Effects of cutting shapes and thicknesses on the quality of minimally processed pineapple (Ananas comosus), cv. 'Queen Victoria'

Abstract

Cutting shape and size are physical factors that influence the keeping quality of minimally processed fruits and vegetables. Since these factors have not been studied as determinants of the keeping quality of minimally processed pineapples (MPP) cv. ‘Queen Victoria’, this study was conducted. A 2 x 2 factorial treatment structure laid on a randomized block design (RBD) was used. The treatments, which were blocked by days, were combinations of two cutting shapes (slices and chunks) and two thicknesses (5 mm and 10 mm). Pineapples of 25 - 50% ripeness were minimally processed to give rise to the treatments, which were then vacuum-packed at 47.5 kPa in laminated Low Density Polyethylene (LDPE) vacuum bags and stored at 4 ± 1⁰C for 12 days. Quality changes were evaluated at three-day intervals over a storage period of 12 days. Translucency score was evaluated by comparison method against standard colour charts. Electrical conductivity of leachate (ECL), firmness and pH were measured instrumentally. Ascorbic acid (AA) content was determined by titration with dichlorophenolindophenol (DCPIP) dye. Yeasts and moulds counts (YMC) were also enumerated using the classical standard method. Data were analysed using analysis of variance (ANOVA), and sum of squares due to treatment were split into main effect cutting shape, main effect thickness and interaction effect. All the keeping quality attributes of the MPP were significantly affected by storage time (p<0.001). Cutting shape also significantly affected translucency score (p<0.01), firmness (p<0.01) and YMC (p<0.01). Slices were firmer and had the lowest translucency score and minimized fungal growth as opposed to chunks. No significant interaction effect (p>0.05) was observed between cutting shapes and thicknesses on translucency score, firmness and YMC of the MPP. However, a significant interaction effect was noted between these two variables on ECL (p<0.05) and AA content (p<0.001). A thickness of 10 mm exhibited lower translucency score, higher ECL, reduced firmness and lower AA losses. pH was not significantly affected (p>0.05) by cutting shapes and thicknesses. Ten-mm slices maintained all the above-stated quality parameters, except ECL and pH, when stored at 4 ± 1⁰C for 12 days.