Antioxidants in Shell and Nut Yield Components after Ca, Mg and K Preharvest Spraying on Hazelnut Plantations in Southern Chile

Abstract

To determine the effects of pre-harvest calcium (Ca), magnesium (Mg) and potassium (K) spraying on the antioxidant activity and capacity of hazelnut (Corylus avellana L.) shells, as an approach to sustain the utilization of the main residue derived from this industry, four commercial hazelnut (Tonda di Giffoni) orchards located in Southern Chile (Cunco, Gorbea, Perquenco and Radal), during the 2018/19 season were sprayed three times with five combinations of Ca (300 and 600 mg L−1), Mg (300 and 600 mg L−1) and K (300 and 600 mg L−1). Yield components were determined in harvested whole nuts, whereas Ca, Mg and K concentrations, as well as total phenolic compounds, free radical scavenging antioxidant activity, and oxygen radical absorbance capacity, were determined in shells. All spray treatments with both Ca, Mg and K combinations showed a significant interaction between locality and treatment (L × T) on increased stabilized nut yield (kg ha−1) in comparison with the control treatments, whereas nut quality was differentially affected by treatment and orchard locality, thus confirming a significant L × T relationship regarding nut length and kernel yield. However, locality showed a major effect on kernels and shells. A significant relationship was determined between locality and the Ca, Mg and K spraying (L × T) concerning antioxidant compounds such as phenolics, whose amounts exceeded those of the control treatments by three times. Antioxidant capacity and activity in shells showed a significant L × T relationship, and nutshells collected from Cunco showed remarkably (3–4 times) higher levels of these factors than the other evaluated localities. Interactions between spray treatment and orchard location were responsible for the different values obtained in the experiments, confirming the influence of the environment on the efficacy of the treatments. Finally, these shells are worth further study as an interesting residue of the hazelnut industry due to their nutritional and antioxidant properties.

Hazelnut and Walnut Nutshell Features as Emerging Added-Value Byproducts of the Nut Industry: A Review

“…Chile has become the main producer country from the Southern Hemisphere, with an off-season nut supply of approximately 52,100 t (4.73% of total world production) in the 2021/2022 season [18] and an estimated production of 136,000 t year −1 for 2030 [18,19]. This nutshell has a mass value of over 50% of the total fruit weight (w/w) in stabilized nut [9,20]. It is becoming the main hazelnut byproduct production.…”

“…Regarding the hazelnut antioxidant features, Manterola-Barroso et al [9] reported a mean ORAC antioxidant capacity (AC) of 2119 µmol TE g −1 DW in control treatments of TDG shell samples, demonstrating the interesting antioxidant potential of hazelnut shells. Moreover, Pelvan et al [32] have reported AC (ORAC method) values from roasted hazelnut skin samples, which could be a part of and an approach to the antioxidant capacity of the hazelnut shell of approximately 1219 µmol TE g −1 , also TPC content (Folin-Ciocalteu) of 72.25 mg GAE g −1 and RSA (DPPH method) of 1.01 mg mL −1 (extract).…”

“…All the previous authors' findings were based on methanolic extracts of hazelnut and walnut shell samples from several origins. Moreover, it is important to highlight that the inconsistencies in antioxidant determinations (RSA, ORAC and TPC) among the authors could be attributed to environmental factors, as Manterola-Barroso et al [9] reported, including weather and plantation conditions, as well as the evaluated genotype. Regarding both nutshell species' antioxidants features, there was not enough information, probably due to their main application and research area, which is closely related to the ash production as raw material for amendment by pyrolysis.…”

“…Barbu et al [7] reported that shell residues derived from walnuts and hazelnuts comprise an amount of 646,818 and 353,807 t, respectively, each year. For the last decade, nutshells have been receiving much increasing interest because of their biochemical performances [8,9], and the nutshells in both species have gained attention as the main byproduct of each productive industry. Considering nutshell weight value (50% and reaching up to 60% w/w) [8], the utilization of nutshells for the extraction of phenolic compounds has been explored, with the purpose of obtaining natural valued additives (Figure 1).…”

“…Contini et al [10] reported interesting concentrations of total phenolic compounds (TPC) in the shells of hazelnut samples (56.6 mg GAE g −1 DW) for cultivars Tonda Gentile Romana, Tonda di Giffoni (TDG), Tonda Gentile delle Langhe and Tombul processed at different roasting temperature and times. In addition, Manterola-Barroso et al [9] reported an oxygen radical absorbance capacity (ORAC) of approximately 2100 µMol TE g −1 DW in shell samples of cultivar Tonda di Giffoni. In relation to their chemical composition, ranges of hemicelluloses (25-30%), cellulose (26-34.6%), lignin (40-43%) and extractives (3.3-4%) content have been reported [7,11,12].…”