Convenient use of low field nuclear magnetic resonance to determine the drying kinetics and predict the quality properties of mulberries dried in hot-blast air

Sodium carboxymethyl cellulose hydrogels containing montmorillonite-NaClO2 for postharvest preservation of Chinese bayberries

Owing to their lack of outer skin, Chinese bayberries are highly susceptible to mechanical damage during picking, which accelerates bacterial invasion and rotting, shortening their shelf life. In this study, montmorillonite (MMT) was used to absorb an aqueous sodium chlorite solution embedded in a carboxymethyl cellulose sodium hydrogel after freeze drying, and the hydrogel was crosslinked by Al3+ ions. Al3+ hydrolyzed to produce H+, creating an acidic environment within the hydrogel and reacting with NaClO2 to slowly release ClO2. We prepared a ClO2 slow-release hydrogel gasket with 0.5 wt% MMT-NaClO2 and investigated its storage effect on postharvest Chinese bayberries. Its inhibition rates against Escherichia coli and Listeria monocytogenes were 98.84% and 98.96%, respectively. The results showed that the gasket preserved the appearance and nutritional properties of the berries. The antibacterial hydrogel reduced hardness loss by 26.57% and ascorbic acid loss by 46.36%. This new storage method could also be applicable to other fruits and vegetables.

Prevention of the Quality Degradation of Antarctic Krill (Euphausia superba) Meal through Two-Stage Drying

To achieve a krill meal of high quality, a two-stage drying involving hot-air drying and vacuum drying was investigated. Five experimental groups were established according to the different drying conditions in the second stage, including 95 °C and 101 kPa, 95 °C and 60 kPa, 75 °C and 101 kPa, 75 °C and 60 kPa, and 75 °C and 20 kPa. The results showed that reducing the drying temperature and vacuum pressure in the second stage had a significant impact on the drying characteristics, sensory quality, and bioactive compounds of krill meal. Among all five groups, the drying condition of 75 °C and 60 kPa maintained a high drying rate while preserving a phospholipid content of 30.01 mg/kg and an astaxanthin content of 37.41 mg/kg. It also effectively reduced the isomerization of astaxanthin and the oxidation of unsaturated fatty acids. These results suggested that the two-stage drying method may contribute to the production of high-quality krill meal.

Effects of ultrasonic power on drying kinetics and product quality of licorice extract during ultrasound-assisted vacuum drying

BACKGROUND

Licorice extract is an important raw material for food additives and medicine. The quality of licorice extract is dictated by the drying process. The commonly used drying methods of licorice extract are not efficient in obtaining high-quality products so alternative techniques need to be developed and researched. In this study, ultrasound-assisted vacuum drying (UAVD) was first utilized to improve drying efficiency and produce a higher-quality product. The changes in water mobility of licorice extract during drying were characterized using low-field nuclear magnetic resonance. In addition, the effects of ultrasonic power on the drying dynamics, the contents of liquiritin and glycyrrhizic acid, the antioxidant capacity and the microstructure formation of licorice extract during the whole drying process were investigated.

RESULTS

The drying times for licorice extract to reach equilibrium moisture content were reduced by 9.09-69.70% with UAVD at 40-200 W compared with that without ultrasonic treatment (0 W). Moreover, the proportions of bound water and semi-bound water in fresh concentrate were 3.75% and 96.25%. It was also found that high ultrasonic power promoted the flow of water and the formation of porous structure in licorice extract, which led to the improvement of drying efficiency. The contents of liquiritin (2.444%) and glycyrrhizic acid (6.514%) were retained to a large degree in the dried product at an ultrasonic power of 80 W. The DPPH inhibition rate of UAVD samples with different ultrasonic powers ranged from 84.07 ± 0.46% to 90.65 ± 0.22%.

CONCLUSION

UAVD has the advantages of high efficiency and low energy consumption, which may be an alternative technology for vacuum drying widely used in industry. © 2024 Society of Chemical Industry.

Ultrasound pretreatment enhances moisture migration and drying quality of mulberry via microstructure and cell-wall polysaccharides nanostructure modification

The effects of ultrasound pretreatment (20 kHz, 30 W/L) on mulberries' texture, microstructure, characteristics of cell-wall polysaccharides, moisture migration, and drying quality were investigated over exposure times ranging from 15 to 45 min. Ultrasound induced softening of mulberry tissue, accompanied by an increase in water-soluble pectin and a decrease in chelate-soluble pectin and Na2CO3-soluble pectin concentrations. Noticeable depolymerization of the pectin nanostructure was observed in the pretreated mulberries, along with a decrease in molecular weight, attributed to side-chain structure cleavage. Ultrasound loosened the cell wall structure, increased free water content and freedom, thereby reducing water diffusion resistance. Ultrasound pretreatment reduced drying time by 11.2 % to 23.3 % at various processing times compared to controls. Due to significantly enhanced drying efficiency, the optimal pretreatment time (30 min) yielded dried mulberries with higher levels of total phenolics and total anthocyanins, along with an increased antioxidant capacity. The results of this study provide insights into the mechanisms by which ultrasound pretreatment can effectively enhance the mulberry drying process.

