High-humidity hot air impingement (HHAI), as an emerging thermal food processing technology, has recently been explored as a sustainable pretreatment approach for enhancing food products' drying performance and improving food quality. This critical review explores the fundamental mechanisms of HHAI, which involves markedly thinning the thermal boundary layer and steam condensing on the food surface and releasing latent heat to achieve rapid heating and microstructural modification of food materials. This review focuses on the application of HHAI technology as a pretreatment, with implications for drying efficiency and blanching, as well as food quality. This approach can reduce drying time by 4%–56% compared to untreated processes, with effective moisture diffusivity enhanced to 1.27 × 10 –10 –30.71 × 10 –10 m 2 /s. It achieves complete inactivation of key deteriorative enzymes, such as peroxidase and polyphenol oxidase, reducing their residual activity to below 5%. This method avoids the nutrient leaching and significant wastewater generation associated with conventional water blanching. Furthermore, HHAI pretreatment effectively preserves bioactive compounds, maintains texture, and reduces the total color difference and browning in products. The energy-saving potential and reduction in process wastewater are also discussed. Future research should focus on in-depth expansion and mechanistic integration in this domain, including extraction enhancement, process parameter optimisation, and safety framework establishment. Overall, HHAI pretreatment technology shows potential as a sustainable and effective tool for enhancing drying processes and improving the quality of foods.
Shuai et al. (Thu,) studied this question.