Effects of Drying Methods, Temperature, and Initial Moisture Content on Drying Characteristics, Nutritional Quality, Texture, and Oxidative Stability of Peanuts

This study systematically investigated the combined effects of drying method (mid- and short-wave infrared drying, MSID; hot air drying, HAD; radio frequency-hot air combined drying, RF-HAD), drying temperature (35, 45, 55, 60 °C), and initial wet-basis moisture content (20%, 25%, 30%) on drying characteristics, nutritional quality, texture, and oxidative stability of peanuts. RF-HAD achieved the shortest drying time, followed by MSID and HAD. Protein content remained stable across all treatments. Fat, oleic acid, and total amino acids were significantly affected by all three factors with significant two-way interactions; linoleic acid exhibited significant method × moisture and three-way interactions. Hardness, adhesiveness, springiness, gumminess, and chewiness showed significant three-way interactions, indicating interdependent effects. All samples met national standards for acid value and peroxide value. MSID yielded the lowest acid value and peroxide value immediately after drying, suggesting better initial oxidative quality. Acid value was primarily influenced by method and temperature, with significant two-way interactions, whereas peroxide value showed significant main effects and a highly significant three-way interaction. No single drying condition optimized all quality attributes. RF-HAD excels in drying efficiency and texture enhancement but requires temperature control to limit oxidation; MSID offers superior initial oxidative stability and amino acid retention. Initial moisture content acts as an active variable that modulates the effects of drying method and temperature.