Kinetics, biocompounds, antioxidant activity, and sensory attributes of quinces as affected by drying method

Quinces (Cydonia oblonga, Chaenomeles sp., and Pseudocydonia sinensis) as Medicinal Fruits of the Rosaceae Family: Current State of Knowledge on Properties and Use

In recent years, the evaluation of many plant-derived compounds as potential new drugs or functional foods has become an active research topic. The morphological characteristics of quinces of the genera Cydonia sp., Chaenomeles sp., and Pseuocydonia sp. are largely similar, which is why these fruits are often confused. Although they have been appreciated in Asia for centuries as a valuable component of local ethnomedicine, they are less known in Western countries, and scientific knowledge about their health benefits remains fragmentary. This literature review summarizes studies on the content of chemical compounds responsible for the health-promoting and functional properties of the quince fruit. It focuses on the content of carotenoids, vitamins, minerals, and carboxylic acids, although the main emphasis is on the content and diversity of bioactive polyphenols, which are extremely abundant in these fruits. The quince fruits are rich in antioxidants and compounds with proven anti-inflammatory, anticancer, antiallergic, and immunomodulatory effects. Their phytochemicals effectively regulate glycemia and improve the blood lipid profile, suggesting potential antidiabetic and cardioprotective benefits. Analysis of chemical characteristics showed that the Chaenomeles fruits. are underestimated as functional food ingredients. Studies on the molecular effects of their bioactive compounds and species-specific genomic analyses are sorely lacking in the scientific literature.

A Comparative Analysis of Thin-Layer Microwave and Microwave/Convective Dehydration of Chokeberry

Due to high water content, chokeberries (Aronia melanocarpa L.) are perishable. Therefore, energy-saving, combined drying technologies have been explored to improve the chokeberry drying. The combined microwave and the traditional convective drying method (MCD) have significantly enhanced the drying effectiveness, efficiency, and energy utilization rate and improved product quality. The MCD method, which implies the microwave power (MD) of 900 W for 9 s and the convective dehydration (CD) at 230 °C for 12 s, has the shortest dehydration time t (24 ± 2 min), has the maximum coefficient of diffusion (D_eff = 6.0768 × 10^-9 ± 5.9815 × 10^-11 m² s^-1), and represents the most energy effective for dehydration process (E_min = 0.382 ± 0.036 kWh). A higher water-holding capacity (WHC) characterized the chokeberries obtained by the MCD method compared to the regular microwave method (MD). The mildest MCD (15 s of MD on 900 W, 7 s of CD on 180 °C) could dehydrate chokeberries with the highest WHC (685.71 ± 40.86 g H₂O g^-1 d.m.) and the greatest evaluations for sensory attributes in terms of all properties. The results of this study provide the drying behavior of chokeberries that can help develop efficient drying methods and improve existing ones.

Infrared-assisted spouted bed drying of Chinese yam cubes: effect of constant and variable temperature drying processes on drying behavior, uniformity, and quality attributes

BACKGROUND

Infrared-assisted spouted bed drying (IRSBD) is an innovative hybrid drying technology based on infrared drying and spouted bed drying, which has the advantages of higher drying efficiency and better uniformity. Temperature is an important process parameter that affects drying characteristics and product quality. Considering the overall quality of the product, drying at a constant temperature may not be the best solution. However, there is a lack of research on dynamically varying drying schemes. In this study, the effects of constant and variable temperature drying processes on the drying characteristics, uniformity, energy consumption, and quality of Chinese yams were evaluated.

RESULTS

The shortest drying time and lowest energy consumption were obtained by IRSBD at 70 °C, followed by staged rising temperature drying (SRTD). However, SRTD achieved the best drying uniformity. The Peleg model could describe the dehydration kinetics of dried yams well (R²  > 0.99). A high drying temperature (70 °C) favored the preservation of bioactive compounds (polyphenols and flavonoids) and gave the best antioxidant activity and equilibrium rehydration ratio of dried yams but resulted in poor color. Samples dried with SRTD showed comparable good antioxidant activity and better color than those dried at 70 °C.

