Microemulsion based coatings with calcium and antioxidant for reducing chilling injury of ananas comosus

Abstract

Ananas comosus generally known as pineapple is one of Malaysia’s commodity and commercially cultivated across various region in Malaysia. A high-quality pineapple is valued from both its internal and external quality attributes. The standard postharvest practice and storage by refrigeration is recommended for perishable commodities which includes pineapple. However, cold storage causes physical and chemical deterioration known as chilling injury (CI). Although certain pineapple cultivar had been genetically developed with resistance toward CI, the findings of this study showed that CI affected quality attributes of all cultivars tested i.e. Morris (Queen), Josapine (hybrid of Spanish and Smooth Cayeen) and MD-2(hybrid of Smooth Cayeen), regardless of their genetic makeup. Therefore, thisresearch aims to develop a stable and edible microemulsion loaded with calciumchloride and clove essential oil which objectively to minimize the CI and maintain thequality attributes of pineapple both chemically and physically. An optimizedmicroemulsion formulation with particle size of 203.22 nm, zeta potential (?- potential)of +3.65 mV and emulsion stability index (ESI) of 24.1 was obtained by applying0.01% w/w whey protein isolate, 0.13% w/w carboxymethyl cellulose at pH 4.96. Thisoptimized condition and formulation was obtained via response surface methodology.Characterization of optimum microemulsion was conducted morphologically andphysically, and a stable microemulsion was observed for 30 days in response of sizeparticle, ?-potential and ESI. In overall, microemulsion coating performance resultssuggest that this coating significantly improved most of the quality attributes,antioxidant activity and storage capacity of the pineapples up to 30 days of storage at4 ± 2 °C. Coated pineapples sustained up to 21 days with minimum effects of CI ascompared to control which only capable to tolerate up to 7 days. A significant decreasein calcium content was found based on soluble calcium content and stained calciumlocalization qualitatively proven the occurrence of CI. The orthogonal testing tosupport this finding was by GC-MS primary metabolite analysis, in which coatedpineapple showed greater shifts in metabolism by presence of distinctive amino acidsand significant higher level of organic acids, soluble sugar and soluble alcohol asindicator of response to chilling stress and adaptive mechanisms.