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This study examined the effects of vacuum, ethanol pretreatment, and infrared-hot air drying methods on the characteristics and quality of scallion slices. The pretreatment of scallion includes four conditions: 1) Control: soaking in distilled water under normal pressure, 2) Ethanol: soaking in 75% ethanol under normal pressure, 3) Water + VC: soaking in distilled water under a vacuum of 0.6 bar, 4) Ethanol + VC: soaking in 75% ethanol under a vacuum of 0.6 bar. The pretreatment times were 5, 10, 20 and 30 min. The drying process was done in an infrared hot air drying oven at 60 °C. The ethanol pretreated samples exhibited better rehydration, odor, vitamin C retention, bactericidal effect and significantly reduced drying time. Water + VC samples showed better scallion morphology and color. Ethanol + VC samples showed the combined advantages of ethanol and Water + VC pretreatments. Therefore, Ethanol + VC pretreatment can significantly improve the drying rate and quality of scallion.

Fresh apricots pre-treated by pulsed electric fields at different intensities [LPEF, 0.65 kV/cm, 100 Hz, 20 µs and total treatment time 30 s; HPEF1, 1.25 kV/cm, 100 Hz, 20 µs and total treatment time 30 s; HPEF2, 1.25 kV/cm, 100 Hz, 20 µs and total treatment time 60 s], along with controls [non-treated, non-treated and sulphite treated, and heat pre-treatment at 80 °C, for 10 min (HC)] and soaked in 0.2% sodium sulphite solution for 1 h and then were subject to hot air drying. The changes in drying rate, polyphenol oxidase, peroxidase, and β-carotene contents as well as antioxidant activity and colour in pre-treatment and hot air-dried apricot samples were investigated. PEF and heat treatments increased the drying rate of apricots. PEF treatments had no effect on the PPO activity and decreased the POD activity (p

The present study aimed to investigate the effect of hot air drying (HD), microwave rolling-bed drying (MRD), hot air microwave rolling-bed drying (HMRD), pulse-spouted microwave vacuum drying (PSMVD) and freeze-drying (FD) on the drying characteristics, quality properties and microstructure of edamame. Six models were fitted the drying curves, and quality attributes were analyzed. Results indicated that Page model was the most suited model for edamame drying. Compared with HD, MRD and HMRD improved the quality of edamame and decreased the drying time by 45.59% and 36.03% respectively. The FD and PSMVD possessed higher rehydration ability, nutrient retention and antioxidant capacity compared with other methods. Moreover, PSMVD products showed a crunchy texture, the less color change and the shortest drying time (70 min). Microscopy images demonstrated a distinct porous structure in PSMVD, which facilitated the moisture transfer. Overall, PSMVD is a promising dehydration method for obtaining high value-added edamame products.

Various drying techniques play an important role in foodstuff preservation. However, the role of different drying techniques on garlic quality is limited. The purpose of this study was to investigate the effect of vacuum freeze-drying (VFD), hot air drying (HAD), infrared hot air drying (IRHAD), relative humidity drying (RHD) and pulsed vacuum drying (PVD) on the physical, rehydration, flavor, bioactive compounds and antioxidant characteristics of garlic slices. Results showed that garlic slices treated with VFD had an attractive color, low shrinkage, low hardness, and the lowest rehydration capacity. The volume shrinkage ratio, thermal stability and storage stability of garlic slices after HAD were the highest. Different dried garlic samples had different specific flavor fingerprints. IRHAD and RHD dried samples showed the highest rehydration capacity, content of bioactive compounds and antioxidant activity. The findings could provide a scientific basis to help in future large-scale production of good quality dried garlic products.

In order to evaluate the effects of drying methods on the drying characteristics, quality (color, volatile oil (VO) content, shikimic acid (SA) content, trans-anethole content in the star anise volatile oil (TA-O)) and flavor components of star anise (Illicium verum Hook.f.), we tested five different methods (hot air drying (HAD), heat pump drying (HPD), far infrared radiation drying (FIRD), microwave drying (MD), and sun drying (SD)) with or without blanching to dry fresh star anise. Results showed MD had a shorter drying time than others, as well as the highest SA content (125.56 mg/g d.b.). HPD sample exhibited higher VO content (12.27% d.b.) and TA-O (113.30 mg/g d.b.) than those dried with other methods. HPD can improved the dominant flavor compounds of star anise, including trans-anethole (4165.46 mg/100 g d.b.), estragole (176.50 mg/100 g d.b.), linalool (280.69 mg/100 g d.b.), and (+)-limonene (471.18 mg/100 g d.b.). Samples treated with HPD-B had the highest comprehensive score (4.59) in the flavor principal component analysis. Therefore, HPD was more suitable for star anise drying as it maintaining quality. The better quality (higher flavor quality and better appearance) was found in HPD-B.

