Extending the shelf life of guava fruits using silver nanoparticles infused biopolymer coatings

Abstract: Guava is a climacteric fruit with a short shelf life (5-8 days). The rapid postharvest deterioration of guava fruits poses a major challenge in increasing longevity and retaining quality. This study examined the impact of silver nanoparticles (AgNPs) infused into different biopolymer edible coatings, including beeswax, gelatin, guar gum, and xanthan gum, to extend the shelf life which is relatively unexplored in guava fruits. The results revealed that AgNPs-coated fruits exhibited significantly prolonged shelf life: beeswax-coated fruits lasted 11 days, gelatin-coated fruits lasted 9.5 days, guar gum-coated fruits lasted 7 days and xanthan gum-coated fruits lasted 6.25 days, compared to the control (4.25 days). The highest PLW (Physiological Loss in Weight) of 70.44 % was noticed in uncoated fruits and the lowest PLW of 38.73 % in beeswax + AgNPs at the 12^th day of storage was noticed. The highest firmness of 24.25 kg cm^-2 was observed in beeswax + AgNPs and the lowest firmness of 6.00 kg cm^-2 was noted in uncoated fruits on the 12^th day of storage. The highest Total Soluble Solids (TSS) content of 16.80° Brix on the 10^th day was recorded in the control (uncoated fruits), but the fruits shrunk and lost consumer acceptance. On the contrary, the lowest value of 11.80° Brix was found in fruits coated with beeswax + AgNPs, but there was only a slight decline on 10^th day. The fruits retained their form and shape. High vitamin C retention was observed in beeswax + AgNPs coating as 195.2 mg100g^-1, but a massive reduction was observed in control as 169.6 mg100g^-1 on the 12^th day of observation. The observations taken on the 12th day of storage denote delayed starch conversion with a high percentage of total sugar reduction at 5.51 in beeswax + AgNPs coating. The high percentage of total sugars was observed in control as 9.22. The biopolymer coatings with AgNPs delayed fruit senescence and maintained better physiological and biochemical properties, demonstrating their potential as an effective postharvest treatment for guava fruits. This is the first study of its kind in guava using AgNPs with biopolymers. The results of the study were highly promising, opening the door for more intensive research and the need to scale up this technique to address postharvest loss of guava fruits.