Ripening induced degradation of pectin and cellulose affects the medium-and short-wave infrared drying characteristics of mulberry

Mulberries were categorized into five stages of ripening (D1-D5, 0.905-1.055 g/cm3) based on their density, and their physicochemical properties, tissue structure, cell wall polysaccharide properties, and drying characteristics were investigated. As mulberry ripening progressed, the TSS and water-soluble pectin content rapidly increased, while the contents of TA, hardness, chelate-, sodium carbonate-soluble pectin, hemicellulose, and cellulose decreased gradually. Pectin nanostructure and monosaccharide composition indicated that both the main and side chains of pectin undergo depolymerization. Medium- and short-wave infrared drying time initially decreased and then increased during mulberry ripening, with D4 fruits exhibiting the shortest drying time. Compared with D4 fruits, the collapse of cell structure in D5 fruits prolongs their drying time. The results demonstrate that ripeness significantly affects mulberry drying characteristics, which is related to changes in cell structure and pectin properties. Utilizing mulberry density to determine ripeness and grading is an effective approach to achieving optimal drying.

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.

Advances in the Chemistry, Analysis and Adulteration of Anthocyanin Rich-Berries and Fruits: 2000-2022

Anthocyanins are reported to exhibit a wide variety of remedial qualities against many human disorders, including antioxidative stress, anti-inflammatory activity, amelioration of cardiovascular diseases, improvement of cognitive decline, and are touted to protect against neurodegenerative disorders. Anthocyanins are water soluble naturally occurring polyphenols containing sugar moiety and are found abundantly in colored fruits/berries. Various chromatographic (HPLC/HPTLC) and spectroscopic (IR, NMR) techniques as standalone or in hyphenated forms such as LC-MS/LC-NMR are routinely used to gauge the chemical composition and ensure the overall quality of anthocyanins in berries, fruits, and finished products. The major emphasis of the current review is to compile and disseminate various analytical methodologies on characterization, quantification, and chemical profiling of the whole array of anthocyanins in berries, and fruits within the last two decades. In addition, the factors affecting the stability of anthocyanins, including pH, light exposure, solvents, metal ions, and the presence of other substances, such as enzymes and proteins, were addressed. Several sources of anthocyanins, including berries and fruit with their botanical identity and respective yields of anthocyanins, were covered. In addition to chemical characterization, economically motivated adulteration of anthocyanin-rich fruits and berries due to increasing consumer demand will also be the subject of discussion. Finally, the health benefits and the medicinal utilities of anthocyanins were briefly discussed. A literature search was performed using electronic databases from PubMed, Science Direct, SciFinder, and Google Scholar, and the search was conducted covering the period from January 2000 to November 2022.

Maltodextrin Moderated Microwave Osmotic Dehydration of Mango Cubes with Finish Air-Drying: Optimum Considerations

The microwave osmotic dehydration of mango cubes under the continuous flow of maltodextrin moderated sucrose solution spray (MWODS) was evaluated based on the quality of the finish air-dried product. Experiments were designed according to a central composite rotatable design to evaluate the effect of maltodextrin moderated sucrose solution [sucrose + maltodextrin (10DE) at a proportion of 85:15] on the finish air-dried product. The process variables were temperature (30 to 70 °C), solute concentration (30 to 70%), contact time (10 to 50 min) and flow rate (0.8 to 3.8 L/min). The optimum processing conditions were determined based on several processes and product-related quality parameters such as moisture loss (ML), solids gain (SG), weight gain, ML/SG, color, texture, rehydration capacity (RHC), bulk density and drying time. The MWODS contact time was the largest significant contributor with respect to most of the parameters, followed by temperature. The optimum values found were an osmotic treatment temperature of 51.7 °C, a solute concentration of 58.5%, a contact time of 30.6 min and a solution flow rate of 1.8 L/min. Finally, these optimized processing conditions were used to compare three different solute mixtures [sucrose only, sucrose + dextrose and sucrose + maltodextrin (10DE) at a ratio of 85:15%] to understand the effect of various solutes on the quality of the finished dried product. Based on the color and textural parameters, along with the RHC, of the finished product, the sucrose + maltodextrin mixture was shown to result in the most desirable quality and the air-dried product without MWODS pretreatment (control) resulted in the least desirable. Overall, the results suggest that the sucrose + maltodextrin combination offered an advantage in terms of quality for the MWODS air-drying of mango cubes.