Investigation on water status and distribution in broccoli and the effects of drying on water status using NMR and MRI methods

Effect of maturity on the drying characteristics of lotus seed and molecular structure, gelation and digestive properties of its starch

Maturity and drying treatment are important factors affecting the processing characteristics of lotus seeds and its starch. This study aimed to investigate the effect of maturity (from low to high-M-1, M-2, M-3, M-4) on far-infrared drying kinetics of lotus seeds, and on the variation of structure, gelation and digestive properties of lotus seed starch (LSS) before and after drying. As the maturity increased, the drying time reduced from 5.8 to 1.0 h. The reduction of drying time was correlated with the decrease of initial moisture content, the increase of water freedom and the destruction of tissue structure during ripening. The increased maturity and drying process altered the multiscale structure of LSS, including an increase in amylose content, disruption of the short-range structure, and a decrease in relative crystallinity and molecular weight. The viscosity, pasting temperature and enthalpy of LSS decreased during ripening, and drying treatment caused the further decrease. The digestibility of LSS increased during ripening and drying. Lotus seeds at M-4 would be optimal for obtaining shorter drying time, lower pasting temperature and enthalpy, and higher digestibility. This study provided theoretical guidance for achieving effective drying process and screening LSS with suitable processing properties through maturity sorting.

Insight into the changes in active metabolite profiles of noni (Morinda citrifolia L.) fruit subjected to different drying treatments

Noni fruit is renowned for its abundance of bioactive compounds. Drying is an important method for processing functional products derived from noni. However, limited information exists on how drying methods affect the active metabolite profiles of noni fruit. This study investigated the impact of four common drying methods, including hot-air drying (HAD), vacuum freeze drying (VFD), microwave drying (MWD), and far infrared drying (FID), on the physicochemical indexes, bioactive components, and functional properties of dried noni fruit slices using targeted and untargeted metabonomics analysis. The results showed significant variations in appearance, water migration, and microstructure of dried noni fruit slices subjected to the four drying methods. VFD treatment yielded better dried noni fruit products when compared to other drying methods. The superiority of VFD treatment was due to its uniform stratification, reduced collapse, better retention of bioactive components and antioxidants, and higher enzyme inhibitory rates. These findings suggest that VFD method is ideal for obtaining premium bioactive profiles and maintaining the biological activity of noni fruit.

Effect of chitosan coating, carbon dots and ultrasound treatment on microorganisms and physicochemical quality of fresh-cut lettuce

The effect of chitosan (CH) coating, carbon dots (CDs) and ultrasound (US) treatment on microorganisms and the physicochemical quality of fresh-cut (FC) lettuce was investigated. FC lettuces were treated by US and dipped into CD/CH coating, then packed and stored for 15 d at 4 °C. Results presented that CD/CH coating exhibited a superior effect on the depressing growth of aerobic plate count, mould and yeast, the decrease of respiratory rate, the inhibition of peroxidase and polyphenol oxidase activities, the maintenance of ascorbic acid and chlorophyll contents, the reduction of mass loss, the restriction of water distribution in US-treated FC lettuce. This exhibited that CD/CH coating effectively kept the microbial and physicochemical quality of FC lettuce.

Textural formation of instant controlled pressure drop-dried peach chips: Investigation of the electrical, thermal, and textural properties of predried peach slices with osmotic dehydration pretreatment

In this study, the effect of osmotic dehydration (OD) pretreatment with various sugar (erythritol, glucose, and trehalose) on the quality of hot-air-predried peach slices was investigated, particularly focusing on electrical properties, texture, thermal stability, and cell wall strength. Furthermore, the correlation between the properties of predried peach slices and the texture of the instant controlled pressure drop (DIC) dried peach chips was explored. OD pretreatments improved the stability and integrity of the cell wall and cell membrane of pre-dried peach slices, which inhibited the excessive expansion of samples during DIC drying. Especially, peach chips with trehalose-OD exhibited the highest crispiness (1.05 mm), the highest hardness (101.34 N) was obtained in erythritol-OD samples. Overall, the type of osmotic agents affected the texture of DIC peach chips with OD pretreatments. It should be noted that trehalose is a promising osmotic agent for controlling and regulating the quality of DIC peach chips.

Effect of guar gum, gelatin, and pectin on moisture changes in freeze-dried restructured strawberry blocks

This study aimed to investigate the effects of edible gum addition on moisture changes in freeze-dried restructured strawberry blocks (FRSB), which involved five groups: the control, 1.2% guar gum, 1.2% gelatin, 1.2% pectin, and the composite group with 0.5% guar gum, 0.5% gelatin, and 0.45% pectin. The results indicated that the drying rates of the five groups of FRSB presented similar early acceleration and later deceleration trends. Moisture content in FRSB was linearly predicted by peak area of low field nuclear magnetic resonance with R2 higher than 0.90 for all the five groups. The FRSB samples in the gelatin and composition groups formed a denser porous structure and had a lower hygroscopicity after four days of storage. This study provides a theoretical basis for controlling the processing of FRSB.

