Effect of storage conditions on chemical and physical characteristics of hazelnut (Corylus avellana L.)

This study evaluated the effect of different storage conditions currently used by the industry, on the chemical, physical and sensory characteristics of ‘Tonda Gentile delle Langhe’ hazelnuts, during one year of storage. The traditional method of in-shell preservation in a storage room at ambient temperature was compared with refrigerated storage of shelled nuts at 4 °C and 55% relative humidity, with or without modified atmosphere (1% oxygen, 99% nitrogen). The following parameters were measured: moisture content, lipid content, total phenolic content, and antioxidant capacity of the kernel; acidity and peroxide value of the oil. The kernel resistance to breakage was evaluated by texture analysis using a compression test. The hazelnuts were also evaluated by sensory analysis. The results showed that the acidity and the peroxide value were the most discriminating parameters. After one year of storage, the acidity of hazelnuts stored at ambient temperature (0.47% oleic acid) was higher than the value considered the acceptable limit after storage (0.40% oleic acid), while refrigerated storage maintained a low level of acidity and lipid oxidation, with the best performance in modified atmosphere (0.13% oleic acid; 0.057 O2 mmol kg−1). Sensory analysis after 12 months also showed differences among the three storage treatments. In-shell storage of hazelnuts at ambient temperature was able to preserve the kernels below threshold limits of acidity and oxidative degradation for up to 8 months, but refrigeration was necessary to maintain high quality for up to one year. The use of modified atmosphere is recommended for long periods of storage.

► The effect of three storage conditions on quality parameters of hazelnuts was studied in commercial scale conditions.
► Time and storage conditions affected significantly acidity and peroxide value.
► Low temperature and modified atmosphere (1% oxygen, and 99% nitrogen) decreased additively the lipid oxidation.
► Low temperature maintained high level of phenolic content and antioxidant capacity.