Nonenzymatic Browning Criteria to Sea Buckthorn Juice during Thermal Processing

Nonenzymatic browning reaction is responsible for color and quality changes of fruit juices during thermal processing, and reasonable criteria are crucially important for establishing good manufacturing practice. The nonenzymatic browning criteria of thermally treated sea buckthorn juice from 90 to 120C, i.e., the absorbance at 420 nm (A₄₂₀ₙₘ) and color difference (ΔE*), were investigated. The values of L*, a*, b* and the content of ascorbic acid of sea buckthorn juice during thermal treatment could be fitted to first‐order kinetics, while the formation of 5‐hydroxymethylfurfural (5‐HMF) followed a zero‐order kinetics. The changes of ΔE* and A₄₂₀ₙₘcould be estimated by integrated models. The thermal processing parameters for sea buckthorn juice were optimized using kinetic models with low level of 5‐HMF and high content of ascorbic acid, and it was found that the thermal processing should be performed at 110C for 0.585 min. Estimation of the activation energy showed that A₄₂₀ₙₘcould be a reasonable indicator for evaluating the nonenzymatic browning of thermally processed sea buckthorn juice from 90 to 110C and ΔE* could be a valuable index at 120C. PRACTICAL APPLICATIONS: For fruit juice (puree) processing, optimal parameters are critically important to manufacture products with high quality. During thermal processing, vitamin C degradation, 5‐hydroxymethylfurfural accumulation and nonenzymatic browning occur simultaneously. The high quality includes the high vitamin content, the favorable appearance, the smallest color difference between raw material and final product, etc. This article discussed color changes of sea buckthorn juice, a superfruit juice specialized in high vitamin C content and low pH value, during thermal sterilization. Absorbance at 420 nm (A₄₂₀ₙₘ) and color differences (ΔE*), two indicators in controlling nonenzymatic browning during juice processing, were evaluated with kinetic models and used to optimize the thermal processing. Furthermore, the activation energy calculation of A₄₂₀ₙₘand ΔE* revealed the reasonable criteria on juice quality controlling. All the quality control criteria in this paper showed a guideline of quality control in practical juice manufacturing.