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.

Properties of co-gel between Tenebrio Molitor larvae protein and myofibrillar protein induced by transglutaminase

This study explored the effect of adding transglutaminase (TGase) to a co-gel of Tenebrio Molitor larvae protein (TMLP) and myofibrillar protein (MP). Different concentrations of TGase (0-90 U/g) were added to the co-gel. The results showed that 60 U/g TGase treatment significantly improved the gel strength and water holding capacity (WHC) by 26.51 g and 9.2 %, respectively. TGase promoted the rheological properties and accelerated the three-dimensional network structure of the co-gel. Moreover, TGase significantly increased (P < 0.05) the tyrosine residues, tryptophan residues content and hydrophobic interactions of the aliphatic groups. The chemical forces between the protein molecules changed. TGase promoted the transition of α-helix to β-sheet and free water to immobilized water, thereby improving the WHC of co-gel. The principal component analysis reflected the links among indicators. This study illustrated that TGase might be an effective strategy to improve the co-gel of TMLP and MP and emulsified meat products with insects.

Ultra-high pressure treatment improve the content of characteristic aromatic components of melon juice from the view of physical changes

Introduction

The effectiveness of ultra-high pressure (UHP) technology in retaining the flavor of fresh fruit and vegetable juices has been acknowledged in recent years. Along with previously hypothesized conclusions, the improvement in melon juice flavor may be linked to the reduction of its surface tension through UHP.

Methods

In this paper, the particle size, free-water percentage, and related thermodynamic parameters of melon juice were evaluated in a physical point for a deeper insight.

Results

The results showed that the UHP treatment of P2-2 (200 MPa for 20 min) raised the free water percentage by 7,000 times than the other treatments and both the melting enthalpy, binding constant and Gibbs free energy of P2-2 were minimized. This significantly increased the volatility of characteristic aromatic compounds in melon juice, resulting in a 1.2-5 times increase in the content of aromatic compounds in the gas phase of the P2-2 group compared to fresh melon juice.

Low-field, not low quality: 1D simplification, selective detection, and heteronuclear 2D experiments for improving low-field NMR spectroscopy of environmental and biological samples

Understanding environmental change is challenging and requires molecular-level tools to explain the physicochemical phenomena behind complex processes. Nuclear magnetic resonance (NMR) spectroscopy is a key tool that provides information on both molecular structures and interactions but is underutilized in environmental research because standard "high-field" NMR is financially and physically inaccessible for many and can be overwhelming to those outside of disciplines that routinely use NMR. "Low-field" NMR is an accessible alternative but has reduced sensitivity and increased spectral overlap, which is especially problematic for natural, heterogeneous samples. Therefore, the goal of this study is to investigate and apply innovative experiments that could minimize these challenges and improve low-field NMR analysis of environmental and biological samples. Spectral simplification (JRES, PSYCHE, singlet-only, multiple quantum filters), selective detection (GEMSTONE, DREAMTIME), and heteronuclear (reverse and CH3/CH2/CH-only HSQCs) NMR experiments are tested on samples of increasing complexity (amino acids, spruce resin, and intact water fleas) at-high field (500 MHz) and at low-field (80 MHz). A novel experiment called Doubly Selective HSQC is also introduced, wherein 1H signals are selectively detected based on the 1H and 13C chemical shifts of 1H-13C J-coupled pairs. The most promising approaches identified are the selective techniques (namely for monitoring), and the reverse and CH3-only HSQCs. Findings ultimately demonstrate that low-field NMR holds great potential for biological and environmental research. The multitude of NMR experiments available makes NMR tailorable to nearly any research need, and low-field NMR is therefore anticipated to become a valuable and widely used analytical tool moving forward.

The Cryoprotective Effect of an Antifreeze Collagen Peptide Complex Obtained by Enzymatic Glycosylation on Tilapia

Antifreeze peptides have become effective antifreeze agents for frozen products, but their low quantity of active ingredients and high cost limit large-scale application. This study used the glycosylation of fish collagen peptides with glucosamine hydrochloride catalyzed by transglutaminase to obtain a transglutaminase-catalyzed glycosylation product (TGP) and investigate its antifreeze effect on tilapia. Compared with the blank group, the freshness (pH value of 6.31, TVB-N value of 21.7 mg/100 g, whiteness of 46.28), textural properties (especially hardness and elasticity), and rheological properties of the TGP groups were significantly improved. In addition, the protein structures of the samples were investigated using UV absorption and fluorescence spectroscopy. The results showed that the tertiary structure of the TGP groups changed to form a dense polymer. Therefore, this approach can reduce the denaturation and decomposition of muscle fibers and proteins in fish meat more effectively and has a better protective effect on muscle structure and protein aggregation, improving the stability of fish meat. This study reveals an innovative method for generating antifreeze peptides by enzymatic glycosylation, and glycosylated fish collagen peptide products can be used as new and effective green antifreeze agents in frozen foods.

