Study On Coating Effect And Its Improvement Of Chitosan In Cherry Tomatoes

Cherry tomatoes are delicious and nutrient-rich. As a regional fruit and vegetable, their qualitychanges a lot and they are easy to cause postharvest losses leading to serious economic losses in thecourse of transportation and storage. Therefore it’s important to develop effective and safe fresh-keepingtechnology in order to reduce postharvest losses. The use of chitosan has received extensive attentionfor fruits and vegetables’ fresh-keeping due to its good film forming and antibacterial properties. But thesingle chitosan has poor coating and fresh-keeping effect, adding addition agent can solve such problemto a certain extent. Based on Qianxiμ cherry tomatoes as our research object, we investigate the coatingeffect of chitosan and other polysaccharides in order to replace addition agent added in chitosan coatingand develop safe and natural compound polysaccharide antistaling agent. The main contents and resultsin details are as follows:(1) The effect of EB irradiation on chitosan’s molecular weight and structure has been studied.Results showed that with the increasment of irradiation dose, chitosan’s molecular weight reduces andparticles size decreases gradually; In the range of5kGy to300kGy, electron beam irradiation has lesseffect on chitosan’s structure.(2) The effect of EB irradiation on chitosan’s antimicrobial effect and coating propertydemonstrated that above100kGy, chitosan has the best inhibition of spoilage organisms. With theincrease of irradiation doses, cherry tomatoes’ rotting rate is on the decline, among which the rottingrate of cherry tomatoes coated by chitosan irradiated by above100kGy is lower than controlsignificantly (P≤0.05). In addition, weight loss of cherry tomatoes coated by chitosan irradiated by EBat certain dose declines.(3) The effect of concentrations which were1%,2%,3%respectively on100kGy treatedchitosan’s antimicrobial effect and coating property demonstrated that with the increase of chitosan’sconcentrations, chitosan’s antimicrobial effect enhances. The rotting rate of cherry tomatoes increaseswith the increase of chitosan concentrations, but is higher than the control. Weight loss of2%chitosancoating is lower than that of1%and3%chitosan significantly (P≤0.05), but is higher than the control.(4) Results of addition agent Tween20and1,2-propanediol on chitosan’s fresh-keeping effect inwhich chitosan was irradiated by100kGy showed that adding addition agent can effectively solve theproblem of chitosan’s peeling up and reduce cherry tomatoes’ roting rate and weight loss significantly(P≤0.05), but has no significant effect on peel hardness, pulp hardness, Vc content, titratable acid andsoluble solids of cherry tomatoes (P＞0.05).(5) The antimicrobial effect and coating property of2%sodium alginate,1%xanthan gum and0.5%konjac powder were studied. Results showed that they all have no inhibition effect on yeast andmold (P＞0.05). Sodium alginate has a slight inhibition of bacteria and actinomycetes and konjacpowder a slight inhibition of actinomycetes, on the contrary xanthan gum promotes the growth ofbacteria and actinomyces. During the storage time, only konjac powder coating can reduce rotting rateand weight loss of cherry tomatoes significantly (P≤0.05). (6) The best volume ratio of chitosan whose weight-average molecular weight is about5.027×104at the EB dose of100kGy and konjac powder for cherry tomotoes fresh-keeping has been investigated.Results showed that when the volume ratio of chitosan and konjac powder is1to2, cherry tomatoeshave the lowest rotting rate and weight loss, at the same time it has no significant effect on peelhardness, pulp hardness, Vc content, titratable acid and soluble solids (P＞0.05).