Effect of microwave blanching on antioxidant activity, phenolic compounds and browning behaviour of some fruit peelings

Effects of delayed tuber cutting after catalytic infrared heat treatment on browning of fresh-cut potatoes and its potential mechanisms

Heat treatment, a form of thermal stress can confer anti-browning properties to potato tubers. However, the effect of delayed cutting after catalytic infrared heat treatment (DC-CIRHT) on browning inhibition remains unexplored. The study optimized catalytic infrared heat treatment conditions (55 °C for 10 min) and delayed cutting time (3 d). DC-CIRHT significantly inhibited the increase of browning index and browning degree and did not affect the quality of potato tubers. The mechanisms underlying browning inhibition involve two aspects: the reduction of phenolic-enzyme catalysis and the enhancement of the defense system. DC-CIRHT inhibits browning by suppressing polyphenol oxidase, peroxidase and phenylalanine ammonia lyase enzyme activity, reducing total phenol and flavonoid content, enhancing antioxidant activity, reducing membrane permeability and MDA, and balancing amino acid metabolism. This method offers a novel strategy for inhibiting browning during the post-harvest storage and processing of fruits and vegetables.

Mechanisms underlying the effect of high-temperature curing treatments on the browning response of fresh-cut yams

Fresh-cut yams are prone to browning, which impacts their quality and marketability. This study evaluated the efficacy of a high-temperature curing (HTC) treatment (35 °C for 7 days) in inhibiting the postharvest browning of fresh-cut yams. Results indicated that the HTC treatment primarily mitigated browning by inhibiting key enzymes involved in phenolic oxidation, including polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL), while reducing the accumulation of total phenolics and lignin. HTC also reduced respiration rate and ethylene production, while enhancing flavonoid content. Transcriptomic and metabolomic analyses indicated that HTC inhibited the synthesis of phenolic compounds and lignin, modulated glutathione metabolism and genes involved in starch and sucrose metabolism, all contributing to browning prevention. These findings suggest that HTC functions by both directly inhibiting enzymatic browning and enhancing antioxidant defenses, providing a strategy to preserve the quality and extend the shelf life of fresh-cut yams.

Effect of cyclic vacuum-steam blanching on the quality characteristics and functional properties of Malabar spinach (Basella alba) dried by non-water infrared refractance window drying

In the present work, an effluent-free novel method including cyclic vacuum steam pulsed blanching (VSPB) pretreatment and non-water infrared refractance window drying (non-water IR-RWD) was employed to explore its effect on enzyme inactivation, drying behavior, quality and functional properties of dried Malabar spinach. The highest inactivation of peroxidase (90.23 %) and polyphenol oxidase (94.58 %) was observed in the 4th cycle of the VSPB pretreatment. With the increase in VSPB cycles from 1 to 5, the drying time was significantly reduced by 27.27 % to 54.54 % compared to the untreated sample. The color change values (ΔE) of VSPB pretreated non-water IR-RWD samples varied from 7.37 to 8.03. The findings in the current work indicated that vacuum-steam pulsed blanching combined with a non-water IR-RWD process is a promising technique for Malabar spinach powder production.

Chrysanthemum morifolium Ramat. as a traditional tea material: Unraveling the influence of kill-green process on drying characteristics, phytochemical compounds, and volatile profile

The dried capitulum of chrysanthemums is a traditional material in scented tea, and the kill-green process is a critical step in determining their quality. However, the changes in the physicochemical properties during kill-green and the mechanisms by which these changes affect drying characteristics, metabolic components, and aroma profiles remain unclear. Therefore, this study investigated the changes in water status, polyphenol oxidase and peroxidase activities, and microstructure during high-humidity air impingement kill-green (HHAIK) and steam kill-green (SK), and their effects on drying behavior, color, phytochemicals, and volatile profile of dried chrysanthemums. Results showed that the kill-green process increased the freedom degree of immobile water, reduced the relative content of free water, and induced microstructure alterations, thus enhancing the water diffusion and shortening the subsequent drying time by up to 46.15 %. Compared to SK, HHAIK more rapidly inactivated PPO and POD, causing an improved color profile of dried samples. Dried samples treated with HHAIK for 60 s exhibited higher retention of 9 individual phenolics, total sugar, amino acids, and volatile compounds, thus resulting in higher sensorial acceptance than those treated with SK for 60 s. This study offers theoretical insights and technical support for the future development of high-quality chrysanthemum products.

Investigating the effects of thermal processing on bitter substances in atemoya (Annona cherimola × Annona squamosa) through sensory-guided separation

Atemoya (Annona cherimola × Annona squamosa) is a specialty crop in Taiwan. Thermal treatment induces bitterness, complicating seasonal production adjustments and surplus reduction. In this research, sensory-guided separation, metabolomics, and orthogonal partial least squares discrimination analysis (OPLS-DA) are used for identifying the bitterness in atemoya which originates from catechins, epicatechin trimers, and proanthocyanidins. Different thermal treatments (65 °C, 75 °C, and 85 °C) revealed that the glucose and fructose contents in atemoya significantly decreased, while total phenols, flavonoids, and tannins significantly increased. The concentration of 5-hydroxymethylfurfural (5-HMF) increased from 23.16 ng/g in untreated samples to 400.71 ng/g (AP-65), 1208.59 ng/g (AP-75), and 2838.51 ng/g (AP-85). However, these levels are below the 5-HMF bitterness threshold of 3780 ng/g. Combining mass spectrometry analysis with sensory evaluation, OPLS-DA revealed that atemoya treated at 65 °C, 75 °C, and 85 °C exhibited significant bitterness, with the main bitter components being proanthocyanidin dimers and trimers.