Intelligent Rapid Detection Techniques for Low-Content Components in Fruits and Vegetables: A Comprehensive Review

Fruits and vegetables are an important part of our daily diet and contain low-content components that are crucial for our health. Detecting these components accurately is of paramount significance. However, traditional detection methods face challenges such as complex sample processing, slow detection speed, and the need for highly skilled operators. These limitations fail to meet the growing demand for intelligent and rapid detection of low-content components in fruits and vegetables. In recent years, significant progress has been made in intelligent rapid detection technology, particularly in detecting high-content components in fruits and vegetables. However, the accurate detection of low-content components remains a challenge and has gained considerable attention in current research. This review paper aims to explore and analyze several intelligent rapid detection techniques that have been extensively studied for this purpose. These techniques include near-infrared spectroscopy, Raman spectroscopy, laser-induced breakdown spectroscopy, and terahertz spectroscopy, among others. This paper provides detailed reports and analyses of the application of these methods in detecting low-content components. Furthermore, it offers a prospective exploration of their future development in this field. The goal is to contribute to the enhancement and widespread adoption of technology for detecting low-content components in fruits and vegetables. It is expected that this review will serve as a valuable reference for researchers and practitioners in this area.

Synergistic mechanism of steam blanching and freezing conditions on the texture of frozen yellow peaches based on macroscopic and microscopic properties

Freezing and blanching are essential processing steps in the production of frozen yellow peaches, inevitably leading to texture softening of the fruit. In this study, the synergistic mechanism of stem blanching, freezing conditions (-20°C, -40°C, -80°C, and liquid nitrogen [-173°C]), and sample sizes (cubes, slices, and half peaches) on macroscopic properties of texture, cellular structure, and ice crystal size distribution of frozen yellow peaches were measured. Blanching enhanced the heat and mass transfer rates in the subsequent freezing process. For nonblanched samples, cell membrane integrity was lost at any freezing rate, causing a significant reduction in textural quality. Slow freezing further exacerbated the texture softening, while the ultra-rapid freezing caused structural rupture. For blanched samples, the half peaches softened the most. The water holding capacity and fracture stress were not significantly affected by changes in freezing rate, although the ice crystal size distribution was more susceptible to the freezing rate. Peach cubes that had undergone blanching and rapid freezing (-80°C) experienced 4% less drip loss than nonblanched samples. However, blanching softened yellow peaches more than any freezing conditions. The implementation of uniform and shorter duration blanching, along with rapid freezing, has been proven to be more effective in preserving the texture of frozen yellow peaches. Optimization of the blanching process may be more important than increasing the freezing rate to improve the textural quality of frozen yellow peaches.

Moisturizing and aroma-enhancing effects of low molecular weight fenugreek polysaccharides in cigarettes

Polysaccharides possess excellent moisturizing effects due to their abundance of hydrophilic groups and film-forming properties. Additionally, they can produce a refreshing aroma during the pyrolysis process. However, there is scarce research on their application in the tobacco field. Herein, we investigated the effects of low molecular weight fenugreek polysaccharide (FP) obtained through ethanol fractionation and DEAE-52 cellulose column chromatography on moisture retention and aroma enhancement in tobacco. The moisture retention test revealed that the addition of FP increased the moisture retention index (MRI) of tobacco by 11.72 %-16.69 %, indicating that the hydrophilic nature of polysaccharides facilitated the migration of free water in tobacco to bound water, resulting in reduced water activity. Moreover, the contact angle between polysaccharide and tobacco was <90°, enabling better infiltration into tobacco and slowing down tobacco shrinkage caused by water loss. Among all the components, EFP-20 and EFP-40 demonstrated superior performance. Furthermore, FP exhibited excellent thermal stability below 200 °C and can decomposed to produce aromatic substances at high temperatures. It also demonstrated the ability to adsorb ethyl heptanoate and thermally decompose to produce a substantial amount of heptanoic acid. Consequently, the incorporation of FP in tobacco demonstrated favorable effects on both moisturization and aroma enhancement.

Effect of blanching and ultrasound pretreatment on moisture migration, uniformity, and quality attributes of dried cantaloupe

To overcome problems of browning and crusting during the pretreatment process and provide theoretical guidance for cantaloupe convection drying at 80°C, the effects of blanching (BL) and ultrasonic (US) treatments were examined. The effects of various BL (5, 10, and 15 s) and US (10, 20, 30, and 40 min) durations on convection drying were tested. The moisture ratio, drying rate, moisture effective diffusivity, color, browning, nuclear magnetic resonance characteristics, and texture were assessed. Compared with the control group, the maximal decreases in the drying time of BL and US pretreatment groups were 40% and 33.3%, respectively. BL and US pretreatments significantly increased the effective diffusion coefficient and shortened the drying time because of the destruction of the cell structure. Low-field nuclear magnetic resonance analysis showed that free water is mainly lost during the initial drying stage, while solidified water is mainly lost during middle and late stages. According to the results of magnetic resonance imaging, the moisture distribution shows that cavitation from US acts on internal tissue, while BL disrupts the structure of external tissue. Texture data define the area enclosed by S_C-D as uniform. After BL and US pretreatment, the hardness of dried cantaloupe decreased and the uniformity increased significantly. The best pretreatment process for cantaloupe at 80°C was 10 min of US. These findings provide a reference for testing in the industrial production of dried cantaloupe and are deeply relevant for practice.

