Enhancing drying efficiency and quality of seed-used pumpkin using ultrasound, freeze-thawing and blanching pretreatments

Effects of ultrasonic pretreatment on drying characteristics and water migration characteristics of freeze-dried strawberry

The effects of ultrasonic pretreatment on the drying characteristics and microstructure of strawberry slices were investigated. The rehydration characteristics of freeze-dried products, which were pre-frozen at -20 °C and - 80 °C were explored, with a focus on water mobility and distribution. The ultrasonic pretreatment significantly increased the water mobility of the strawberry slices, resulting in a reduction in their water content. However, the application of ultrasound significantly decreased the rehydration speed, indicating a lower moisture absorption capacity in the pretreated sample. The micrographs revealed that the structure of the tissue was more uniform after ultrasonic treatment, and water loss was accelerated. In addition, the contact angle measurements showed that the samples were more hydrophobic after ultrasonic treatment, and the eutectic temperature and fold point of the samples increased. Therefore, this study found that ultrasonic-assisted freeze vacuum drying technology effectively reduces hygroscopicity, improves product storage, and represents a potential method for dried production.

Revealing the mechanism of post-harvest processing on rose quality based on dynamic changes in water content, enzyme activity, volatile and non-volatile metabolites

Existing studies on post-harvest processing of edible roses have mainly focused on processing techniques and physicochemical properties of the final dried products, with limited studies on how changes in metabolites during processing affect the quality of these products. This study investigated changes in water content and status, enzyme activity, phenolic compounds, and volatile and non-volatile compounds during processing and revealed the mechanisms by which post-harvest processing (drying without blanching (WBD) and drying with blanching (BD)) affects the quality of dried roses by establishing their correlations. Results showed that the blanching reduced the relative content of free water and water activity, thus reducing the subsequent drying time and enzyme activity. The BD method caused higher levels of phenolic compounds than the WBD method in terms of gallic acid, ellagic acid, epicatechin, and quercetin. The OPLS-DA analysis identified 6 differential volatiles out of 72 detected volatiles, contributing to the unique aroma of dried roses by activating olfactory receptors through hydrogen bonding and hydrophobic interactions. 58 differential metabolites were screened from 964 non-volatile metabolites. KEGG pathway analysis revealed that the changes in volatile and non-volatile metabolites induced by different processing methods were due to the effect of blanching on glutathione and fatty acid metabolism. These findings provide a comprehensive understanding of how post-harvest processing affects the quality of dried roses.

Investigation on epidermal structure and water migration of postharvest passion fruit during storage

Passion fruit is a tropical fruit that has plenty of fruit fragrance. During storage, passion fruit quickly loses water, resulting in its poor quality. Researching the mechanism of water loss contributes to prolonging the storage time. In this study, passion fruit was stored at 7 or 25°C to analyze the relationship between epidermal structure and water migration. The epidermal wax and structure of passion fruit began to show signs of destruction from the middle stage (day 8) during storage. The mobility of free water was decreased at 7°C and increased at 25°C in passion fruit from the middle stage of storage (day 8). The migration rate of free water in passion fruit stored at 7°C was lower than that at 25°C. The mobility of immobile water was weaker in the late storage period but that of bound water changed barely. These results showed that the migration of free, immobile, and bound water had a connection with the epidermal structure. Incomplete epidermal structure promoted water loss in passion fruit, with the most pronounced loss of free water. PRACTICAL APPLICATION: Maintaining the epidermal structure of passion fruit well can decrease the water loss ratio. Passion fruit stored at low temperatures could better sustain the integrity of epidermal wax and structure; it was able to change the water migration rate in the epidermis of passion fruit, which was conducive to maintaining the water content.

Changes in polyphenolic compounds and antioxidant activities of seed-used pumpkin during hydrothermal treatment

An environmentally friendly physical processing method, hydrothermal treatment (HT), was used to increase the content of specific compounds and antioxidant activities of seed-used pumpkin byproducts. The influence of hydrothermal temperature (80 °C-160 °C) and time (30-150 min) on changes in polyphenols and antioxidation was evaluated. The results revealed that the maximum free polyphenol content (140 °C for 120 min) was 3.96-fold higher than the untreated samples. Elevated temperature and long duration changed phenolic acid contents. For example, p-coumaric acid, rutin and chlorogenic acid exhibited a decreasing trend, and p-hydroxybenzoic acid, quercetin and cinnamic acid showed an increasing trend. Compared to controls, HT was significantly associated with increased antioxidant activities. To comprehensively reveal the influence of hydrothermal temperature and time on changes in polyphenolic content, back propagation artificial neural network (BP-ANN) models with accurate prediction ability were developed, and the results exhibited well-fitted and strong approximation ability (R² > 0.95 and RMSE < 2 %) and stability.

Ultrasound applications in drying of fruits from a sustainable development goals perspective

This review focuses on the many contributions of ultrasound technologies for fruit drying toward the United Nations Sustainable Development Goals (SDG). Along this review, several aspects attained from the application of ultrasound technologies are correlated with the SDGs. The main ultrasonic technologies applied for fruit drying, such as ultrasonic bath, probe ultrasound, air-borne ultrasound air-drying, and ultrasound-assisted contact air-drying, are presented. An in-depth discussion on ultrasound contributions, its advantages, disadvantages, and limitations are made. The effects of ultrasound on water diffusivity in several fruits are presented by correlating this effect with drying time and cost of energy. Ultrasound-assisted fruit drying, like other food processing technologies, directly impacts Zero Hunger, but ultrasound technologies contribute to much more than delivering long shelf-life food. This technology can be used to produce healthy foods and provide well-being, which will be discussed by correlating the effects of ultrasound-assisted air-drying with the concentration of nutritional compounds. Ultrasound-assisted fruit drying reduces wastewater toxicity and energy consumption and improves productivity, potentially improving workplaces and salaries. A walk through the technology is presented from Zero Hunger to No Poverty.

Utilization of pumpkin, pumpkin powders, extracts, isolates, purified bioactives and pumpkin based functional food products: A key strategy to improve health in current post COVID 19 period: An updated review

Progression of today's world has been given setback due to the adversity of a novel, viral and deadly outbreak COVID 19, which raised the concerns of the scientists, researchers and health related officials about the inherent and adaptive immune system of the living body and its relation with healthy diet balanced with pharma foods. Choice of right food can help to build and boost adaptive immunity and pumpkin due to excellent profile of functional and nutraceutical constituents must be the part of both infected and non-infected person's daily diet. Vitamins, minerals, phenolic acids, essential oils, peptides, carotenoids and polysaccharides present in pumpkin could accommodate the prevailing deficiencies in the body to fought against the pathogens. Pumpkins are well equipped with nutraceuticals and functional ingredients therefore, consumption and processing of this remarkable fruit must be encouraged as pharma food due to its antihyperlipidemic, antiviral, anti-inflammatory, antihyperglycemic, immunomodulatory, antihypertensive, antimicrobial and antioxidant potential, and these pharmacological properties of pumpkin are directly or indirectly related to the COVID 19 outbreak. Utilization of pumpkin has a domain in the form of powders, extracts, isolates, and pumpkin incorporated food products. A wide range of healthy, nutritious and functional food products has been developed from pumpkin, which includes juice, soup, porridge, chips, biscuits, bread, cake, bar and noodles. In recent times some innovative and novel technologies have been applied to process and preserve pumpkin for its enhanced shelf life and bioaccessibility of nutrients. Need of healthy eating in current post COVID 19 period is very crucial for healthy population, and medicinal foods like pumpkin, and bioactive compounds present in this functional food could play a vital role in developing a healthy community around the globe.