CONCLUSION

A reasonable variable temperature drying scheme using IRSBD is considered to be better when considering the drying performance and overall quality of the products. © 2022 Society of Chemical Industry.

Upcycling Quince Peel into Bioactive Ingredients and Fiber Concentrates through Multicomponent Extraction Processes

This study aimed to promote the total upcycling of quince (Cydonia oblonga Mill.) peel into bioactive extracts (BEs) and fiber concentrates (FCs). The multicomponent extraction processes were optimized using response surface methodology (RSM) coupled with a 20-run experimental design, where the effects of time (1-120 min), temperature (25-95 °C), and EtOH percentage (0-100%) were combined. In addition to the extraction yields, BEs were analyzed for phenolic compounds, organic acids, and other water-soluble constituents, while FCs were characterized for their color and dietary fiber content. Statistically valid theoretical models were obtained by fitting these dependent variables to a quadratic equation and used to predict optimal extraction conditions. Those obtained for phenolic compounds and malic acid were experimentally validated, yielding 9.3 mg/g and 7.6 g/100 g of these bioactive constituents, respectively, and about 51% (w/w) FC. These BEs showed in vitro antioxidant activity and antimicrobial effects against foodborne fungi and bacteria, standing out in some aspects in relation to synthetic food additives, mainly the malic acid-enriched BE. Overall, the developed extraction processes allowed valorizing of quince peel in FCs and BEs that could be used as natural fortifiers or preservatives in the formulation of foods, beverages and dietary supplements.

Valorization of quince peel into functional food ingredients: A path towards "zero waste" and sustainable food systems

Quince (Cydonia oblonga Mill.) is an astringent fruit widely processed into marmalade and other sweets through processes that discard the peel as a by-product. Therefore, this study was performed to characterize the quince peel composition in nutrients and phytochemicals and evaluate its in vitro biological activity, following a “zero waste” approach. The quince peel dry powder was particularly rich in fiber (20.2 g/100 g), fructose (34 g/100 g), malic acid (7.2 g/100 g), and potassium (692 mg/100 g). Extracts prepared by dynamic hydroethanolic maceration and hot water extraction yielded 4.70 and 4.27 mg/g of phenolic compounds, respectively, with a prevalence of flavan-3-ols. The hydroethanolic extract was the most effective in inhibiting lipid peroxidation and oxidative hemolysis, and also presented better antimicrobial effects against foodborne pathogens, which agreed with the highest flavan-3-ol contents. The extracts were better than control synthetic food additives against some tested fungal and bacterial strains. On the other hand, no ability to inhibit nitric oxide production or toxicity to the tumor and non-tumor cell lines was observed. Furthermore, the solid residues remaining after extraction contained 35–37 g/100 g of fiber. Overall, quince peel can be upcycled into fiber-rich and bioactive ingredients to endow the value chain with natural food fortifiers, preservatives, and health promoters.

Cider apple pomace as a source of nutrients: Evaluation of the polyphenolic profile, antioxidant and fiber properties after drying process at different temperatures

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Influence of cider apple pomace drying temperature was studied.

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Temperature affected drying kinetics and antioxidant and dietary fibre properties.

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Antioxidant properties were best preserved when drying in the range of 80–100 °C.

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The best properties of alcohol insoluble residue were found when drying at 40–60 °C.

Apple pomace, the by-product of the cider industry, contains a high content of antioxidant compounds and dietary fiber. Drying would allow its preservation for a later use. The aim of this study was to evaluate the effect of the drying temperature on the drying kinetics, antioxidant properties and the fiber characteristics. For this, drying experiments were performed at different temperatures (40–120 °C). The increase in temperature enhanced the drying rate, as was shown by the effective diffusivity and mass transfer coefficient identified by modelling. The influence of temperature was quantified through the activation energy (38.21 kJ/mol). Regarding the retention of antioxidant properties, the best results were found at 80–100 °C while 40–60 °C was the best temperature range for the fiber characteristics. Therefore, 80 °C could be an adequate temperature for drying of cider apple pomace, as it represents a good balance between kinetics, and antioxidant and fiber properties.

