Abstract
Food quality improvements of fresh fruits targeting both food preservation and human health is essential to advance healthy dietary options and to mitigate imbalanced nutrition-linked non-communicable chronic disease (NCDs) challenges globally. Specifically, protective phenolic bioactives of fruits with dual functional benefits can be harnessed to advance innovations for improving nutritional quality and post-harvest shelf-life of perishable fruits. Based on this rationale the dual functional benefits of plant phenolics were harnessed using novel biological elicitation strategies to modulate phenolic bioactive-linked protective responses in apple during storage in two interrelated studies. Bioprocessed food-grade elicitors [water soluble chitosan oligosaccharide -(COS) and phenolic enriched oregano extracts-(OX)] were targeted as post-harvest dipping treatments (2 & 4 g/ L) and compared with diphenylamine (DPA) (1 & 2 g/L) to enhance phenolic-linked antioxidant and anti-diabetic (type 2 diabetes) relevant properties of Cortland apple during 3 months of storage (4°C). The selection of bio-elicitors and respective doses were based on the foundations of the previous related study, which resulted in reduction of superficial scald of Cortland apple during storage. Apples sampled over 3 months as aqueous and ethanol (12%) extracts of peel and pulp were analyzed separately for total soluble phenolic content, phenolic profile, antioxidant activity, and glucose metabolism relevant α-amylase and α-glucosidase enzyme inhibitory activities using in vitro assay models. Enhanced soluble phenolic content and associated antioxidant activity were observed in ethanol (12%) extracts of apple peel with 4 g/L COS elicitor treatments after 2 and 3 months of storage. High chlorogenic acid and quercetin derivatives were found in peel extracts of Cortland apple, while pulp extracts had high chlorogenic and gallic acids. Additionally, high α-glucosidase enzyme inhibitory activity, which is relevant for managing post-prandial hyperglycemia of type 2 diabetes was also observed in bio-elicited apple peel and pulp extracts. Therefore, results of these two interrelated studies indicate that bioprocessed food grade elicitor such as OX and COS can be recruited as a novel tool to enhance protective phenolic responses for improving type 2 diabetes targeted food quality and post-harvest storage quality of apple.
Highlights
Increasing awareness among consumers about the beneficial impact of balanced nutrition and diet on human health is driving the demand and market value of fresh fruits and vegetables globally (Porat et al, 2018)
Similar level of soluble phenolic content was observed in stored apple peel and pulp (Adyanthaya et al, 2009, 2010; Barbosa et al, 2012)
Statistically significant differences in soluble phenolic content between apple sample (S), extraction solvent (E), elicitor treatments (T), storage duration (D) and their respective 2-way (S × E; S × T; E × T; D × S; D × E; D × T), 3-way (S × E × T; D × S × E; D × S × T; D × E × T), and 4way (D × S × E × T) interactions were observed at all post-harvest storage time points (Supplementary Appendix 1; Figures 2A,B)
Summary
Increasing awareness among consumers about the beneficial impact of balanced nutrition and diet on human health is driving the demand and market value of fresh fruits and vegetables globally (Porat et al, 2018). Previous studies indicated that higher consumption of apple is inversely related to reduced risks of several NCDs, such as cardiovascular diseases, asthma and pulmonary function, type 2 diabetes, inhibition of lipid oxidation, and potentially provides protection against certain types of cancers (Schiavano et al, 2015; Hodgson et al, 2016; Bondonno et al, 2017; Hua et al, 2018; de Oliveira Raphaelli et al, 2019) Some of these NCD preventative properties of apples are attributed to the composition and higher concentration of phenolic bioactives, like flavonoids and phenolic acids, which are naturally present and widely distributed in apple peel and pulp (Barbosa et al, 2012; Rana and Bhushan, 2016; Jakobek et al, 2020). Phenolic bioactive linked food quality improvements of apple can be targeted for dual functional benefits of enhancing human health protective functional properties as well as preservation qualities
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