Latest Advances in Green Extraction of Polyphenols from Plants, Foods and Food By-Products

Phenolic compounds present in plants and foods are receiving increasing attention for their bioactive and sensory properties, accompanied by consumers' interest in products with health benefits derived from natural rather than artificial sources. This, together with the sustainable development goals for the 21st century, has driven the development of green extraction techniques that allow obtaining these compounds with the safety and quality required to be applied in the food, cosmetic and pharmaceutical industries. Green extraction of natural products involves practices aiming at reducing the environmental impact of the preparation processes, based on using natural or less-polluting solvents, lower energetic requirements and shorter extraction times, while providing greater efficiency in the recovery of target compounds. In this article, the principles of sustainable extraction techniques and the advances produced in recent years regarding green isolation of polyphenols from plants, food and food waste are reviewed.

Study on the effects of radio frequency blanching on polyphenol oxidase activity, physicochemical properties, and microstructure of iron yam

The effects of radio frequency (RF) and hot water blanching on polyphenol oxidase (PPO) activity, physicochemical properties, and microstructure of iron yams were investigated. The heating rate of RF was the largest, and the heating uniformity was the best at the electrode gap of 160 mm and the material height of 90 mm. The residual activity of PPO was significantly reduced from 49.95% to 4.21%, whereas the RF heating temperature (65-85°C) increased (p < 0.05). The color and texture of yams treated with RF blanching were better preserved compared with those of hot water blanching at a similar degree of enzyme inactivation. The microstructure showed that these changes in physicochemical properties were caused by cellular damage. The surface cells of yams were more severely damaged than the center cells after hot water blanching at 95°C for 3 min. Moreover, the surface cells after hot water blanching also showed more damage than the cells after RF blanching. Thus, RF blanching is a technique with development potential in the food industry.

Influence of ultrasonic pretreatment on the quality attributes and pectin structure of chili peppers (Capsicum spp.)

Chili peppers (Capsicum spp.) exhibit a diverse range of quality characteristics and pectin structures, which are influenced by various factors. This study aimed to investigate the effects of ultrasound (US), ultrasonic combined hot blanching (US-BL), and ultrasonic combined freezing and thawing (US-FT) on the quality characteristics and pectin structure of vacuum pulsation-dried (VP) chili peppers. The results indicated that US-BL samples exhibited the highest L* and a* values, retained maximum capsorubin, and showed an increase in vitamin C, total phenols, and rehydration by 14.28 %, 40.87 %, and 8.66 %, respectively. In contrast, the US-FT samples exhibited the highest capsaicin and dihydrocapsaicin content, which increased by 54.97 % and 64.04 %, respectively. Pretreatment resulted in higher pectin linearity, a lower degree of branching, and a reduced molecular weight in the US-BL sample. Atomic force microscopy confirmed the degrading effect of pretreatment on the pectin structure. Pearson's correlation analysis revealed that capsorubin, capsaicin analogs, vitamin C, and total phenols were highly correlated with pectin linearity and molecular weight. This study found that US-BL was the most effective pretreatment method for improving the quality of pulsatile chili peppers and provides theoretical support for the application of VP chili peppers.

Effects of thermal processing on natural antioxidants in fruits and vegetables

Research on the content of polyphenolic compounds in fruits and vegetables, the extraction of bioactive compounds, and the study of their impact on the human body has received growing attention in recent years. This is due to the great interest in bioactive compounds and their health benefits, resulting in increased market demand for natural foods. Bioactive compounds from plants are generally categorized as natural antioxidants with health benefits such as anti-inflammatory, antioxidant, anti-diabetic, anti-carcinogenic, etc. Thermal processing has been used in the food sector for a long history. Implementing different thermal processing methods could be essential in retaining the quality of the natural antioxidant compounds in plant-based foods. A comprehensive review is presented on the effects of thermal blanching (i.e., hot water, steam, superheated steam impingement, ohmic and microwave blanching), pasteurization, and sterilization and drying technologies on natural antioxidants in fruits and vegetables.

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.

PhInd-Database on Polyphenol Content in Agri-Food By-Products and Waste: Features of the Database

Timely access to topic-relevant datasets is of paramount importance for the development of any successful strategy (food waste reduction strategy), since datasets illuminate opportunities, challenges and development paths. PhInd is the first comprehensive database on polyphenol content in plant-based by-products from the agri-food sector or the wastewater sector and was developed using peer-reviewed papers published in the period of 2015-2021. In total, >450 scientific manuscripts and >6000 compound entries were included. Database inclusion criteria were polyphenol contents = determined using HPLC/UHPLC quantitative methods. PhInd can be explored through several criteria which are either 'open' or checkboxes. Criteria are given in subsections: (a) plant source; (b) by-product industrial processing; (c) pre-treatment of by-products before the isolation of polyphenols; and (d) the extraction step of polyphenols. Database search results could be explored on the website directly or by downloading Excel files and graphs. This unique database content is beneficial to stakeholders-the food industry, academia, government and citizens.