Interaction of Different Drying Methods and Storage on Appearance, Surface Structure, Energy, and Quality of Berberis vulgaris var. asperma

Seedless barberry fruit is native small fruit in Iran. To examine the impact of various drying methods and storage on the biochemical attributes (Vitamin C, Anthocyanin, Phenol, pH, TA), color index (a*, b*, L*, ab, and Chroma), drying time, and fruit microstructure (by SEM) of seedless barberry (Berberis vulgaris var. asperma), and effective moisture diffusivity coefficient (D_eff), specific energy consumption (SEC), energy efficiency (EE) of the dryers, this experiment was performed. Drying treatments include microwave (100, 170, and 270 W), oven (60 and 70 °C), cabinet (50 and 70 °C), shade, sun, and fresh samples (control) and storage 6 months after drying (in polyethylene packaging and at a temperature of 5–10 °C). Results showed minimum and maximum drying times (50 min and 696 h), were related to microwave (270 W) and shade methods, respectively. The highest color values were observed in fruits treated with control, shade and sun treatments and the lowest values were observed in cabinet (70 °C) methods. According to the SEM results, microwave significantly affected surface structure of the dried sample compared to others. The findings indicated that the use of artificial drying methods than natural methods (sun and shade) cause a more significant reduction in color indexes, while vitamin C, soluble solids, and anthocyanin were significantly maintained at a high level. Storage reduced anthocyanin content of fruits almost 12%. Moreover, it was discovered EE and SEC values varied in the range of 1.16–25.26% and 12.20–1182 MJ/kg, respectively. D_eff values were higher in microwave 270 W.

Quince fruit Cydonia oblonga Mill nutritional composition, antioxidative properties, health benefits and consumers preferences towards some industrial quince products: A review

Quince fruit (Cydonia oblonga) that belongs to the Rosaceae family and native to the Mediterranean region has been studied for decades for its unique importance in food and medicine. This fruit is packed with vitamins, minerals as well as fibers, pectin and tannins. Quince is known by its many therapeutic effects that include antioxidant, anti-inflammatory, antimicrobial, anti-ulcerative, and anticancer actions. However, this fruit is underutilized at the level of food processing due to its sensory attributes and the limited appreciation of its benefits by both farmers and consumers. Other than jellies and jams, quince could be processed into various healthy sub-products. The aims of the current review are to present botanical and nutritive value of this fruit, review the available literature on its therapeutic effects in order to increase farmers and consumers awareness about the importance of quince fruit and showing the different ways of utilizing it.

Comparison of Different Drying Methods for Asparagus [Asparagus cochinchinensis (Lour.) Merr.] Root Volatile Compounds as Revealed Using Gas Chromatography Ion Mobility Spectrometry

Asparagus [Asparagus cochinchinensis (Lour.) Merr.] is a traditional herbal medicine plant commonly used to nourish yin, moisten dryness, and clear fire cough symptoms. Drying is an excellent option to conserve food materials, i.e., grains, fruits, vegetables, and herbs, reducing the raw materials volume and weight. This study aims to evaluate different drying approaches that could increase the value of asparagus, particularly as an ingredient in fast foods or as nutraceutical byproducts. The volatile components of asparagus roots were analyzed by using headspace-gas chromatography-ion mobility spectroscopy under different drying conditions, i.e., natural drying (ND) at ambient air temperature in the dark, well-ventilated room, temperature range 28-32°C, blast or oven drying at 50°C, heat pump or hot-air drying at temperature 50°C and air velocity at 1.5 ms-1 and vacuum freeze-drying at the temperature of -45°C and vacuum pressure of 10-30 Pa for 24 h. The findings revealed that the various drying processes had multiple effects on the color, odor index, and volatile compounds of the asparagus roots. As a result of the investigations, multiple characteristics of components, therefore, exploitation and comparison of various flavors; a total of 22 compounds were identified, such as alcohols, ketones, aldehydes, acids, esters, heterocyclic, and terpene. The present findings may help understand the flavor of the processed asparagus roots and find a better option for drying and processing.

