The objective of this work was to evaluate the performance of various antioxidants (ethyl acetate-soluble polyphenols: PAE; water-soluble polyphenols: PH; and butylated hydroxytoluene [BHT]) on the preservation of walnut oil (W) during storage. An oven test was conducted on the walnut oil samples: without antioxidants (control: WC) and with antioxidants: PAE (WPAE), PH (WPH), and BHT (WBHT) during a 16-day storage at 60 C temperature. Chemical parameters related to deterioration were analyzed during storage: peroxide value (PV), conjugated dienes (CD) and conjugated trienes (CT), and carotenoid content (CC). Volatile compounds were also analyzed. PV, CD, CT, and volatile compounds related to oxidation of lipids such as; nonanal, hexanal, butanal, and (E)-2-heptenal increased in all samples during storage. The increase of these variables was greater in WC and lower in WPAE and WPH. WPAE, WPH, and WBHT displayed a better preservation of volatile compounds that influence the walnut-characteristic flavor like D-limonene, and a lower increase of aldehydes and furans. The CC exhibited a decrease in all samples during storage. WPAE presented the greatest CC value along the storage and was followed by WPH. Antioxidants helped to preserve walnut oil against deterioration processes. PAE and PH displayed good antioxidant activity and in some cases showed a better performance for quality preservation of walnut oil compared to the BHT antioxidant.
The objective of this study was to evaluate the sensory stability of coated walnuts during storage. Four walnut samples were prepared: uncoated (NC), and samples coated with carboxymethyl cellulose (NCMC), methyl cellulose (NMC), or whey protein (NPS). The samples were stored at room temperature for 210 d and were periodically removed from storage to perform a sensory descriptive analysis. A consumer acceptance test was carried out on the fresh product (storage day 0) to evaluate flavor. All samples exhibited significant differences in their sensory attributes initially and after storage. Intensity ratings for oxidized and cardboard flavors increased during storage. NC showed the highest oxidized and cardboard intensity ratings (39 and 22, respectively) and NMC exhibited the lowest intensity ratings for these negative attributes (8 and 17, respectively) after 210 d of storage. Alternatively, the intensity ratings for sweetness and walnut flavors were decreased for all samples. NMC had the lowest decrease at the end of storage for these positive attributes (75.86 in walnut flavor and 12.09 in sweetness). The results of this study suggest a protective effect of the use of an edible coating to preserve sensory attributes during storage, especially for samples coated with MC. The results of the acceptance test showed that addition of the coating negatively affected the flavor acceptance for NMC and NCMC coated walnuts. Edible coatings help to preserve sensory attributes in walnuts, improving their shelf-life, however, these coatings may affect consumer acceptance in some cases.
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