Comparison of different drying technologies for walnut (Juglans regia L.) pellicles: Changes from phenolic composition, antioxidant activity to potential application

The analysis of the phenolic profile in the walnut pellicle (WP) and its exploitability can help to promote the valorization of the industrial waste from walnut production. Three forms of 33 monomeric phenols in WPs were quantified based on our previously established LC-MS/MS method. The levels of protocatechuic acid and 4-hydroxybenzoic acid in the WPs were the highest, exceeding 400 μg/g. Antioxidant tests revealed that all three phenolic forms of WPs were effective antioxidants (IC50: 2.12-35.05 µg/mL). The findings also revealed that drying temperature had a substantial type-dependent effect on phenolics and their antioxidant ability in WPs. KEGG enrichment analysis found that drying method has the greatest impact on WPs phenols in six metabolic pathways. Besides, 11 active substances in WPs were identified by a compound-targeted activity screening approach, indicating that WPs could be used as a natural antioxidant source in the development of medical and nutraceutical products.

Extraction-depended and thermally-modulated physical and chemical properties of powders produced from cranberry pomace extracts

Recovering bioactives from botanical by-products in the form of powders has been attempted through a number of multidirectional approaches. Yet understanding the processing of such plant formulations requires dedicated research owing to the manifold factors shaping the quality of powders. Therefore, the study aimed at production of cranberry powders from pomace extracts and to evaluate how different solvent type, carriers and drying techniques modulate their physico-chemical properties. Freeze- and vacuum drying significantly differentiated samples in terms of physical properties, while the extraction solvent and carrier type had substantial impact on chemical ones. For carrier-added products pomace extraction with acidified 50% ethanol resulted in the highest content of identified phenolics in powders (up to 5.87 g · 100 g-1 dry matter), while 30% acetone in the lowest (on average, 3.94 g · 100 g-1 dry matter). Acetone extraction strengthened the formation of hydroxymethyl-L-furfural that was higher when compared to acidified 50% ethanol, while trace amounts were reported for non-acidified counterpart. Similar observation was made in the case of flavan-3-ols. Addition of carriers during powders production led to the lower hydroxymethyl-L-furfural formation even down to 74% with regard to carrier-free samples. The study confirmed feasibility of managing cranberry pomace into high-value powders in extraction-depended and thermally-modulated quality matter.

Development of thermoultrasound assisted blanching to improve enzyme inactivation efficiency, drying characteristics, energy consumption, and physiochemical properties of sweet potatoes

Thermoultrasound (USB) as a promising alternative to traditional hot water (HWB) blanching was employed to blanch sweet potatoes and its influence on enzyme activity, drying behavior, energy consumption and physiochemical properties of sweet potatoes were investigated. Results showed that successive increases in blanching temperature and time resulted in significant (p < 0.05) decreases in PPO and POD activities. Compared to HWB, USB led to more effective drying by promoting texture softening, moisture diffusion, microstructure alterations, and microchannels formation, which significantly reduced energy consumption and improved the overall quality of the dried sample. Specifically, USB at 65 °C for 15 min improved water holding capacity and ABTS, while USB at 65 °C for 30 min improved color (more red and yellow), total phenolic content, total carotenoid content, and DPPH. Unfortunately, blanching process showed detrimental effects on the amino acid composition of dried samples. Overall, the development of thermoultrasound assisted blanching for sweet potatoes has the potential to revolutionize the processing and production of high-quality sweet potato products, while also improving the sustainability of food processing operations.

Ultrasonic-Assisted and Microwave-Assisted Extraction of Phenolics and Terpenoids from Abelmoschus sagittifolius (Kurz) Merr Roots Using Natural Deep Eutectic Solvents

This research extracted phenolics and terpenoids from Abelmoschus sagittifolius (Kurz) Merr roots using natural deep eutectic solvent-based novel extraction techniques. Twelve natural deep eutectic solvents (NADESs) were produced for recovering phenolics and terpenoids. Citric acid/glucose and lactic acid/glucose, with a molar ratio of 2:1, were determined as the most appropriate NADESs for extracting phenolics and terpenoids, respectively. Afterward, the proper conditions for NADES-based ultrasonic-assisted and microwave-assisted extraction were investigated. Then, the time and liquid-to-solid ratios of ultrasonic- and microwave-combined extraction methods and the sequence of ultrasound and microwave treatments were examined. The conditions of ultrasonic-assisted extraction were 40 mL/g liquid-to-solid ratio, 40% water content, 30°C, 5 min, and 600 W ultrasonic power for the highest terpenoid recovery at 69 ± 2 mg UA/g dw, while 150 W ultrasonic power was suitable for phenolic recovery at 9.56 ± 0.17 mg GAE/g dw. The conditions of microwave-assisted extraction were 50 mL/g liquid-to-solid ratio, 20% water content, 400 W microwave power, and 2 min to acquire the highest phenolics and terpenoids at 22.13 ± 0.75 mg GAE/g dw and 90 ± 1 mg UA/g dw, respectively. Under appropriate conditions, the biological activities, phenolic content, and terpenoid content of obtained extracts from four extraction methods, including ultrasonic-assisted, microwave-assisted, ultrasonic-microwave-assisted, and microwave-ultrasonic-assisted extraction, were compared to select the most proper method. The conditions of ultrasonic-microwave-assisted extraction were 40 mL/g liquid-to-solid ratio, 5 min sonication, and 1 min microwave irradiation to obtain the highest phenolic and terpenoid contents (27.07 ± 0.27 mg GAE/g dw and 111 ± 3 mg UA/g dw, respectively). Ultrasonic-microwave-assisted extraction showed the highest phenolic content, terpenoid content, and biological activities among the four extraction techniques. The changes in the surface morphology were determined using scanning electron microscopy. This study demonstrated that ultrasonic-microwave-assisted extraction was an effective and sustainable method in food and pharmaceutical industries for recovering phenolics and terpenoids from Abelmoschus sagittifolius (Kurz) Merr.