Thinned peach is abundant in polyphenols, and has been shown to exhibit various bioactivities. In this study, we evaluated the underlying immunomodulatory activity of polyphenol extracts of thinned peach (PETP) via the NF-κB and Nrf2 signaling pathways in RAW264.7 macrophages. The results demonstrated that the PETP efficiently activated the nuclear translocation of NF-κB and Nrf2, as well as downstream cytokines (IL-1β, IL-6, TNF-α and IFN-γ), SOD activity and ROS levels in RAW264.7 cells. Specifically, the PETP of natural drying and hot air drying exhibited less efficacy than that of freeze drying in NF-κB pathway. Interestingly, the PETP of hot air drying at 50 °C was more effective than freeze-dried PETP in activating Nrf2 nuclear translocation. Additionally, 50 µg/mL PETP enhanced immune responses, whereas 800 µg/mL PETP inhibited inflammatory development in macrophages. These findings indicated that different PETP affected the immunomodulation effects differently, which associated with the drying methods and incubation concentrations.

The purpose of this research was to study the effect of hot air drying, microwave vacuum drying and freeze drying combined with explosion puffing drying (HDEPD, MDEPD and FDEPD) on physicochemical properties, antioxidant activities and flavor characteristics of apples. The results showed that MDEPD and FDEPD products had better color and textural properties, exhibited a homogeneous porous structure. MDEPD and FDEPD better preserved scavenging abilities of DPPH, hydroxyl radical and FRAP, retained values of TFC and TPC. Aroma characteristics and taste properties of apples obviously changed with different drying methods, and drying qualities of products could be classified in terms of volatile compounds and taste profiles. Two principal components were able to describe 90.12% and 69.43% of the total volatile compound variance and total taste profile variance, respectively. Three main clusters of dried apples were identified, MDEPD and FDEPD can be used to enhance drying qualities of apple products.

This research explored the application of combined radio frequency and hot air drying (RF-HAD) technology on corn seeds. Drying characteristics and seed vigor were investigated at different RF electrode gaps (140, 150 and 160 mm). To better demonstrate the feasibility of applying RF-HAD on corn seeds, tempering-intermittent hot air drying (HAD) was studied as a comparison. Reduced electrode gap corresponding to elevated average heating rate and power efficiency resulted in decreased seeds vigor and specific energy consumption. The assistance of RF significantly increased the drying rate of corn seeds and reduced drying duration by up to 70% compared with HAD. A higher dehydrogenase activity (DHA) but a lower germination percentage (GP) was observed in RF-HAD samples as compared with HAD ones. Corn seeds were promoted to be dormant by RF-HAD according to dormancy-breaking results and isobaric tags for relative and absolute quantification (iTRAQ) analysis.

Relationship among pH, generation of free amino acids (FAAs), and Maillard browning was investigated in Japanese common squid during air drying at 40 °C to prevent its discoloration. In the surface color measurement, increase in the b* value which is an indicator for Maillard browning of the dried squid was mitigated at pH 4.0-6.0 and accelerated at pH 7.5-9.0. Adjusting the pH to 5.5 effectively suppressed increasing of the b* value (p 0.05). Arginine (Arg) generation involved in the Maillard reaction, was inhibited in the dried squid at pH 5.5 (p 0.05). Maillard reactivities between ribose and amino acids were lower at pH 4.0 than at pH 5.5 (p 0.05). These results indicate that browning of the dried squid is significantly suppressed at pH 5.5. Moreover, suppression of Arg generation is more effective than weakening of Maillard reactivity between ribose and Arg, in mitigating Maillard browning of the dried squid at an acidic pH.

Bananas (cv. Musa nana and Musa cavendishii) fresh and dried by hot air at 50 and 70 C and lyophilisation were analysed for phenolic contents and antioxidant activity. All samples were subject to six extractions (three with methanol followed by three with acetone/water solution). The experimental data served to train a neural network adequate to describe the experimental observations for both output variables studied: total phenols and antioxidant activity. The results show that both bananas are similar and air drying decreased total phenols and antioxidant activity for both temperatures, whereas lyophilisation decreased the phenolic content in a lesser extent. Neural network experiments showed that antioxidant activity and phenolic compounds can be pre- dicted accurately from the input variables: banana variety, dryness state and type and order of extract. Drying state and extract order were found to have larger impact in the values of antioxidant activity and phenolic compounds.

