Effect of short-term storage on walnut fruit quality

Abstract

Two Hungarian and two introduced walnut cultivars were examined as fresh samples and under storage. Some important compositional data were determined in order to evaluate the differences between the cultivars and the changes after storage. The cultivars' oil contents were the same, but there was some difference in fatty acid composition; 'Alsószentiváni 117' had a higher mono-unsaturated fatty acid content than the others. Considering the oxidative stability, 'Alsószentiváni 117' contained good properties in all stages (induction time equals or higher than 10 h). Lower antioxidant capacity was measured in 'Chandler' samples compared to the others. 'Alsószentiváni 117' has higher α-and γ-tocopherol contents than the other cultivars studied. Two different drying methods were also compared in case of the Hungarian cultivars. The changes in compositional data showed no tendencies. We found that Hungarian cultivars were at least as valuable as the introduced ones.Keywords: walnut, short-term storage, fatty acid composition, tocopherols, antioxidant capacityThe Persian walnut (Juglans regia L.) is harvested from early September till mid-October in Hungary. After the harvest, it is necessary to remove the husk, wash, dry, size and pack the fruits or crack and pack the kernels. The peak selling period of this fruit crop is in November or during Advent, therefore a short storage is needed for the prepared walnut. The Hungarian bred walnut cultivars have good compositional value (BUJDOSÓ et al., 2010(BUJDOSÓ et al., , 2014 as published before. Our aim is to save the good fruit quality (light shell and kernel colour, good taste) and the good compositional value of the dried in-shell walnut. There is no protocol for walnut storage in Hungary; the growers mainly keep the fruit between 2 and 10 °C in a dark room. There are only a few papers on walnut storage. One study gives results on this topic, but focuses on evaluating the effect of low temperature (10 °C) on walnut fruit damage and reinfestation before shipping from California to avoid insect infections (JOHNSON et al., 2010). Whole walnut storage at 10 °C and relative humidity conditions of 60% gave the best results in order to save the original fruit quality (LOPEZ et al., 1995). Another research study stated that storage at 1 °C had a positive effect on saving total phenol compound content, total antioxidant content, and colour of the cultivars stored for 12 months compared to samples stored at 20 °C (CHRISTOPOULOS & TSANTILI, 2011). It has been found that tocopherol content of 'Franquette' and 'Hartley' stored at 4 °C decreased by 30% after less than 3 months (LAVEDRINE et al., 1997).

Responses of Persian walnut on foliar applications of different biostimulants

“…There are some possibilities for growers to increase the nut size and to enrich the phenolic compounds of kernels. Among the phenolics, ellagic acid, ferulic acid, gallic acid, catechin, vanillic acid, caffeic acid, sinapic acid, salicylic acid, rutin, and epicatechin were abundant in the kernel and seed coat ( Colaric et al., 2005 ; Bujdosó et al., 2014 ; Gharibzahedi et al., 2014 ; Kónya et al., 2015 ; Trandafir et al., 2016/a ; Rahmani et al., 2018 ; Kafkas et al., 2020 ; Trandafir and Cosmulescu, 2020 ; Shen et al., 2021 ; Medic et al., 2021/a ; Medic et al., 2021/b ; Li et al., 2023 ; Wu et al., 2023 ). Different papers reported quite similar quantities of phenolics in three different forms, however their sequence is always the same.…”