Effect of Microwave Treatments Combined with Hot-Air Drying on Phytochemical Profiles and Antioxidant Activities in Lily Bulbs (Lilium lancifolium)

Lily bulbs (Lilium lancifolium Thunb.) are rich in phytochemicals and have many potential biological activities which could be deep-processed for food or medicine purposes. This study investigated the effects of microwaves combined with hot-air drying on phytochemical profiles and antioxidant activities in lily bulbs. The results showed that six characteristic phytochemicals were identified in lily bulbs. They also showed that with an increase in microwave power and treatment time, regaloside A, regaloside B, regaloside E, and chlorogenic acid increased dramatically in lily bulbs. The 900 W (2 min) and the 500 W (5 min) groups could significantly suppress the browning of lily bulbs, with total color difference values of 28.97 ± 4.05 and 28.58 ± 3.31, respectively, and increase the content of detected phytochemicals. The highest oxygen radical absorbance activity was found in the 500 W, 5 min group, a 1.6-fold increase as compared with the control (57.16 ± 1.07 μmol TE/g DW), which was significantly relevant to the group's phytochemical composition. Microwaves enhanced the phytochemicals and antioxidant capacity of lily bulbs, which could be an efficient and environmentally friendly strategy for improving the nutrition quality of lily bulbs during dehydration processing.

Modified Erchen decoction ameliorates cognitive dysfunction in vascular dementia rats via inhibiting JAK2/STAT3 and JNK/BAX signaling pathways

BACKGROUND

Vascular dementia (VaD) is one of the most common clinical syndromes of progressive neurocognitive dysfunction with uncertain mechanisms. Modified Erchen decoction (MECD), developed from "Erchen decoction (ECD)" recorded in "Taiping Huimin Heji Jufang", showed a good effect in the treatment of VaD. However, its therapeutic mechanism is still unclear.

PURPOSE

This study aimed to elucidate the multi-target mechanisms of MECD against VaD in vivo and in vitro.

METHODS

VaD model was established by two-vessel obstruction (2-VO) in Sprague-Dawley rats. Six groups, including the control, 2-VO operation, MECD treatment (2.5, 5.0 and 10.0 g kg^-1 d^-1), donepezil hydrochloride (positive control, 0.45 g kg^-1 d^-1) were designed in the whole experiment. After oral administration for 4 weeks, the effects of MECD were verified by behavioral experiments, histological observation, and biochemical index analysis. The chemical profiling of MECD was performed by UHPLC-Orbitrap Fusion-HRMS, and a "compound-target-pathway" multivariate network was constructed to validate and elucidate its pharmacological mechanisms.

RESULTS

Compared with 2-VO group, MECD treatment significantly alleviated anxiety and improved spatial memory in VaD rats according to the open field test (OFT) and Y-maze test. A significant increase in neuron number was observed from hematoxylin and eosin (H&E) stained images in cornu ammonis 1 (CA1) of the hippocampal region after MECD treatment. On the one hand, MECD reduced the plasma levels of triglyceride (TG), low-density lipoprotein (LDL), malondialdehyde (MDA), and amyloid-beta 42 (Aβ42), and inhibited mRNA expression of interleukin-1 beta (Il-1β) and Il-6 in the hippocampus. On the other hand, superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) were significantly increased after treatment with MECD. Moreover, MECD reduced the mRNA expression and protein expression of janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), c-Jun N-terminal kinase (JNK), and BCL2-associated X (BAX) in the brain of 2-VO rats. Furthermore, 71 compounds were identified from the extract of MECD. Among them, liquiritin and isochlorogenic acid C gave inhibiting effects on the mRNA expression of Jnk. In addition, liquiritin and hesperetin were conformed with the inhibition of Jak2 transcription level in vitro experiments.

CONCLUSION

MECD has demonstrated a significant amelioration effect on cognitive dysfunction in VaD rats via JAK2/STAT3 and JNK/BAX signaling pathways, which represents an innovative insight into the "activate blood and eliminate phlegm" theory.

The influence of conventional and novel blanching methods on potato granules, phytochemicals, and thermal properties of colored varieties

Introduction

Colored potatoes comprise many bioactive compounds that potentially support human health. Polyphenols present in them have associated therapeutic benefits like antimutagenic and anticarcinogenic properties.