Drying Process of HPMC-Based Hard Capsules: Visual Experiment and Mathematical Modeling

Using plant-based polysaccharide gels to produce hard capsules is a novel application of this technology in the medicinal field, which has garnered significant attention. However, the current manufacturing technology, particularly the drying process, limits its industrialization. The work herein employed an advanced measuring technique and a modified mathematical model to get more insight into the drying process of the capsule. Low field magnetic resonance imaging (LF-MRI) technique is adopted to reveal the distribution of moisture content in the capsule during drying. Furthermore, a modified mathematical model is developed by considering the dynamic variation of the effective moisture diffusivity (D_eff) according to Fick's second law, which enables accurate prediction of the moisture content of the capsule with a prediction accuracy of ±15%. The predicted D_eff ranges from 3 × 10^-10 to 7 × 10^-10 m²·s^-1, which has an irregular variation with a time extension. Moreover, as temperature increases or relative humidity decreases, there is an increased acceleration of moisture diffusion. The work provides a fundamental understanding of the drying process of the plant-based polysaccharide gel, which is crucial for enhancing the industrial preparation of the HPMC-based hard capsules.

Anti-hardening effect and mechanism of silkworm sericin peptide in high protein nutrition bars during early storage

Hardening presents an inevitable challenge during the storage of high protein nutrition bars. Sericin peptide is the product of hydrolysis of sericin, a protein from the silkworm cocoon. Here in, the effects of sericin peptide addition on the hardening of high protein nutrition bars during 72 h of storage were investigated. The addition of sericin peptide to high protein nutrition bars reduced the hardening of the sample during the early storage, The main mechanism was to improve the mobility of water and small hydrophilic molecules, which slowed down the phase separation. As well, after sericin peptide addition, the ζ- potential, the content of secondary structure, and the surface hydrophobicity of the samples were also changed, which prevented the self-aggregation of proteins. These results indicate that SRP can be used as a promising anti-hardening ingredient in the food industry to improve the texture of food products.

Nondestructive detection of water status and distribution in corn kernels during hot air drying using multispectral imaging

BACKGROUND

The characteristics of corn kernels are strongly connected with the content of three statuses of water: bound water, immobilized water, and free water. Monitoring different water contents is very important to optimize the drying process, improve corn quality, and reduce energy consumption. The feasibility of nondestructive detection of water status and its distribution in corn kernels during the hot-air drying process using multispectral imaging was investigated.

RESULTS

The chemometric methods used to develop prediction models were back propagation neural network, least-squares support vector machine, and partial least squares. The back propagation neural network achieved the best prediction performance for total and free water contents, with correlation coefficient of prediction (R_p ) of 0.9717 and 0.9782 respectively, root-mean-square error of prediction (RMSEP) of 4.48% and 2.54% respectively, and ratio of prediction to deviation (RPD) of 4.87 and 4.29 respectively. And partial least squares was better for the prediction of immobilized and bound water contents, with R_p of 0.9612 and 0.9798 respectively, RMSEP of 0.57% and 0.06% respectively, and RPD of 4.78 and 4.42 respectively.

CONCLUSION

It could be concluded that multispectral imaging combined with chemometric methods would be a promising technique for rapid and nondestructive detection of water status and its distribution in corn kernels. © 2023 Society of Chemical Industry.

Moisture Property and Thermal Behavior of Two Novel Synthesized Polyol Pyrrole Esters in Tobacco

To overcome the shortcomings of high relative humidity and harmful oxidation products from traditional humectants, excellent humectants and flavor precursors were reported herein. Glucosamine hydrochloride was used as the starting material for the cyclization, oxidation, and alkylation processes that produced pyrrole acid. Then, esterification occurred with polyol catalyzed by EDC and DMAP to give the target compounds 2-(2,3-dihydroxypropyl) 4-methyl 5-methyl-1-propyl-1H-pyrrole-2,4-dicarboxylate (Gpe) and (2-hydroxypropyl) 4-methyl 5-methyl-1-propyl-1H-pyrrole-2,4-dicarboxylate (Ppe). Nuclear magnetic resonance (¹H NMR, ¹³C NMR), infrared spectroscopy (IR), and high-resolution mass recorded spectrometry (HRMS) were used to confirm the two novel polyol pyrrole ester compounds. When Gpe and Ppe were added to the tobacco shred, low-field nuclear magnetic resonance (LF-NMR) imaging was applied to assess the hygroscopicity and moisturizing capacity. Furthermore, thermogravimetry (TG) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) techniques were applied to study their thermal behaviors. These results showed that the target compounds (Gpe and Ppe) are good humectants with thermal properties of high-temperature stability and flavor release.

Characterization of Potato Tuber Tissues Using Spatialized MRI T2 Relaxometry

Magnetic Resonance Imaging is a powerful non-destructive tool in the study of plant tissues. For potato tubers, it greatly assists the study of tissue defects and tissue evolution during storage. This paper describes the MRI analysis of potato tubers with internal defects in their flesh tissue at eight sampling dates from 14 to 33 weeks after harvest. Spatialized multi-exponential T2 relaxometry was used to generate bi-exponential T2 maps, coupled with a classification scheme to identify the different T2 homogeneous zones within the tubers. Six classes with statistically different relaxation parameters were identified at each sampling date, allowing the defects and the pith and cortex tissues to be detected. A further distinction could be made between three constitutive elements within the flesh, revealing the heterogeneity of this particular tissue. Relaxation parameters for each class and their evolution during storage were successfully analyzed. The work demonstrated the value of MRI for detailed non-invasive plant tissue characterization.

Effect of osmotic dehydration with different osmosis agents on water status, texture properties, sugars, and total carotenoid of dehydrated yellow peach slices

The water status, texture properties, sugars, and total carotenoid of dehydrated yellow peach slices pretreated with or without osmotic dehydration (OD) combined with heat pump drying were studied. In this study, different osmotic agents were used, namely, sucrose and isomaltooligosaccharide (IMO) with 30 °Brix for 1, 3, and 5 h. Results showed that the dehydrated samples pretreated by sucrose-OD with the best shape and cell structure showed lower hardness compared to the dehydrated yellow peach slices with IMO-OD pretreatment and without OD pretreatment. Notably, the highest total carotenoid content was found in dehydrated yellow peach slices pretreated by IMO-OD, followed by samples without OD, and samples with sucrose-OD pretreatment. In addition, the lowest a_W (0.517) was obtained in samples with IMO-OD for 5 h, which was beneficial for storage. The assessment of water status and total carotenoid content of dehydrated yellow peach slices showed that IMO-OD pretreatment could better improve the quality of dehydrated fruits. Moreover, the use of IMO in OD treatment was a good alternative to sucrose.

Effects of tea branch liquid smoke on oxidation and structure of myofibrillar protein derived from pork tenderloin during curing

This study focused on how different concentrations of tea branch liquid smoke (TLS) in the curing solution impacted the physicochemical properties and antioxidant properties of pork tenderloin. Five experimental (1.25 mL/kg, 2.5 mL/kg, 5 mL/kg, 10 mL/kg, 20 mL/kg) and blank groups set up over 4 days, and it was found that the physicochemical indexes, antioxidant capacity, thermal stability and protein network structure of the cured meat using 5 mL/kg of liquid smoke were excellent than the other groups used (P < 0.05). However, concentrations at 20 mL/kg accelerated protein oxidation. Low frequency nuclear magnetic resonance (LFNHR) revealed that TLS also improved the water holding capacity of the cured meat by increasing the percentage of bound water. Additionally, the correlation analysis demonstrated that the inoxidizability of myofibrillar protein was significantly related to cooking loss and water distribution, which were adjusted by changing the usage of liquid smoke.

Cactus polysaccharides enhance preservative effects of ultrasound treatment on fresh-cut potatoes

The shelf life of fresh-cut fruits and vegetables is affected by microbial growth, enzymatic browning, and loss of flavor. Although ultrasound (US) treatment is often used in the preservation of fresh-cut fruits and vegetables, it has limited antibacterial and preservative effects. Here, we used cactus polysaccharides (CP) to enhance the preservative effect of ultrasound treatment and extended the shelf life of fresh-cut potatoes. The results showed that combined treatment (CP + US) exerted better antimicrobial and anti-browning effects than individual treatments (either US or CP alone). In addition, CP + US has no adverse effect on texture and quality properties, as well as reduced the mobility of internal water. Combination treatment not only significantly decreased the activities of polyphenol oxidase and peroxidase (P < 0.05), but also maintained a high level of phenylalanine ammonia lyase activity and total phenol content during storage. It also maintained the integrity of cell membrane and reduced its permeability by inhibiting the peroxidation of membrane lipids. In addition, CP + US treatment significantly inhibited the activity of antioxidant enzymes and maintained a high DPPH scavenging ability. GC-IMS technology was used to evaluate the flavor of fresh-cut potatoes. The results showed that CP + US treatment reduced the production of a peculiar smell during storage and maintained a good flavor by inhibiting the production of aldehydes. Taken together, these results indicate that the effective preservation method of CP + US treatment can be utilized to increase the shelf life of fresh-cut potatoes.

Recent application of artificial neural network in microwave drying of foods: a mini-review

The microwave-assisted thermal process is a high-efficiency drying method and is promising to be applied in the food industry. However, the prediction of the thermal treatment results from such a dynamic and complicated process can be difficult. Additionally, the determination of the optimal drying parameters, such as drying temperature, microwave power, and drying time for optimized performance can also be hard. Recently, extensive research has been focusing on the use of artificial neural network (ANN) models in the laboratory-scale microwave drying processes and has shown the feasibility of such application. As a regression tool, the ANN models have been widely used in predicting drying performance; when integrated with additional optimizing algorithms, the ANN models could be used for drying parameter optimization; and when combined with real-time measuring techniques (e.g. nuclear magnetic resonance), the ANN models could be used for monitoring and controlling the drying process in a dynamic sense. Future research could focus on testing the developed ANN models in industrial-scale microwave drying processes and applying the ANN models in microwave drying kinetics research for optimizing the dynamic drying processes. © 2022 Society of Chemical Industry.

Intelligent detection for fresh-cut fruit and vegetable processing: Imaging technology

Fresh-cut fruits and vegetables are healthy and convenient ready-to-eat foods, and the final quality is related to the raw materials and each step of the cutting unit. It is necessary to integrate suitable intelligent detection technologies into the production chain so as to inspect each operation to ensure high product quality. In this paper, several imaging technologies that can be applied online to the processing of fresh-cut products are reviewed, including: multispectral/hyperspectral imaging (M/HSI), fluorescence imaging (FI), X-ray imaging (XRI), ultrasonic imaging, thermal imaging (TI), magnetic resonance imaging (MRI), terahertz imaging, and microwave imaging (MWI). The principles, advantages, and limitations of these imaging technologies are critically summarized. The potential applications of these technologies in online quality control and detection during the fresh-cut processing are comprehensively discussed, including quality of raw materials, contamination of cutting equipment, foreign bodies mixed in the processing, browning and microorganisms of the cutting surface, quality/shelf-life evaluation, and so on. Finally, the challenges and future application prospects of imaging technology in industrialization are presented.

Effect of subfreezing storage on the qualities of dough and bread containing pea protein

BACKGROUND

In this paper, -6, -9 and -12 °C were selected as subfreezing temperatures of dough containing pea protein based on the results of low-field nuclear magnetic relaxation time. The effect of storage at subfreezing temperatures on dough properties was then investigated and compared with sample storage at -18 °C.

RESULTS

The pH value, springiness, resilience, cohesiveness of dough and sensory score of bread gradually decreased and the hardness and water loss rate of dough gradually increased with the extension of storage time. However, dough hardness, viscoelasticity and fermentation volume were maintained more effectively in subfreezing storage than in -18 °C storage. The subfreezing temperature could alleviate the damage of gluten network structure in frozen dough by ice crystals and was beneficial in maintaining the elasticity of gluten proteins. The network system of pea protein, gluten protein and starch granules in dough storage at -9 and -12 °C was more tightly connected and the microstructure was similar to that at -18 °C. There was no significant difference between the quality of bread made from the dough stored at subfreezing temperature and that stored at -18 °C for 1-6 weeks, and the preservation effect at -12 °C was closer to that at -18 °C.

CONCLUSION

Subfreezing storage can keep the stability of dough containing pea protein close to traditional frozen storage (-18 °C), which provides a new method for storage and transportation of frozen dough. © 2022 Society of Chemical Industry.

Visual Monitoring of Disintegration of Solid Oral Dosage Forms in Simulated Gastric Fluids Using Low-Field NMR Imaging

Compared to traditional drug release monitoring with manual sampling and testing procedures, low-field nuclear magnetic resonance (LF-NMR) imaging is a one-step, visual, non-destructive, and non-invasive measurement method. Here, we reported the application of LF-NMR to image the morphology, component, sub-diffusion, and spatial distribution of a solid oral formulation, Biyankang tablets, during dissolution in vitro. The drug ingredients with characteristic relaxation times were distinguished and localized based on the signal of standards, such as patchouli oil, Xanthium strumarium extract, and starch. The hydration, swelling, disintegration, and sub-diffusion of tablets in simulated gastric fluids (SGF) were visualized statically. All tablets showed similar expansion (37.4-42.0%) along the direction of thickness at 25 min and reached a full disintegration at 145 min, at pH 1.80-6.15, indicating pH-independent swelling and disintegration. Compared to that static immersion within 20 mL SGF, the tablet disintegration time was shortened by ~ 11% in 30 mL SGF. The application of shear reduced the time by ~ 28%, suggesting a major role of hydrodynamic condition in tablet dissolution. The ability to simultaneously visualize, distinguish, and localize drug ingredients using LF-NMR is expected to provide valuable information to develop drug release monitoring systems in vitro and potentially in vivo using small animal studies.

Visualization and quantification of content and hydrogen bonding state of water in apple and potato cells by confocal Raman microscopy: A comparison study

Water is the most abundant component in fresh fruit and vegetables and its distribution and hydrogen bonding state in cells has a significant influence on food processing. In the current study, an improved method based on our earlier studies was developed to directly visualize the spatial distribution of content and hydrogen bonding state of water in apple and potato cells for the first time and the difference in water distribution in these cells was compared. Additionally, based on the distribution images of content and hydrogen bonding state of water in different regions in apple and potato tissues, the total water and free water contents, and the hydrogen bonding state of free water were quantified and compared with those obtained by nuclear magnetic resonance and Marinchik methods, demonstrating that the method could be successfully used for quantifying the content and hydrogen bonding state of water in fruit and vegetable cells.

Investigation on the rehydration mechanism of freeze-dried and hot-air dried shiitake mushrooms from pores and cell wall fibrous material

Shiitake mushrooms are unique in their porous structure, which could be affected by various chemical/physical changes during freeze-drying process. In this work, rehydration characteristics of freeze-dried products which were pre-frozen at -20 ℃, -40 ℃, -80 ℃, and -196 ℃ (by liquid nitrogen) were explored from aspects of pores and cell wall fibrous material. Although the appearance and rehydration rate of freeze-dried samples was better than hot-air dried samples with drying temperature ranging from 30 ℃ to 90 ℃, the final rehydration ratio was still less than hot-air dried samples dried at low temperature (30 ℃ and 40 ℃) due to the more serious structural damage by freeze-drying. Hydration capacity of the cell wall fiber was increased by freeze-drying, which might be ascribed to the loosen structure of cell wall instead of composition changes. Thus, hot-air drying at low temperature is still recommend and freeze-drying should be further optimized.

Quantitative MRI analysis of structural changes in tomato tissues resulting from dehydration

A quantitative magnetic resonance imaging (MRI) analysis at 1.5T of the effects of different dehydration regimes on transverse relaxation parameters measured in tomato tissue is presented. Multi-exponential T₂ maps have been estimated for the first time, providing access to spatialized microstructural information at voxel scale. The objective was to provide a better understanding of the changes in the multi-exponential transverse relaxation parameters induced by dehydration in tomato tissues and to unravel the effects of microstructure and composition on relaxation parameters. The results led to the hypothesis that the multi-exponential relaxation signal reflects cell compartmentation and tissue heterogeneity, even at the voxel scale. Multi-exponential relaxation times provided information about water loss from specific cell compartments and seem to indicate that the dehydration process mainly affects large cells. By contrast, total signal intensity showed no sensitivity to variations in water content in the range investigated in the present study (between 95% [fresh tissue] and 90% [after dehydration]). The variation in relaxation times resulting from water loss was due to both changes in solute concentration and compartment size. The comparative analysis of the two contrasted tissues in terms of microporosity demonstrated that magnetic susceptibility effects, caused by the presence of air in the placenta tissue, significantly impact the effective relaxation and might be the dominant effect in the variations observed in relaxation times in this tissue.

Two-step diffusion in cellular hygroscopic (vascular plant-like) materials

Vascular plants, a vast group including conifers, flowering plants, etc., are made of a cellular hygroscopic structure containing water in the form of either free (i.e., in a standard liquid state) or bound (i.e., absorbed in the cell walls) water. From nuclear magnetic resonance techniques, we distinguish the dynamics of bound water and free water in a typical material (softwood) with such a structure, under convective drying. We show that water extraction relies on two mechanisms of diffusion in two contiguous regions of the sample, in which respectively the material still contains free water or only contains bound water. However, in any case, the transport is ensured by bound water. This makes it possible to prolong free water storage despite dry external conditions and shows that it is possible to extract free water in depth (or from large heights) without continuity of the free water network.

Effects of Enzymatic Konjac Glucomannan Hydrolysates on Textural Properties, Microstructure, and Water Distribution of Grass Carp Surimi Gels

This present work investigated the influence of konjac glucomannan (KGM) enzymatic hydrolysates on the textural properties, microstructure, and water distribution of surimi gel from grass carp (Ctenopharyngodon idellus). The molecular weight (M_w) of KGM enzymatic hydrolyzed by β-dextranase degraded from 149.03 kDa to 36.84 kDa with increasing enzymatic time. In the microstructure of surimi gels, KGM enzymatic hydrolysates with higher M_w showed entangled rigid-chains, while KGM enzymatic hydrolysates with lower M_w (36.84 kDa) exhibited swelled fragments. The hardness of surimi gel with a decline in KGM M_w exhibited first increasing then decreasing trends, while the whiteness of surimi gel increased. When KGM M_w decreased, the immobile water percentage of total signals decreased from 96.7% to 93.6%, and mobile water increased from 3.03% to 6.37%. In particular, the surimi gel with the addition of K2 showed better gel strength and water distributions. KGM enzymatic hydrolysates are expected to be used as a low-calorie healthy gel enhancer in surimi processing.

