Compositional Characteristics, Texture, Shelf-Life and Sensory Quality of Sweet Walnut Pastes

Abstract

Walnut pastes represent a promising functional food product due to the nutritional value of walnuts (Juglans regia L.). However, little is known about the impact of formulation and processing on their stability during storage. This study aimed to assess the effect of formulation and processing variables conditions for walnut paste production and to evaluate the physicochemical, textural, microbiological, and sensory stability of the product over time. A complete factorial design was used to develop pastes with varying walnut content (70%, 80%, and 90%) using both roasted (120°C for 20 min) and unroasted walnuts. Ingredients such as sugar, soy lecithin, salt, ascorbic acid, potassium sorbate, and antioxidants were proportionally adjusted. All formulations were stored at 4°C for 180 days. The oxidative stability index ranged from 25.39 to 16.84 h, with higher stability observed in samples containing synthetic antioxidants. Peroxide values and conjugated diene levels remained lowest in formulations containing butylated hydroxytoluene. Acidity values stayed below 0.50 mg KOH/g oil, indicating negligible lipid hydrolysis. Roasting significantly improved spreadability and smoothness, as confirmed by instrumental and sensory analysis. No microbial growth of Escherichia coli, Salmonella spp., Clostridium perfringens, or Penicillium aurantiogriseum was detected in any sample throughout storage. These findings evidence that appropriate formulation and roasting can enhance both the oxidative stability and sensory quality of walnut pastes, demonstrating their potential as a stable and health spreadable product.