Effect of zein coating enriched by addition of functional constituents on the lipid oxidation of roasted hazelnuts

Abstract

This study investigates the effects of hazelnut skin extract powder (HEP) and α‐tocopherol addition to zein coating on lipid oxidation, texture, and moisture content of roasted hazelnuts. Total phenolic content of hazelnut skin extracted with three different solvents (acetone, ethanol, methanol) under hot (50°C) and cold (29°C) conditions were determined. The highest phenolic content (652.6 mg GAE/g) was achieved by using methanol as solvent at 50°C. Uncoated and coated hazelnuts were subjected to accelerated shelf‐life testing at 40°C for 5 months. Peroxide value, free acidity, K232, and K270 values of oil fraction of hazelnuts were measured at each month as indicators of oxidative rancidity. All coatings significantly reduced the investigated parameters indicating that they are all effective in prevention of oxidation. α‐Tocopherol incorporated coating provided the lowest PV (1.21 meqO2/kg) and K232 (3.03) values at the end of storage period and also it has the smoothest outer surface appearance. Hardness values and moisture contents of coated and uncoated hazelnuts remained unchanged during storage. Practical applications Application of zein coating reduced the oxidative rancidity of roasted hazelnuts without producing significant changes in its color, texture, or moisture content at ambient storage conditions. Incorporation of α‐tocopherol improved the coating performance while incorporation of HEP did not at the level of 0.5% (w/v). This study shows that the shelf‐life of roasted hazelnuts may be enhanced by coating with zein solution containing natural antioxidant.

Effect of sodium alginate-calcium chloride coating and glycerol and sorbitol concentration on oxidative stability and fungal growth of Persian walnut (Juglans regia L.)

“…In their study, the acidity of uncoated walnut and pine nuts increased throughout the storage period compared to the coated ones, and the 3component coatings containing whey protein isolate, pea starch, and carnauba wax had the best effect on lipolysis prevention. Also, (Yildirim & Barutçu Mazi, 2017) reported AV increasing in all roasted hazelnut samples during storage and decreasing the rate of AV rising by incorporating skin extract and α-tocopherol into the coating formulation. The α-Tocopherol was more effective than the prevention of free FAs formation.…”

“…Therefore, SA coating and CaCl 2 treatment had a more protective effect on color parameters. (Yildirim & Barutçu Mazi, 2017) Reported no visible changes in roasted hazelnuts' L*, a*, and b* color parameters after coating with zein solutions compared to the uncoated sample. In a study by (Bastani et al, 2010), the shining appearance of carboxymethylcellulose-coated walnut kernels was higher than in other samples, and b* showed no significant difference during storage.…”

In a nutshell: prospects and challenges on coatings for edible kernels

“…The presence of Satureja intermedia extract boosted both antioxidant and antifungal activities of apricot gum coatings applied on almonds, in a dose‐dependent fashion . Likewise, the presence of catechin in soy protein isolate/CMC coatings improved their performance on walnuts, as did green tea extract in chitosan coatings on walnuts, α ‐tocopherol in zein coatings on roasted hazelnuts, and thyme essential oil in chitosan coatings on walnuts…”

Protein-Based Packaging Films in Food: Developments, Applications, and Challenges

“…Since proteins are susceptible to thermal denaturation, DBD cold plasma technology was applied to the production of chitosan and corn protein films, the thermal degradation temperature of the films was increased from 264 to 323.57 °C, and the thermal stability of the protein films was improved [25]. The addition of hazelnut skin powder extract and αtocopherol as oxidants to zein enhanced the antioxidant and bacteriostatic properties of films by reducing the free acidity and peroxide value [26]. The application of 10% clove essential oil (CEO) to a 30% concentration of corn alkyd protein film by the electrostatic spinning technique significantly improved the bacteriostatic properties of the cheese [27].…”