Method

The current study aimed to explore the effects of different blanching methods (steam blanching, hot water blanching, and microwave-assisted blanching) on the phytochemical and structural aspects of PP-1901 and Lady Rosetta (LR) potato varieties. Changes in the antioxidant activity, color, total ascorbic acid, phenolic, and flavonoid content were based on the variations in parameters including temperature (blanching using hot water and steam) and capacity 100- 900 W (blanching using microwave).

Results

For both PP-1901 and LR varieties, all the blanching methods led to a significant reduction in residual peroxidase activity, as well as affecting their color. The preservation of bioactive substances exhibited a microwave steam>hot water blanching trend. Blanching significantly increased the antioxidant activity of all the samples. Additionally, Fourier-transform infrared spectroscopy revealed that phytocompounds were retained to their maximum in microwave-blanched samples, especially at 300 W. The type of blanching method significantly affected the thermal properties of potatoes by disrupting the ordered structure of the matrix.

Discussion

Microwaves at 300 W can be used as a novel and suitable alternative technique for blanching potatoes, which successfully retained the original quality of it in comparison to steam and hot water blanching.

Evaluation of dry microwave and hot water blanching on physicochemical, textural, functional and organoleptic properties of Indian gooseberry (Phyllanthus emblica)

Indian gooseberry (Phyllanthus emblica) is a seasonal and highly nutritious fruit with shorter shelf-life and astringent taste limiting its utilization. The enzymatic browning and flavor loss are major concerns which makes pre-processing a crucial step for further processing. In this context, dry microwave blanching (MWB) was explored as an alternative to hot-water (HW) blanching to reduce its nutrition losses particularly ascorbic acid (AA) and makes it easier for removal of seed kernel. This study focused on the effect of MW power level (200–500 W) and blanching time (50–100 s) on AA content, color attributes (L*, a*, b*), and enzymatic inhibition in Indian gooseberry. The optimized MWB conditions were 294 W MW power with 70 s blanching time providing satisfactory enzymatic inhibition (75.47%), and retention of AA (417.70 mg/100 g pulp) and color attributes (L*: 58.42, a*: 4.57, b*: 26.23). As compared to HWB (80 °C, 5 min), MWB showed least AA degradation, higher total phenolic content and softening percent with less total color difference owing to its shorter processing time and dry blanching. Quantitative descriptive analysis (QDA) demonstrated that raw and MW blanched Indian gooseberries are the most accepted, followed by HW blanched samples. MWB showed better nutrient retention than HWB with easier seed removal showed the application of MW radiation for blanching of other fruits.

Effects of hot-air drying on the bioactive compounds, quality attributes, and drying and color change kinetics of coffee leaves

Drying is a key step that affects the chemical composition and quality of tea. In the present study, we reported the impacts of drying temperature and time on drying and color change kinetics, phytochemical composition, antioxidant activity, and surface microstructure of coffee leaves during hot-air drying. The results showed that drying temperature was positively (p < 0.05) correlated with the drying rate (DR), color index a* and total color change ΔE, and total soluble sugar (TSS), while negatively correlated with color indexes b* and L*, soluble protein content, and the DPPH scavenging capacity. Drying time has similar impacts on the color indexes and soluble protein as drying temperature. The content of total free amino acid and TSS increased by 62.5% and 47.4%, respectively, when coffee leaves were dried at 160°C for 24 min, under which the total phenolic content and DPPH and ABTS scavenging capacities reached the maximum of 108.04 mg GAE/g, 515.07 µmol Trolox/g, and 606.70 µmol Trolox/g, respectively. Drying significantly decreased the contents of chlorogenic acids and mangiferin and antioxidant activity, while high-temperature short-time drying helped retain phenolic compounds in coffee leaves. The DR fitted Page kinetic model. The color changes fitted the first-order kinetic models and the activation energies ranged from 16.00 to 31.06 kJ·mol^-1 . Prolonged drying time caused serious wrinkles on the surface of coffee leaves and the stomata closed. PRACTICAL APPLICATION: Drying decreased soluble protein while increasing free amino acid and soluble sugar. High-temperature short-time drying helps retain phenolics in the coffee leaves. The color change of coffee leaves during drying follows first-order kinetic. Prolonged drying time resulted in loosened texture of coffee leaves. Our study suggested that drying coffee leaves at 160°C for 24 min results in the coffee leaf tea being of better quality.

Chemical Evaluation of Liquidambar styraciflua L. Fruits Extracts and Their Potential as Anticancer Drugs

Liquidambar styraciflua L. is an aromatic species, popularly used in traditional Chinese medicine to treat diarrhea, dysentery, coughs, and skin sores. The present study was designed to investigate the chemical composition and biological potential of extracts obtained from the fruits of this plant. For the chemical evaluation, it was used mainly liquid and gas chromatography, plus NMR, and colorimetric methods. The aqueous extract (EA) originated two other fractions: an aqueous (P-EA) and an ethanolic (S-EA). The three extracts were composed of proteins, phenolic compounds, and carbohydrates in different proportions. The analyses showed that the polysaccharide extract (P-EA) contained pectic polysaccharides, such as acetylated and methyl esterified homogalacturonans together with arabinogalactan, while the fraction S-EA presented phenolic acids and terpenes such as gallic acid, protocathecuic acid, liquidambaric acid, combretastatin, and atractyloside A. EA, P-EA, and S-EA showed antioxidant activity, with IC50 values of 4.64 µg/mL, 16.45 µg/mL, and 3.67 µg/mL, respectively. The cytotoxicity followed the sequence S-EA > EA > P-EA, demonstrating that the toxic compounds were separated from the non-toxic ones by ethanol precipitation. While the fraction S-EA is very toxic to any cell line, the fraction P-EA is a promising candidate for studies against cancer due to its high toxicity to tumoral cells and low toxicity to normal cells.