The aim of this research was to study effects of drying methods on the tasty compounds of Pleurotus eryngii, a common commercial edible fungus. In order to maximally maintain the taste of P. eryngii, several different drying methods, including hot air, vacuum, microwave, freeze drying and naturally air-drying, were compared. Results showed that freeze drying and hot air were capable of the conservation of the taste compounds maximally in P. eryngii, followed by natural air drying and vacuum, while microwave drying was not suitable for P. eryngii due to the loss of taste compounds. Moreover, concentrations of free amino acids in freeze drying were significantly reduced, so as to 5'-nucleotides in hot air drying. In addition, the umami concentration of the sample using hot air dry was significantly (p

Far infrared radiation (FIR) and hot air drying (HA) were applied to unpolished and polished pigmented rice varieties. Ferulic acid is a major phenolic acid in pigmented rice, being three-fold greater in bound form than in soluble form. Overall, FIR increased total phenolic and flavonoid contents, anthocyanin, tocopherols as well as antioxidant capacity, whereas the opposite results were observed for HA in all samples. Gallic, and ferulic acids were significantly (p 0.05) increased in FIR dried samples. Quercetin content was significantly increased in unpolished rice dried by FIR and HA. Cyanidin-3-glucoside was greatly increased by FIR. Amino acids were decreased less by HA than did FIR. Our findings suggest that HA and FIR may have a significant effect on the internal structure of the grain, which may increase the yield of extraction of some components, including the bioactives.

Because black rice is rich in antioxidants, appropriate methods of post-harvest treatment are necessary for maintaining these bioactive phytochemicals. Drying methods, storage temperatures, storage duration, and packaging methods affected the contents of some bioactive compounds in the two varieties of Thai black rice used in this research. Sun drying reduces the loss of anthocyanins and γ-oryzanols more than does hot air drying. Glutinous black rice stored as paddy at cool room temperature retains more anthocyanins, γ-oryzanols, and vitamin E than does paddy stored at room temperature. Nylon/LLDPE pouches containing N2 are the most suitable packaging for preserving the key aroma compound 2-acetyl-1-pyrroline (2AP), total phenolic, and anthocyanin contents of unpolished aromatic black rice. These pouches also retard the formation of some common off-flavor compounds.

White cabbage (Brassica oleracea L. var. capitata) is an important source of dietary fibre (DF) and various bioactive compounds, which are claimed to possess antioxidant and anticarcinogenic activities. Sulforaphane, one of the most potent food-derived anticarcinogens, is a hydrolysis product of glucosinolates, which are abundant in Brassica vegetables. As the formation of sulforaphane is via enzymatic reactions and since the compound is heat sensitive, processing temperature is of importance. In this study the effect of hot air drying temperature (40–70 °C) on the evolution of sulforaphane in cabbage during drying was investigated; outer leaves of cabbage, which are discarded and normally considered as waste, were used. The retention of sulforaphane in the finally dried DF powder was also determined. The results showed that the formation of sulforaphane occurred when the cabbage temperature during drying was in the range of 25–53.5 °C and thermal degradation took place once the cabbage temperature exceeded this range. A semi-empirical heat transfer and kinetic model was proposed to predict the evolution of sulforaphane during drying. Drying at 60 °C was suggested as an optimum condition to obtain the highest retention of sulforaphane in cabbage DF powder.

The present work was aimed at studying the effects of drying methods and conditions (i.e., ambient drying, hot air drying at 40 °C, vacuum drying and low-pressure superheated steam drying within the temperature range of 70–90 °C at an absolute pressure of 10 kPa), as well as the concentration of Indian gooseberry extract, (added to edible chitosan film-forming solution as a natural antioxidant, at concentrations of 1, 2 and 3/100 g), on the residual total phenolic content (TPC) of the films. The swelling and release behaviour of TPC from the films were also studied. Drying methods and conditions were found to have significant effects on the percentage of residual TPC. The release characteristics, swelling and functional group interaction of the antioxidant films, as assessed by Fourier-transform infrared (FTIR) spectroscopy, were found to be affected by the drying methods and conditions, as well as the concentration of the Indian gooseberry extract.

The mulberry ( Morus alba L.) leaf is a promising dietary source of antioxidants such as quercetin due to its relatively high content of that compound. We investigated effects of an air-drying process on the antioxidant capacity and stability of antioxidant polyphenolic compounds in mulberry leaves. Main compounds playing a central role in antioxidant activities in mulberry leaves are quercetin glycosides and chlorogenic acid. Raw mulberry leaves were air-dried at various temperatures, and antioxidant activity using DPPH radical scavenging assay and levels of antioxidant compounds were measured. DPPH radical scavenging activity and levels of polyphenolic compounds in mulberry leaves air-dried at 60 °C or below were not significantly different from those of freeze-dried mulberry leaves, whereas both values in mulberry leaves air-dried at 70 °C and over decreased significantly. These results indicate that strict temperature control is important in the production of mulberry leaf products to maintain antioxidant activity and levels of polyphenolic compounds.