Reactivity of flavanols: Their fate in physical food processing and recent advances in their analysis by depolymerization

Flavanols, a subgroup of polyphenols, are secondary metabolites with antioxidant properties naturally produced in various plants (e.g., green tea, cocoa, grapes, and apples); they are a major polyphenol class in human foods and beverages, and have recognized effect on maintaining human health. Therefore, it is necessary to evaluate their changes (i.e., oxidation, polymerization, degradation, and epimerization) during various physical processing (i.e., heating, drying, mechanical shearing, high-pressure, ultrasound, and radiation) to improve the nutritional value of food products. However, the roles of flavanols, in particular for their polymerized forms, are often underestimated, for a large part because of analytical challenges: they are difficult to extract quantitatively, and their quantification demands chemical reactions. This review examines the existing data on the effects of different physical processing techniques on the content of flavanols and highlights the changes in epimerization and degree of polymerization, as well as some of the latest acidolysis methods for proanthocyanidin characterization and quantification. More and more evidence show that physical processing can affect content but also modify the structure of flavanols by promoting a series of internal reactions. The most important reactivity of flavanols in processing includes oxidative coupling and rearrangements, chain cleavage, structural rearrangements (e.g., polymerization, degradation, and epimerization), and addition to other macromolecules, that is, proteins and polysaccharides. Some acidolysis methods for the analysis of polymeric proanthocyanidins have been updated, which has contributed to complete analysis of proanthocyanidin structures in particular regarding their proportion of A-type proanthocyanidins and their degree of polymerization in various plants. However, future research is also needed to better extract and characterize high-polymer proanthocyanidins, whether in their native or modified forms.

Physico-chemical aspects of Thai fermented fish viscera, Tai-Pla, curry powder processed by hot air drying and hybrid microwave-infrared drying

The objective of this research was to comparatively investigate the effect of hot air drying (HA) and hybrid microwave-infrared drying (MI) on physico-chemical characteristics of Thai fermented fish viscera, Tai-Pla, curry powder (TCP). HA was carried out at 60°C, 70°C, and 80°C and MI was carried out at a microwave power of 740, 780, and 810 W with a constant infrared heating power (500 W) for different drying times to obtain the final moisture content ≤ 12.0% and the water activity (aw) ≤ 0.6. The quality characteristics of TCP were governed by HA temperature and MI output power. TCP dried using HA and MI at all conditions had similar contents of protein, lipid, ash, fiber, and carbohydrate (p>0.05). The fastest drying rate was detected when MI at 810 W for 40 min was applied (p<0.05). In this condition, TCP had the lowest browning index (A294 and A420) and the highest lightness (L* value) (p<0.05). TCP dried with MI at all powers had higher phenolic content and lower TBARS compared to HA (p<0.05). However, no significant differences in DPPH• scavenging activity were observed among TPC made by HA and MI (p>0.05). Similar Fourier transform infrared (FTIR) spectra with different peak intensities were observed in all samples, indicating the same functional groups with different contents were found. The bulk density of all TCP ranged from 0.51 g/mL to 0.61 g/mL and the wettability ranged from 24.02% to 26.70%. MI at 810 W for 40 min effectively reduced the drying time (5-fold faster) and lowered the specific energy consumption (18-fold lower) compared to the HA at 60°C for 210 min. Therefore, MI is a promising drying technique to reduce the drying time and improve the overall quality of TCP.