Towards food circular economy: hydrothermal treatment of mixed vegetable and fruit wastes to obtain fermentable sugars and bioactive compounds

Due to processing activity, fruits and vegetables generate notable amounts of wastes at the processing, retail, and consumption level. Following the European goals for reducing food wastes and achieving a circular economy of resources, these biowastes should be valorized. In this work, hydrothermal hydrolysis at different conditions (temperatures, times, waste/water ratio, pH values) were tested to treat for first time; biowastes composed of mixed overripe fruits or vegetables to maximize the extraction of fermentable sugars that can be used as substrates in bioprocesses. Experimental data were fitted by a model based on irreversible first-order reactions, and kinetic constants were obtained. When hydrolysis of fruit wastes was carried out at 135 °C and pH 5 during 40 min, more than 40 g of reducing sugars per 100 g of waste (dry weight) could be obtained (represents an extraction of 97% of total carbohydrates). Concentrations of inhibitor compounds (HMF, furfural, acetic acid) in the hydrolysates were very low and, as example, a fermentation to obtain bioethanol was successfully carried out with an efficiency above 95%. Additionally, the production by hydrothermal treatment of bioactive compounds was investigated and the best results obtained were 92% DPPH inhibition and 12 mg GAE/g (dry weight) for antioxidant activity and phenolic compounds, respectively. These values are similar or even higher than those reported in literature using specific parts of fruits and vegetables.

Hot-Air Flow Rolling Dry-Blanching Pretreatment Improves the Drying Quality of Acanthopanax sessiliflorus by Increasing the Drying Rate and Inactivating Enzymes

The processing of Acanthopanax sessiliflorus has attracted interest due to its health benefits. In this work, an emerging blanching technology, called hot-air flow rolling dry-blanching (HMRDB), was employed to treat A. sessiliflorus before drying. The effects of varied blanching times (2–8 min) on enzyme inactivation, drying characteristics, bioactive compound retention, and microstructure were examined. The results demonstrated that blanching for 8 min rendered polyphenol oxidase and peroxidase nearly inactive. The blanching process reduced the drying time of samples by up to 57.89% compared to an unblanched sample. The Logarithmic model showed good fitting performance for the drying curves. The total phenolic and flavonoid content of the dried product increased as blanching time increased. The total anthocyanin content of the samples blanched for 6 min was 3.9 times higher than that of the unblanched samples, and 8 min of blanching produced the greatest DPPH• and ABTS• scavenging capabilities. The retention of active compounds in a dried product is a result of the inactivation of enzymes and a reduced drying period. Changes in the porous structure of the blanched samples would be responsible for the accelerated drying rate, according to microstructural analysis. These results indicate that HMRDB enhances the drying process and improves drying quality when applied to A. sessiliflorus before drying.

Microwaving released more polyphenols from black quinoa grains with hypoglycemic effects compared with traditional cooking methods

BACKGROUND

Polyphenols were reported to exhibit inhibitory effects on digestive enzymes to regulate carbohydrates and lipid digestion. However, different cooking methods might cause differences in the composition of polyphenols in cereal grains and thus further affect their activities.

RESULTS

The present study used boiling, roasting and microwaving to cook black quinoa and extracted polyphenols from them. Their total phenolic content (TPC) and total flavonoids content were determined, and phenolic composition was analyzed via high-performance liquid chromatography-mass spectrometry (HPLC-MS). Compared with other cooking methods, phenolic extract from microwaved black quinoa (PEM) showed the highest TPC value (about 2.64 mg GAE g^-1 ). Microwaving released more phenolic acids (ferulic acid and gallic acid) from black quinoa grains. PEM also exhibited the strongest antioxidant and α-glucosidase inhibitory activities. Lineweaver-Burk plots showed that PEM inhibited α-glucosidase in an uncompetitive mode, which was supported by circular dichroism analysis. PEM further reduced about 20.04% of digested starch in an in vitro digestion model and suppressed postprandial blood glucose increases (about 16.91% reduction) in vivo.

CONCLUSION

Collectively, our data suggested that microwaving could be an ideal method to cook quinoa in regards of its polyphenols in management of postprandial blood glucose. © 2022 Society of Chemical Industry.

Eugenol treatment delays the flesh browning of fresh-cut water chestnut (Eleocharis tuberosa) through regulating the metabolisms of phenolics and reactive oxygen species

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1.5 % EUG exhibited best inhibitory effect on browning in fresh-cut water chestnut.

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Phenylalanine ammonia-lyase of surface tissue was inhibited after eugenol treatment.

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Eugenol inhibited browning in fresh-cut water chestnut by regulating ROS metabolism.

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Eugenol enhanced ROS-scavenging enzymes and antioxidant capacity in surface tissue.

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Eugenol increased phenolic content and antioxidant capacity of inner tissue.

