Effects of convection-, vacuum-and freeze-drying on antioxidant, physicochemical properties, functional properties and storage stability of stink bean (Parkia speciosa) powder

Comparative Analysis of the Impact of Three Drying Methods on the Properties of Citrus reticulata Blanco cv. Dahongpao Powder and Solid Drinks

Citrus reticulata Blanco cv. Dahongpao is a traditional Chinese citrus variety. Due to the high investment in storage and transport of Citrus reticulata Blanco cv. Dahongpao and the lack of market demand, the fresh fruit is wasted. The processing of fresh fruit into fruit drinks can solve the problem of storage and transport difficulties and open up new markets. Investigating the effects of different drying processes (hot air, freeze, and spray drying) on fruit powders is a crucial step in identifying a suitable production process. The experiment measured the effects of different drying methods (hot air drying, freeze drying, and spray drying) on the nutrient, bioactive substance, and physical characteristics of fruit powder. This study measured the influence of three different drying methods (hot air, freeze, and spray drying) on the nutritional, bioactive substance, and physical characteristics of fruit powder. The results showed that compared to vacuum freeze-drying at low temperature (-60 °C) and spray-drying at high temperatures (150 °C), hot air drying at 50 °C produced fruit powder with superior nutritional quality, higher levels of active substances, and better physical properties. Hot air drying produced fruit powder that had the highest content of amino acids (11.48 ± 0.08 mg/g DW), vitamin C (112.09 ± 2.86 μg/g DW), total phenols (14.78 ± 0.30 mg/g GAE DW), total flavonoids (6.45 ± 0.11 mg/g RE DW), organic acids, and antioxidant activity capacity. Additionally, this method yielded the highest amounts of zinc (8.88 ± 0.03 mg/Kg DW) and soluble sugars, low water content, high solubility, and brown coloration of the fruit powder and juice. Therefore, hot air drying is one of the best production methods for producing high-quality fruit powder in factory production.

Dietary Organosulfur-Containing Compounds and Their Health-Promotion Mechanisms

Dietary organosulfur-containing compounds (DOSCs) in fruits, vegetables, and edible mushrooms may hold the key to the health-promotion benefits of these foods. Yet their action mechanisms are not clear, partially due to their high reactivity, which leads to the formation of complex compounds during postharvest processing. Among postharvest processing methods, thermal treatment is the most common way to process these edible plants rich in DOSCs, which undergo complex degradation pathways with the generation of numerous derivatives over a short time. At low temperatures, DOSCs are biotransformed slowly during fermentation to different metabolites (e.g., thiols, sulfides, peptides), whose distinctive biological activity remains largely unexplored. In this review, we discuss the bioavailability of DOSCs in human digestion before illustrating their potential mechanisms for health promotion related to cardiovascular health, cancer chemoprevention, and anti-inflammatory and antimicrobial activities. In particular, it is interesting that different DOSCs react with glutathione or cysteine, leading to the slow release of hydrogen sulfide (H2S), which has broad bioactivity in chronic disease prevention. In addition, DOSCs may interact with protein thiol groups of different protein targets of importance related to inflammation and phase II enzyme upregulation, among other action pathways critical for health promotion.

Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Microwave Drying for Production of Rehydrated Foods: A Case Study of Stink Bean (Parkia speciosa) Seed

The potential of microwave drying in the production of rehydrated foods is demonstrated with stink beans (Parkia speciosa), smelly legumes of Africa and Asia. Compared to stink beans dehydrated by convective drying and freeze drying, the microwave products exhibit higher moisture contents, but the distribution of microscopic pores leads to good rehydration characteristics. Dehydration by microwave drying is also achieved within a much shorter period than that commonly used in freeze drying. The dehydration time can be further reduced to 6 h comparable to convective drying, and the moisture content is dropped to 11% by decreasing the pressure during microwave drying. However, the rehydration time remains around 65 min for products from both ambient and low-pressure (400 Pa) microwave drying. In rehydration, the period is successfully reduced to 30 min by increasing the water temperature to 70 °C. The results indicate that microwave drying does not affect the value of crude protein and rehydrated products are comparable to fresh stink beans. From these findings, the microwave drying technique is an applicable technology for both manufacturers and consumers, with acceptable drying time and rehydration characteristics.