Combined Hot Air, Microwave, and Infrared Drying of Hawthorn Fruit: Effects of Ultrasonic Pretreatment on Drying Time, Energy, Qualitative, and Bioactive Compounds' Properties

The present study aimed to examine the effect of ultrasonic pretreatment and hot air, microwave–hot-air, infrared–hot air, and freeze-drying on the drying time, specific energy (SE), qualitative properties (i.e., color, shrinkage, and rehydration ratio), and bioactive compounds’ properties (i.e., antioxidant activity, phenolic, and flavonoid contents) of hawthorn fruit. Drying of hawthorn was conducted from 45 min for the ultrasonic + microwave–hot-air drying to 1280 min for the freeze-drying method. The lowest amount of SE was obtained using the ultrasonic-microwave–hot-air drying method, which was 47.57 MJ/kg. The lowest values in color changes (12.25) and shrinkage (17.21%) were recorded for the freeze-drying method, while the highest amounts for these traits were 45.57% and 66.75% in the HA drying, respectively. In general, the use of different drying methods reduces the antioxidant capacity (AC), total phenolic content (TPC), and total flavonoid content (TFC) during processing compared to fresh samples. The highest values for AC, TPC, TFC, and the rehydration ratio were 30.69%, 73.07 mg-GAE/gdw, 65.93 mg-QE/gdw, and 2.02 for the freeze-drying method, respectively.

Drying methods and structure-activity relationships of hydroxycinnamic acid derivatives in Idesia polycarpa Maxim. Leaves

Idesia polycarpa Maxim. leaves are an excellent source of hydroxycinnamic acid derivatives and have drawn special attention due to their various biological activities. However, the effects of post-harvest treatment on the structure-activity relationships of hydroxycinnamic acid derivatives in leaves of I. polycarpa are still unknown. In the current study, we compared the contents of unstable compounds in leaves with four drying methods, namely sun-drying, freeze-drying, shade-drying, and oven-drying. We found that the four hydroxycinnamic acid derivative isomers of leaves were significantly affected after drying processing with four different drying methods. Consequently, the underlying mechanisms responsible for the variation of these compounds during the drying processes have been well elucidated: UV lighting induced the isomerization of 1-[(6'-O-(E)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (1) and 1-[(4'-O-(E)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (3) into 1-[(6'-O-(Z)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (2) and 1-[(4'-O-(Z)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (4). Also, heat (exceeding 20 °C) led to the rearrangement of the (E/Z)-p-coumaric acid moiety of compounds 3 and 4, of which the 4-O-acylglucoses changed into the 6-O-acylglucoses to generate compounds 1 and 2, respectively. Interestingly, the hepatocyte-free fatty acid accumulation in OA-induced steatosis-conditioned HepG2 cells decreased by 65.00%, 10.69%, and 47.00%, respectively, following treatment with compounds 2, 3 and 4, and compound 1 presented no lipid-lowering activity. In addition, the bioactivities of compounds 2 and 4 were substantially enhanced by 58.42% and 25.33% with the sun-drying method compared to the freeze-dying methods. Our study suggests that sun-drying processing is the best method among the four drying processing methods of I. polycarpa Maxim. leaves.

Effect of Selected Drying Methods and Emerging Drying Intensification Technologies on the Quality of Dried Fruit: A Review

Drying is one of the oldest methods for food preservation that removes the water from fruit and makes it available for consumption throughout the year. Dried fruits can be produced by small- and large-scale processors, which makes them a very popular food among consumers and food manufacturers. The most frequent uses of drying technology include osmotic dehydration, vacuum drying, freeze-drying and different combinations of other drying technologies. However, drying may provoke undesirable changes with respect to physiochemical, sensory, nutritional and microbiological quality. Drying process energy efficiency and the quality of dried fruits are crucial factors in fruit drying. Recently, innovative technologies such as ultrasound, pulsed electric field and high pressure may be used as a pretreatment or in combination with traditional drying technologies for process intensification. This could result in quality improvements of dried fruits and enhanced efficiency and capacity of the production process, with a positive impact on environmental and economic benefits.

Effects of Different Drying Methods on the Retention of Bioactive Compounds, On-Line Antioxidant Capacity and Color of the Novel Snack from Red-Fleshed Apples

The aim of this study was to determine the effect of different drying methods: convective (at 50, 60, 70 °C), vacuum-microwave (at 120, 240, 360, 480 W and 360 W with reduction to 120 W) and hybrid (convective pre-drying at 50, 60, 70 °C followed by vacuum-microwave drying at 120 W) on the quality parameters of novel red-fleshed apple fruit snacks (RFAs), such as phenolics, on-line antioxidant capacity, water activity and color. Drying kinetics, including a temperature profile of dried material, and modified Page model were determined. Freeze-drying was used as a control method. The highest content of bioactive compounds in the samples was retained following freeze-drying, then hybrid, vacuum-microwave and finally convection drying. The antioxidant capacity measured by on-line 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), identified anthocyanins, flavan-3-ols and phenolic acid as the main compounds responsible for this activity. Unfavorable changes in color, formation of hydroxymethylfurfural (HMF) and degradation of polyphenolics were noted along with increasing drying temperature and magnetron power. The red-fleshed apple snacks are a promising high-quality dehydrated food product belonging to functional foods category.

Comparison of Traditional and Novel Drying Techniques and Its Effect on Quality of Fruits, Vegetables and Aromatic Herbs

Drying is known as the best method to preserve fruits, vegetables, and herbs, decreasing not only the raw material volume but also its weight. This results in cheaper transportation and increments the product shelf life, limiting the food waste. Drying involves the application of energy in order to vaporize and mobilize the moisture content within the porous products. During this process, the heat and mass transfer occurs simultaneously. The quality of dehydrated fruits, vegetables, and aromatic herbs is a key problem closely related to the development and optimization of novel drying techniques. This review reports the weaknesses of common drying methods applied for fruits, vegetables, and aromatic herbs and the possible options to improve the quality of dried products using different drying techniques or their combination. The quality parameters under study include color, bulk density, porosity, shrinkage, phytochemicals, antioxidant capacity, sugars, proteins, volatile compounds, and sensory attributes. In general, drying leads to reduction in all studied parameters. However, the behavior of each plant material is different. On the whole, the optimal drying technique is different for each of the materials studied and specific conditions must be recommended after a proper evaluation of the drying protocols. However, a novel or combined technique must assure a high quality of dried products. Furthermore, the term quality must englobe the energy efficiency and the environmental impact leading to production of sustainable dried products.

Volatile Composition and Sensory Properties as Quality Attributes of Fresh and Dried Hemp Flowers (Cannabis sativa L.)

Flowers of hemp (Cannabis sativa L.) are widely used in cosmetics, food, and in the pharmaceutical industry. The drying process plays a key role in retention of aroma and also in the quality of products. Seven variants of hemp flower drying, including convection drying (CD), vacuum–microwave drying (VMD), and combined drying consisting of convective pre-drying followed by vacuum–microwave finishing drying (CPD-VMFD) were checked in this study. For each process, we applied the two-term model. Dried material was submitted to color and chromatographical assessments. Analyses of obtained essential oil showed the presence of 93 volatile compounds, predominantly β-myrcene, limonene, and β-(E)-caryophyllene, as well as α-humulene. Application of 240 W during VMD and 50 °C during CD gave the highest retention of aroma compounds, amounting to 85 and 76%, respectively, but with huge color changes. Additionally, sensory analysis proved that drying with a microwave power of 240 W provides a product most similar to fresh material.

Hydroxycinnamic Acids and Carotenoids of Dried Loquat Fruit cv. 'Algar' Affected by Freeze-, Convective-, Vacuum-Microwave- and Combined-Drying Methods

The effect of different drying techniques (freeze, convective, vacuum-microwave and combined drying) on the drying kinetics, the phytochemical compounds and sensory characteristics in loquat cultivar 'Algar' was studied. The convective drying resulted in the highest amount of total hydroxycinnamic acids (5077 mg/kg wet weight (ww)), with 3-caffeoyl quinic acid and 5-caffeoyl quinic acid being the greatest carotenoids. The highest values of total carotenoids were obtained by the freeze-drying technique (2601 mg/kg ww), followed by all convective treatments and vacuum-microwave at 360 W. The highest carotenoid was β-carotene. The ABTS+• (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and FRAP (Ferric Ion Reducing Antioxidant Power) values ranged from 2.04 up to 3.27 mmol Trolox/100 g ww, and from 1.89 up to 2.29 mmol Trolox/100 g ww, respectively. As expected, the color difference of freeze-dried samples was the lowest (7.06), similar to combined drying conditions (9.63), whilst the highest value was found after convective drying (37.0). All treatments were sensory acceptable (no off-flavors). However, still, further research is needed to fully optimize these studied drying treatments because the freeze-dried sample still had higher carotenoid content and better instrumental color parameters. Although recently the impact of microwave drying has been studied, this is the first work comparing phytochemical composition of loquat fruit under the different drying methods mentioned above.

