Post harvest storage stability of kinnow mandarin through applications of silver nanoparticles based coatings

Abstract

Influence of carboxy methyl cellulose (CMC) and guar gum based silver nanoparticles containing coatings was studied on the postharvest storage stability of kinnow mandarin (Citrus reticulata cv. Blanco) stored at 4 oC and 10 oC (85-95% relative humidity) for a period of 120 days. Physicochemical qualities, microbiological evaluations, quantities of three major aroma compounds (limonene, linalool, γ-terpinene) and sensory attributes were monitored after every 15 days of storage. Microbiological quality was assessed by monitoring the principal spoilage microbes (yeast and moulds, psychrotrophic bacteria, E. coli, Salmonella and Staphylococcus aureus). Sensory evaluation was carried out using 9 point hedonic scale by a panel of 25 experienced penalists for peel colour, flesh colour, juice colour, fruit texture, fruit taste, fruit flavour and overall acceptability. Overall, the results revealed an increase in peel pitting, total soluble solids (TSS), total sugars, reducing sugars, non-reducing sugars, pH and weight loss in the fruits, but this increase was comparatively less significant in coated fruits stored at 4 oC. Ascorbic acid, total phenolics and antioxidant activity were significantly enhanced in coated fruits stored at 4 oC. Titratable acidity was significantly decreased during storage except for coated kinnow stored at 4 oC. In control samples stored at 10 oC, a high intensity of fruit rotting and no chilling injury was observed. Total aerobic psychrotrophic bacteria, and yeast and moulds were noticed in all treatments during storage, but the growth was not significant in coated fruits at 4 oC. Staphylococcus aureus was not noticed in coated fruits stored at 4 oC, while E. coli and Salmonella were not found in any treatment during storage. Limonene, linalool and γ-terpinene concentrations were significantly reduced during storage in uncoated, and those kinnows coated and stored at 10 oC. However, the storage did not alter the qualitative aroma profile of kinnow. Hedonic scores of sensory evaluation panel appeared to correlate well with the aroma profile and manifested the GC-MS results. Based on the present study, the quality of kinnow fruit can be kept good for 4 months, when stored at 4 oC and for 2 months at 10 oC.