No abstract

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.

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. RESUMEN: Conservación de la calidad de los granos de nueces utilizando recubrimientos comestibles. El objetivo de este trabajo fue evaluar el comportamiento de cubiertas comestibles para preservar la calidad de nueces (W). Tres tipos de cubiertas fueron estudiadas: carboximetilcelulosa (CMC), metilcelulosa (MC) y aislados proteicos de suero de leche (WP). Las nueces con y sin cobertura (WC) fueron almacenadas durante 210 días a temperatura ambiente (23 ± 2 °C). WC presentó los valores más altos para indicadores químicos de oxidación lipídica (índice de peróxidos (PV) = 3,06 meqO 2 /kg; dienos conjugados (CD) = 3,01 y trienos conjugados (CT) = 0,31) y para volátiles de oxidación (pentanal, nonanal, hexanal y decane,5,6-bis(2,2-dimethylpropylidene). Por el contrario, WMC presentó los menores PV (1,20 meqO2/kg), CD (2,26) y CT (0,17) y la menor desaparición de carotenoides (0,60 mg/kg). El valor L* medido en el aceite de nuez decreció en todos los tratamientos. Las cubiertas comestibles MC, CMC y WP exhibieron efecto protector en el deterioro de las nueces. MC fue la que presentó mejor comportamiento.ORCID ID: Grosso AL https://orcid.org/0000-0003-3174-5745, Asensio CM https://orcid.org/0000-0003-0744-9188, Nepote V https://orcid.org/0000-0002-0615-5316, Grosso NR https://orcid.org/0000-0002-1709-9671 Citation/Cómo citar este artículo: Grosso AL, Asensio CM, Nepote V, Grosso NR. 2018. Quality preservation of walnut kernels using edible coatings. Grasas Aceites 69 (4), e281. https://doi.

Walnut kernels contain high amounts of polyunsaturated fatty acids that determine a limited shelf life on these nuts. The application of walnut phenolics as antioxidants through a walnut protein-based coating, obtained from walnut oil cake residue, can help to increase the shelf life of walnuts. The objective was to evaluate the preservative effect of walnut polyphenols included in a walnut-proteic edible coating on walnut kernels. Three treatments of walnuts coated with walnut flour were prepared: without the addition of antioxidants (control); with the addition of a walnut phenolic extract; and with the addition of butylated hydroxytoluene (BHT). On the last storage day, the sample with the addition of walnut phenolics presented a lower peroxide (3.64 meq 0 2 /kg oil) and anisidine value (1.11), conjugated diene (15.92), and hexanal content (19.67 × 10 6 e.c.) than the control sample (6.23, 1.81, 24.65, and 122.37 × 10 6 e.c., respectively). Also, on the last day, the control sample showed the highest deterioration of polyunsaturated fatty acids (from 74.83 to 71.08 g/100g), carotenoid (from 3.43 to 1.90 mg/kg), and γ-tocopherol content (from 349.66 to 298.42 mg/kg). In addition, this sample exhibited the highest oxidized (20.33) and the lowest walnut flavor intensity (64.67) on day 84. Regarding consumer acceptance, the phenolic-added sample displayed a greater flavor acceptance score. Walnut phenolics, implemented through a walnut protein-based coating, improve the preservation of walnuts.

Oxidative rancidity is one of the major causes of peanut quality deterioration. The in‐shell nut industry's greatest concern is to preserve high quality and extended the shelf life of these products. This research determined the sensory and chemical stabilities of raw in‐shell high‐oleic and normal‐oleic peanuts during long‐term storage. In‐shell peanuts samples of normal‐ and high‐oleic types were stored at room temperature (23 °C) for 675 days. The quality parameters, like the fatty acid composition, moisture content, free fatty acids (FFA), peroxide value (PV), conjugated dienes (CD), and p‐anisidine value (pAV), as well as sensory attributes, were analyzed every 45 days. High‐oleic samples showed a 4.36‐fold higher oleic acid/linolenic acid (O/L) ratio (O/L = 10.65) than normal‐oleic peanuts (O/L = 2.44). FFA, PV, CD, pAV, and oxidized and cardboard flavors increased in all stored samples but especially in normal‐oleic peanuts. Conversely, roasted peanutty flavor decreased in all samples during storage but in lower proportion in high oleic peanut samples. The sensory and chemical changes that occurred in unshelled normal‐ or high‐oleic peanut samples were not remarkable, suggesting that the shell may protect peanut kernels against deterioration. However, in‐shell high‐oleic samples show greater stability and shelf life than normal‐oleic peanuts under the studied storage condition. Practical Application Quality preservation of peanuts is important for the food industry using peanuts as an ingredient. Peanut processors are concerned as to the best ways to preserve peanut quality for long‐term storage. Raw high oleic peanuts kept in the shells show better preservation of their sensory and quality properties during storage. In‐shell peanuts constitute an appropriate alternative to preserve chemical and sensory properties of this product.

This study analyzed the ability of defatted peanut flour packaging to preserve chemical quality stability of sunflower seeds throughout storage. Sunflower seed samples packaged in defatted peanut flour pouches (RS‐DPFP), high‐barrier plastic pouches made of ethylene vinyl alcohol (RS‐EVOH) and plastic pouches made of polyethylene (RS‐PE) were stored for 30 days at room temperature. Peroxide values and conjugated dienes showed a lower increase in RS‐DPFP and RS‐EVOH than in RS‐PE samples during storage. The samples packaged in DPFP pouches exhibited similar changes in oleic/linoleic acid ratio and iodine value with respect to EVOH pouches during storage. A higher decrease in α‐tocopherol was observed in RS‐PE compared to RS‐DPFP and RS‐EVOH. After 30 days, RS‐PE presented the highest hexanal, 2‐octenal (E), hexanoic acid, and 1‐pentanol contents. DPFP delayed sunflower seeds deterioration, improving their shelf life during storage.