Characterization of dried horseradish leaves pomace: phenolic compounds profile and antioxidant capacity, content of organic acids, pigments and volatile compounds

Horseradish (Armoracia rusticana) leaves pomace, which contains high-value bioactive compounds, is the product resulting from pressing horseradish leaves for juice production. The aim of the current research was to investigate the effect of convective, microwave-vacuum and freeze-drying on the content of bioactive compounds in horseradish leaves pomace. Convective hot air-drying was performed at 40, 60 and 80 °C. The total phenolic content (TPC), total flavonoid content (TFC), total flavan-3-ol content, total phenolic acid content, total flavonol content, chlorophylls and total carotenoids, and antioxidant activity were determined by spectrophotometric methods. Individual profiles of phenols and organic acids are estimated by high-performance liquid chromatography (HPLC), but volatile compounds are estimated by gas chromatography (GC). Totally, 14 individual phenolic compounds, 8 organic acids, and 49 volatile compounds were analysed in the studied samples. The main phenolic compound identified in horseradish leaves pomace was rutin (3231 mg/100 g DW), among organic acids—quinic and malic acids, and volatile compounds—allyl isothiocyanate, 3-butenenitrile and benzyl alcohol. In the drying process, the content of some (total flavan-3-ols, total carotenoids content) compounds increased, but others (TPC, total organic acids content) decreased, and it was drying method-dependent. Freeze-drying caused the reduction of TPC by 29%, whereas convective drying by 53–59%. Fresh pomace contains such isothiocyanates as allyl isothiocyanate and butyl isothiocyanate, which were completely lost in the drying process. Freeze-drying allowed the best retention of various phenolic and volatile compounds in horseradish leaves pomace.

The influence of different carrier agents and drying techniques on physical and chemical characterization of Japanese quince (Chaenomeles japonica) microencapsulation powder

Fruit powders can become a new and innovative direction of using the potential of Japanese quince (JQ) fruit in an affordable form. Therefore, physical (dry matter, true and bulk density, porosity and color) and chemical parameters of JQ juice powders obtained by using different carrier agents and drying techniques were evaluated. The juice was mixed with maltodextrin, inulin and a mixture of both in different proportions and dried using freeze, spray, and vacuum (50, 70, and 90 °C) drying techniques. The identification and quantification of phenolic compounds in JQ juice powders were performed by LC-PDA-QTOF-MS and UPLC-PDA, respectively, while antioxidant capacity was measured using ABTS, FRAP and ORAC assays. In addition, enzymatic in vitro inhibition tests of α-glucosidase, pancreatic lipase, acetylcholinesterase and 15-lipoxygenase were performed. Among the drying techniques applied, freeze-drying resulted in the highest retention of polyphenols, while among the carrier agents maltodextrin was found to be the best biopolymer for obtaining high-quality fruit powder and also ensured powders with the lowest content of undesirable hydroxymethylfurfural.

Comprehensive evaluation of physicochemical properties and antioxidant activity of B. subtilis-fermented polished adlay subjected to different drying methods

