |