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

Effects of blanching (BL), ultrasound (US) and freeze-thawing (FT) pretreatments prior to far-infrared drying (FIRD) on drying characteristics, water distribution, and quality parameters of seed-used pumpkin (SUP) slices were investigated in this study. US, BL and FT pretreatments significantly accelerated drying rate due to the destruction of cell structure. Modified Page model was the fittest model for predicting the FIRD process. Low field nuclear magnetic resonance (LF-NMR) results revealed that T₂ distribution curves of all pretreated samples moved rapidly to the positive x-axis direction, indicating an increase in the rate of water migration. The color of US-FIRD was closer to fresh SUP. BL-FIRD exhibited the highest free polyphenols content (241.28 ± 1.11 mg GAE/100 g DW) and total carotenoids content (129.69 ± 2.49 μg/ g DW), increasing by 45% and 34% respectively compared to the untreated sample.

Influence of sequential exogenous pretreatment and contact ultrasound-assisted air drying on the metabolic pathway of glucoraphanin in broccoli florets

In this investigation, the combinations of exogenous pretreatment (melatonin or vitamin C) and contact ultrasound-assisted air drying were utilized to dry broccoli florets. To understand the influences of the studied dehydration methods on the conversion of glucoraphanin to bioactive sulforaphane in broccoli, various components (like glucoraphanin, sulforaphane, myrosinase, etc.) and factors (temperature and moisture) involved in the metabolism pathway were analyzed. The results showed that compared with direct air drying, the sequential exogenous pretreatment and contact ultrasound drying shortened the drying time by 19.0-22.7%. Meanwhile, contact sonication could promote the degradation of glucoraphanin. Both melatonin pretreatment and vitamin C pretreatment showed protective effects on the sulforaphane content and myrosinase activity during the subsequent drying process. At the end of drying, the sulforaphane content in samples dehydrated by the sequential melatonin (or vitamin C) pretreatment and ultrasound-intensified drying was 14.4% (or 26.5%) higher than only air-dried samples. The correlation analysis revealed that the exogenous pretreatment or ultrasound could affect the enzymatic degradation of glucoraphanin and the generation of sulforaphane through weakening the connections of sulforaphane-myrosinase, sulforaphane-VC, and VC-myrosinase. Overall, the reported results can enrich the biochemistry knowledge about the transformation of glucoraphanin to sulforaphane in cruciferous vegetables during drying, and the combined VC/melatonin pretreatment and ultrasound drying is conducive to protect bioactive sulforaphane in dehydrated broccoli.

Evaluation of quality change in Salviae miltiorrhizae radix et rhizoma during drying by LF-NMR and HPLC

Salviae miltiorrhizae radix et rhizoma (Danshen, in Chinese) is one of the traditional Chinese medicines commonly used in clinical practice. In this study, low field nuclear magnetic resonance (LF-NMR) was used to detect changes in the moisture content during the drying of Danshen. Three water states (bound, immobilized, and free) in Danshen were investigated by multi-exponential fitting of the NMR data. Mass changes during drying were analyzed using high-performance liquid chromatography and partial least squares discriminant analysis. The results revealed that two components, salvianolic acid B and tanshinone, were the main chemical substances that produced the differences. Correlations were found among chemical substances, color, and moisture. LF-NMR can quickly assess the moisture content during drying. It also provides a practical tool for the production and processing of medicines or slices.

Effects of ultrasound pretreatment on the drying kinetics, water status and distribution in scallop adductors during heat pump drying

BACKGROUND

A material's physical and chemical properties during drying are influenced by water status and distribution. However, merely overall water removal is reported in many investigations, which hinders clarification of the drying mechanism. Therefore, the effects of ultrasound (US) pretreatment (0 W, CK; 90 W, US-90; 180 W, US-180) on the drying kinetics and quality of heat pump drying (HPD) scallop adductors was performed based on low-field nuclear magnetic resonance (LF-NMR).

RESULTS

Compared with CK, effective moisture diffusion coefficient was increased by 12.43% and 23.35% for US-90 and US-180, respectively. The Weibull model satisfactorily described the drying characteristics with a high r² (> 0.998), low rmse (< 0.0120) and χ² (< 0.00008). LF-NMR revealed that the immobilized water was predominant in scallop adductors. As drying proceeded, the relaxation time of free and immobilized water was decreased sharply, whereas the relaxation time of bound water scarcely changed. The time required to reduce approximately two-fifths of the original peak area of immobilized water was 720, 630 and 540 min for CK, US-90 and US-180, respectively. The amplitude of immobilized water was decreased and bound water increased significantly, although free water was kept constant (ranging 1-2%). US pretreatment reduced total color difference and hardness, but enhanced the toughness of dried scallop adductors. However, US had no significant influence on the product rehydration rate and shrinkage rate.

CONCLUSION

LF-NMR was successfully employed to evaluate the drying degree of scallop adductors. US facilitated the conversion of immobilized water to free water and, consequently, promoted water removal during HPD. © 2021 Society of Chemical Industry.