The physicochemical properties and antioxidant activity of B. subtilis-fermented polished adlay (BPA) subjected to different drying methods (hot-air drying, HAD; infrared-radiation drying, IRD; vacuum drying, VD; microwave-vacuum drying, MVD; and freeze-vacuum drying, FVD) were evaluated in this study. Results showed FVD was ideal for maintaining the natural appearance and higher contents of proximate compositions, free fatty acids, tetramethylpyrazine (6.91 mg/g DW), coixol (0.62 mg/g DW), coixenolide (4.21% DW), coixan (35.10% DW), and triterpenoids (17.41 mg/g DW). The higher contents of total phenolics and flavonoids, stronger antioxidant activity, and higher color differences were observed in HAD and IRD samples. MVD displayed the shorter drying time, higher γ-aminobutyric acid content, and higher retention ratios of tetramethylpyrazine (75.54%), coixol (87.10%), coixenolide (98.57%), and coixan (99.11%). Pearson's correlation coefficient exhibited that the positive correlation between the contents of phenolics and flavonoids and the antioxidant activities of all dried BPA samples was observed (R 2 > 0.881, p < .05). Principal component analysis showed that the top three categories of comprehensive quality were FVD-, MVD-, and VD-treated BPA samples. In conclusion, MVD should be a potential preservation method to obtain high-quality dried BPA for short drying time and high comprehensive quality.

Effect of microwave and oven drying processes on antioxidant activity, total phenol and phenolic compounds of kiwi and pepino fruits

Kiwi and pepino fruits are most valuable fruits as they contains substantial amounts of nutrients and bioactive compounds. These fruits exhibited several health potentials such as antioxidant, antiinflammatory, antiobesity, antihyperlipidemia, and anticancer properties. However, studies on the effect of microwave and conventional drying methods on the antioxidant activity and bioactive compounds of kiwi and pepino fruits are limited. Therefore, this study was conducted to assess the effect of microwave and oven drying methods on antioxidant activity, total phenolic, and phenolic compounds of kiwi and pepino fruits. Drying of the fruit samples was carried out using conventional (70 °C for 20 h) and microwave (720 W for 3 min) ovens. 1,1-diphenyl-2-picrylhydrazyl scavenging and colorimetric Folin-Ciocalteu assays were used to assess the antioxidant activity and total phenolic contents, respectively, of fresh and dried fruits. Both drying methods significantly (p < 0.05) decreased the moisture contents of both fruits compared to untreated controls. Concomitantly, drying methods also enhanced (p < 0.05) antioxidant activity and total phenolic content of both fruits with the highest improvement being observed for microwave-dried fruits compared to untreated controls. In addition, a significant increase was observed in catechin and 1,2-dihydroxybenzene content of kiwi and pepino after drying process. However, microwave drying method reduced the amount of 3,4-dihydroxybenzoic acid in kiwi (ranging from 34.120 to 9.350 mg/100 g) and pepino (varied from 33.414 to 15.445 mg/100 g). Generally, the highest antioxidant activity and phenolic contents were reported in microwave oven dried samples, followed by samples dried in oven and fresh fruits. The results revealed that microwave drying could be more useful in fruit drying than conventional drying. In addition, dried kiwi and pepino fruits contains substantial quantities of phenolic compounds with high antioxidant activity compared to fresh fruits, and thus they are considered as healthy food.

The effect of pre-treatment methods on the quality of dehydrated candied Japanese quince fruits during storage

Candied quince is one of the most popular processing products of Japanese quince (Chaenomeles japonica) in Latvia. During the storage of dehydrated fruit, the colour turns darker, thus negatively influence the overall quality and consumers' acceptability of the product. The aim of the present study was to evaluate the effectiveness of different anti-browning agents in combination with fruit blanching and soaking as a type of pre-treatment to preserve the colour of candied quince during 8-months storage. The fruit were harvested at various maturity stage (i.e. unripe, semi ripe and ripe) with the following pre-treatment using three anti-browning agents (l-cysteine, NATRApHASE^®ABAF and Natureseal^® AS1). Hunter L (whiteness/darkness), a (redness/greenness) and b (yellowness/blueness) values were used to measure change in colour. These values were also used for calculation of the total colour change (ΔE*). Considering blanching and soaking as a type of treatment. Best results were obtained with blanching treatment. L* values decreased significantly after dehydration, showing that the samples became darker, during the further 8-months storage, L* values increased, positively influencing the colour of the tested fruit. The data obtained using the Analytic Hierarchy Process Analysis revealed that 0.3% l-cysteine was the best for effective prevention of colour change during long-term storage among the tested agents.