Quality preservation of walnut kernels using edible coatings

A L Grosso,V Nepote,N R Grosso,C M Asensio

doi:10.3989/gya.0350181

Abstract

The objective of this work was to evaluate the performance of various edible coatings for preserving the quality of walnut kernels (W) during storage. Three edible coatings based on carboxymethyl cellulose (CMC), methyl cellulose (MC) and whey protein isolates (WP) were prepared. Coated and uncoated walnuts (WC) were stored for 210 days at room temperature (23±2 °C). After 210 days, WC presented the highest peroxide value (PV = 3.06 meqO2/kg), conjugated dienes (CD = 3.01) and trienes (CT = 0.31), pentanal, nonanal, hexanal, and decane, 5,6-bis (2,2-dimethylpropylidene) contents. Meanwhile, WMC showed the lowest PV (1.20 meqO2/kg), CD (2.26) and CT (0.17) and the lowest decrease in carotenoid content (0.60 mg/kg). The L* value measured in walnut oil decreased in all samples. MC, CMC and WP coatings showed protection on walnuts against the deterioration process. MC coating displayed the best performance.

Highlights

The walnut (Juglans regia L.) is a crop of high economic importance for the food industry (Martínez et al, 2013)
In the later stages, it acts as a catalyst in oil oxidation (Moslehi et al, 2015)
WC experienced the highest increase in PV (3.06 meqO2/ kg). These results showed that the application of the Carboxymethyl cellulose (CMC), methyl cellulose (MC) and whey protein isolates (WP) coatings to walnut samples generated a protective effect on the product during the storage period

Summary

Introduction

The walnut (Juglans regia L.) is a crop of high economic importance for the food industry (Martínez et al, 2013). For this reason, the cultivated area is rapidly growing in many countries (Christopoulos and Tsantili, 2011). The lipid oxidation of walnuts results in losses of essential fatty acids and vitamins, the appearance of off-flavors, and the generation of toxic compounds and color changes which decrease their nutritional, sensory, chemical and economic value and limit the shelf-life of walnut kernels (Salcedo et al, 2010; Grosso et al, 2017)

Objectives

Methods

Results