Effects of a chitosan coating on the post-storage quality of plum fruit

Abstract

The effects of a chitosan coating on the quality and storability of 'Stanley' plum fruit were investigated. Plum fruits were treated with a 1.0 % w/v chitosan coating and stored at 1 ± 1 °C under 90–95% relative humidity for 28 days, and, subsequently, held at 24 °C for four days to evaluate shelf life. Some basic physical and chemical quality indices (weight loss, fruit firmness, soluble solids content, pH, content of total sugars, inverted sugars, sucrose and acids) were evaluated after storage, and after four days of shelf life. Furthermore, the occurrence of pathogens in treated and control fruit was monitored. Weight loss was pronounced after cold storage and it almost doubled during shelf life in both groups of plums, and the results obtained show that the chitosan coating could not prevent shrivelling. Although, the chitosan-coated fruits showed higher firmness after cold storage and during shelf life (2.51 kg/cm2, and 1.75 kg/cm2, respectively) than the control fruits (2.28 kg/cm2, and 1.66 kg/cm2, respectively), the observed differences were not statistically significant. There was also no significant difference in chemical composition between treated and control fruits. However, the percentage of fruit infected with Monilinia spp. at the end of cold storage was slightly lower in the chitosan-coated fruit (2.00%) than in the untreated fruit (3.33%). The effectiveness of chitosan coating in maintaining plum quality during storage therefore remains questionable.

Raziskali smo vpliv prevleke iz hitozana na kakovost in sposobnost skladiščenja plodov sliv sorte 'Stanley'. Plodove sliv smo obdelali z 1,0 % m/v prevleko iz hitozana jih skladiščili pri 1 ± 1 °C pri 90–95 % relativni vlažnosti 28 dni, nato pa jih hranili pri 24 °C štiri dni, da bi ocenili rok uporabnosti. Nekatere osnovne fizikalno-kemijske kazalnike kakovosti (izguba mase, čvrstost plodov, vsebnost topne suhe snovi, pH, vsebnost skupnih sladkorjev, invertnih sladkorjev, saharoze in organskih kislin) smo izmerili po skladiščenju in po štirih dneh shranjevanja pri sobni temperaturi. Nadalje smo spremljali pojav patogenov pri tretiranih in kontrolnih plodovih. Izguba mase je bila po hladnem skladiščenju izrazita in se je med shranjevanjem pri sobni temperaturi pri obeh skupinah sliv skoraj podvojila, dobljeni rezultati pa kažejo, da obloga iz hitozana ni preprečila zgubanosti kožice. Čeprav so plodovi,prevlečeni s hitozanom, pokazali večjo trdoto po hladnem skladiščenju in med rokom trajanja (2,51 kg/cm2 oziroma 1,75 kg/cm2) kot kontrolni plodovi (2,28 kg/cm2 oziroma 1,66 kg/cm2), opažene razlike niso bile statistično značilne. Prav tako ni bilo pomembne razlike v kemični sestavi med tretiranimi in kontrolnimi plodovi. Vendar pa je odstotek plodov, okuženih z Monilinia spp. ob koncu skladiščenja nekoliko manjši pri plodovih, obloženih s hitozanom (2,00 %) kot pri netretiranih plodovih (3,33 %). Učinkovitost premaza s hitozanom pri ohranjanju kakovosti sliv med skladiščenjem ostaja torej vprašljiva.