The potential mechanism behind the browning inhibition in fresh-cut water chestnuts (FWC) after eugenol (EUG) treatment was investigated by comparing the difference in browning behavior between surface and inner tissues. EUG treatment was found to inactivate browning-related enzymes and reduce phenolic contents in surface tissue. Molecular docking further confirmed the hydrophobic interactions and hydrogen bonding between EUG and phenylalanine ammonia-lyase (PAL). Moreover, EUG also enhanced reactive oxygen species (ROS)-scavenging enzyme activities, ultimately decreasing the O₂^- generation rates. Regarding inner tissue, EUG induced the accumulation of colorless phenolic compounds and increased the antioxidant capacity. In conclusion, 1.5 % EUG exhibited the best inhibitory effect on FWC browning, which partly attribute to the direct inhibitory effects on PAL activity. Furthermore, EUG could also enhance the enzymatic/non-enzymatic antioxidant capacity and alleviate the ROS damage to membranes, thereby, preventing the contact between oxidative enzymes and phenols and indirectly inhibiting the enzymatic browning in FWC.

Blanching Effect on the Quality and Shelf-Life Characteristics of Fresh Cowpea Grains [Vigna unguiculata (L.) Walp.]

The high perishability of fresh cowpeas impairs its commercialization. Thus, this study aims to determine the temperature-time binomial for blanching fresh cowpea [Vigna unguiculata (L.) Walp] by evaluating the effects of heat treatment and kinetic behavior on the peroxidase (POD) activity and on the physical characteristics (firmness, color, mass gain). A factorial design (3 × 6) with temperature (70, 80, and 90 °C) and time (1, 2, 4, 6, 8, and 10 min) was implemented. Physicochemical, microbiological, and enzymatic (POD) changes, in addition to photographic monitoring, were evaluated throughout the storage period (4.90 °C). With regard to the effects of the independent variables and the first-order kinetic model, it was determined that 70 °C for 4 min of blanching maintained and/or improved the physical characteristics of the raw material. The pH and the acidity of the blanched fresh cowpea changed little during the storage period; the microbiological load and POD activity reduced with blanching and remained stable until the eighth day of storage, and provided an increase of 5 days in shelf-life under refrigeration when compared to non-blanched. Blanching is shown as an alternative for improving fresh cowpeas, favoring an economic increase in production with guaranteed quality and safety attributes.

Experimental and computational study of fluidized-microwave drying process of shrinking parchment coffee and determination of quality attributes

This work presents the fluidized bed drying process combined with microwaves applied to Parchment coffee. In order to study different parameters that affect the quality of the grains, a mathematical model that describes energy and mass transfer during the drying process is presented and solved using Finite Elements Method (FEM) through COMSOL Multiphysics software. The model also considered the shrinkage of the grains due to water removal. Experiments were carried out in experimental prototype equipment obtaining the drying curves, which were utilized to validate the mathematical model. To study the impact of the operating conditions on the quality of the processed coffee, total polyphenolic content and antioxidant capacity were determined by Folin-Ciocalteau and free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods, respectively. Finally, nutritional parameters were related to operating conditions by the polynomial regression and desirability function methodology. Optimal operating conditions (1.4 m/s and 500 W) were found, which provides a product of excellent final quality.

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.

Impacts of novel blanching treatments combined with commercial drying methods on the physicochemical properties of Irish brown seaweed Alaria esculenta

Alaria esculenta is one of the most abundant edible brown seaweeds in Irelandandisconsidered an excellent source of nutrients, sought after by the food, nutraceutical and pharmaceutical industries. Seaweed is typically blanched and dried prior to consumption to enhance the end-product quality attributes and shelf life. Three blanching techniques were examined in this work; conventional hot water blanching, novel ultrasound blanching and microwave blanching. The L* and b*colour metrics were affected significantly (P < 0.01) by the processing methods. There were 76 volatile compounds detected in blanched and dehydrated Alaria esculenta. Freeze-dried samples after treatment with microwave alone (at 1000 W) and microwave (800 W) combined with ultrasound (at 50% amplitude) had the highest retention rate of volatile compounds (up to 98.61%). Regarding mineral content, drying methods significantly affected (P < 0.05) the content of Ca, Co, Cu and Fe, while blanching treatments significantly affected (P < 0.05) the content of Na, Cu, Fe and Mn.

Effects of short-wave ultraviolet light, ultrasonic and microwave treatments on banana puree during refrigerated storage

Enzymatic browning is a major problem in minimally processed banana puree; it reduces consumeŕs acceptability and affects nutritional quality. The objective of this work was to evaluate the effects ultrasound (40 kHz/10 min), microwave (800 W/ 25 s) and UV-C radiation (1.97 kJ/m²) applied to banana puree. Colour parameters (L*, a*, b*, chroma and hue), browning index (BI), polyphenol oxidase (PPO) and peroxidase (POD) activities, total phenolic compounds (TPC), antioxidant capacity (AOC) and microbiological counts were monitored throughout storage at 4°C. Ultrasound (US) and microwave (MW) treatments achieved a significant (p < 0.05) reduction in PPO activity and BI; moreover, ultrasound effectively retained phenolic compounds content (75% of initial value). The AOC was in coincidence with TPC values. POD activity was partially inhibited by UV-C while MW and US increase its activity. Although UV-C treatment was not effective to control browning development, it was effective to maintain microbiological stability after 20 days of storage (1.48 ± 0.01 log CFU/g). The evaluated treatments have the advantage of being less aggressive than conventional thermal treatments while maintaining fresh characteristics of the product.

