Napping and preference mapping reveals clustered consumer acceptability of walnut kernels in relation to chemical assays and texture profile

Abstract

Walnuts (Juglans regia L.) are valued for their nutritional profile and economic significance. Despite the advancement in cultivar development and production globally, growers face challenges such as the oxidation of unsaturated fatty acids during storage, leading to rancidity and consumer rejection. Local growers also need to identify the uniqueness of their products compared to overseas imports. Rapid profiling methods, such as Napping, have been developed to generate sensory characteristics at low cost, although no study has been conducted on walnuts. This study aimed to understand the driving factors of consumer acceptability of walnut kernels, in the context of the New Zealand market, using Napping combined with consumer preference mapping. The products were sourced commercially from the market. Physicochemical properties, including oxidation indices, color, moisture content, and texture profiles, were assessed. The sensory characteristics were profiled by Napping. The products were then tested for consumer acceptability. Products were sensorily distinct, differentiated mostly by creamy and rancid attributes. The preference mapping revealed that the preferred zones by most consumers corresponded to light brown, smooth, woody, sweet, fresh, and creamy attributes. Products featuring rancid and astringent are disliked by most consumers. Despite the commonality, two consumer clusters were identified. One cluster disliked those with high chemically measured oxidation, while the other cluster disliked those with high texturally measured resilience and springiness. These findings demonstrate that Napping, combined with Preference Mapping, offers a practical approach for small-scale producers to assess and improve the quality of walnut while probing the variability of consumer market.