Intensive pulsed light pretreatment combined with controlled temperature and humidity for convection drying to reduce browning and improve quality of dried shiitake mushrooms

BACKGROUND

The change of surface color caused by browning during the drying process of shiitake mushrooms seriously affects its market circulation. Intensive pulsed light (IPL) as a non-heat-treatment method can reduce enzyme activity by changing the enzyme structure. Therefore, in this study, the use of IPL pretreatment before drying was aimed to reduce the adverse reactions caused by the browning reaction during the drying processing of shiitake mushrooms.

RESULTS

Shiitake mushrooms pretreated with 25 pulses of IPL energy of 400 J reduced the initial polyphenol oxidase enzyme activity, the browning index, and browning degree values by 42.83%, 43.02%, and 47.54% respectively. The IPL pretreatment enhanced the polysaccharides and reducing sugars contents and it reduced 5-hydroxymethylfurfural generation in the dried shiitake mushrooms. The pretreatment also improved the surface color, the antioxidant activity, and retained the umami taste characteristics in the dried shiitake mushroom.

CONCLUSION

The IPL pretreatment combined with controlled temperature and humidity for convection drying could be a suitable method to improve the quality of dried shiitake mushrooms. Therefore, this study provides a new pretreatment method for materials that are prone to browning during drying. © 2021 Society of Chemical Industry.

Microwave technology: a novel approach to the transformation of natural metabolites

Microwave technology is used throughout the world to generate heat using energy from the microwave range of the electromagnetic spectrum. It is characterized by uniform energy transfer, low energy consumption, and rapid heating which preserves much of the nutritional value in food products. Microwave technology is widely used to process food such as drying, because food and medicinal plants are the same organisms. Microwave technology is also used to process and extract parts of plants for medicinal purposes; however, the special principle of microwave radiation provide energy to reaction for transforming chemical components, creating a variety of compounds through oxidation, hydrolysis, rearrangement, esterification, condensation and other reactions that transform original components into new ones. In this paper, the principles, influencing factors of microwave technology, and the transformation of natural metabolites using microwave technology are reviewed, with an aim to provide a theoretical basis for the further study of microwave technology in the processing of medicinal materials.

Impact of post harvest treatment on antioxidant activity and phenolic profile of Moringa oleifera lam leaves

Abstract

Moringa oleifera leaves are an important source of dietary phytochemicals, such as flavonoids with high antioxidant activity (AOA). These components are however influenced by the post-harvest treatments applied as well as the processing conditions. Hence, it is crucial to determine the most appropriate post-harvest treatment that preserves or enhances AOA. To this effect the influence of steam blanching, fermentation / oxidation, oven drying and roasting of fresh Moringa leaves on their AOA was investigated. Processing conditions of time and temperature for each treatment were optimised using response surface methodology. The effect of the different treatments at optimal conditions on phenolic profile and AOA were compared. Roasting achieved the most significant (p < 0.05) improvement in phenolics (43%) and AOA (22–31%), which was accompanied by the formation of 2 new compounds, quercetin-3-O-acetylglucoside and Quercetine-3-O-rhamnoside. Steam blanching had the most deleterious effect on phenolics (− 31%) and AOA. Post-harvest treatments qualitatively and quantitatively affect phytochemical profile of Moringa leaves.

Graphical abstract

Total Polyphenol and Flavonoid Content and Antioxidant Capacity of Some Varieties of Persea americana Peels Consumed in Cameroon

Fruit peels are increasingly being used as functional foods nowadays. Peelings of twelve varieties of Persea americana fruits consumed in Cameroon were investigated for their phenolic compounds (polyphenols and flavonoids) using three solvents systems, water, ethanol: water (50 : 50 v/v), and ethanol, and antioxidant activity using total antioxidant capacity (TAC), ferric reducing antioxidant power (FRAP), and 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging methods. Total polyphenol, flavonoids, and antioxidant potential of the peels significantly varied with P. americana variety and also with the extraction solvents in the order ethanol > ethanol: water > water. Total phenolic content varied from 2407 (Fuerte florid) to 673 (Semil) mg GAE/g DM, respectively, while flavonoids varied from 986 to 119 mg QE/g DM for Fuerte florid and Hickson varieties, respectively. TAC, respectively, varied between 132.87 and 126.85 mg AAE/g DM with Hass and Semil varieties, respectively. The highest DPPH scavenging capacity was recorded for the ethanolic extract with Lula (86.33%) and the least for the aqueous extract with the Semil (30.11%) variety. With FRAP, the highest capacity was obtained with hydroethanolic extract of Fuerte florid (0.43 mg AAE/g DM) and the least for aqueous extract with the Semil (0.269 mg AAE/g DM) variety. In conclusion, varieties of avocado peels are a good source of antioxidants. Solvent extraction significantly affected the concentration of bioactive compounds but not the potency of the antioxidants. A weakly positive correlation but not significant between the quantity of polyphenol, flavonoid, and antioxidant capacity of avocado peelings was obtained in this study.