The effect of different drying methods on steroidal saponins, furostanol and spirostanol glycosides, in Dioscorea pseudojaponica Yamamoto, were studied. The yams were either steam-blanched or not blanched before drying. Results showed that solar and shaded drying without prior blanching would cause significant changes of yam saponins; hot air drying caused slight variation, and other drying methods showed almost no change. A similar phenomenon was observed in a model system containing crude yam saponin extract; it indicated that higher temperature and light exposure had very little effect on the stability of yam saponins during drying. On the other hand, the endogenous glucosidase in yam might play an important role in altering the saponin structures during drying. This was confirmed by a model experiment; a crude furostanol glycoside 26- O - β -glucosidase prepared from yam was shown to remove the glucose at position C-26 of the furostanol glycoside structure and change it to the respective spirostanol glycoside.

Hot air drying and microwave drying were applied to dry fish fillets made of grass carp (Ctenopharyngodon idellus), and the correlative influences on nutritional and odorous properties were evaluated by proximate composition, protein solubility, amino acid composition, fatty acid composition, peroxide value, anisidine value, and odour evaluation. Drying resulted in a significant increase of protein but reduced fat content. There was lack of negative influence of the drying process on the amino acid composition of grass carp fillets. Both saturated and monounsaturated fatty acid contents decreased, while polyunsaturated fatty acids increased by an average of 23.8% after drying. Microwave-dried samples showed lower fat loss, higher protein solubility, and lower anisidine values than hot air-dried samples. There was no significant difference in odour quality between hot air-dried and microwave-dried samples. The present study provides a possible application of microwave drying as an efficient drying process for fish fillets.

Banana puree was dehydrated by using three different drying methods: vacuum belt drying (VBD), freeze-drying (FD) and air-drying (AD) to produce banana powder. Volatiles were extracted from dried banana powder with solid phase micro-extraction (SPME), and separated and identified by gas chromatography–mass spectrometry (GC–MS). SAS (statistical analysis system) was used to evaluate the contribution of the main volatiles. Esters play the most important role in banana powder aroma. The main components detected in banana powder which are responsible for its fruity odor were 3-methylbutanoic acid 3-methylbutyl ester, 3-methylbutyl acetate and butanoic acid 3-methylbutyl ester. Most of the alcohols identified in banana powder were enols and some were of the long chain type. Eugenol and elemicin which give the product its typical mellow aromas were also identified. Alkyls, alkene and alkyne constituted the minor components in banana powder. Basing on the principal component analysis of statistical analysis system, it can be inferred that the preferred method for producing banana powder with the optimum aroma is FD, followed by VBD and then AD.

Volatile compounds are important factors that affect the flavor quality of Flammulina velutipes, but the changes occurring during hot air drying is still unclear. To clarify the dynamic changes of flavor components during hot air drying, comprehensive flavor characterization and volatile compounds of F. velutipes were evaluated using electronic nose technology and headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS), respectively. Results showed that volatile components in F. velutipes significantly changed during hot air drying according to the principal component analysis and radar fingerprint chart of electronic nose. Volatile compounds of fresh F. velutipes consisted mainly of ketones, aldehydes and alcohols, and 3-octanone was the dominant compound. Drying process could significantly decrease the relative content of ketones and promoted the generation of alcohols, acids, and esters, which became the main volatile compounds of dried F. velutipes. These may provide a theoretical basis for the formation mechanism of flavor substances in dried F. velutipes.

Foams were prepared from starfruit ( Averrhoa carambola L. ) puree by adding various concentrations of methocel. Overrun and density of the foams from various concentrations of methocel were compared. Relative stability of the foam was determined by comparing amounts of juice separated from foam at 70°C. Drying rates at two drying temperatures (70 and 90°C) were also compared. Quality of the dry and reconstituted powder was evaluated with simple sensory evaluation and Hunterlab instrument. Overrun and stability of foams increased with increasing methocel concentration until maximum value was obtained at a methocel concentration of 0.4% w/w. Falling rate was observed for foam dried at both temperatures. Drying time could be shortened by as much as 30 min when drying temperature was increased from 70 to 90°C. However, obvious colour and flavour changes were observed in the product dried at 90°C. This study has indicated that, under the experimental conditions employed, reasonably good powder characteristics can be obtained.

The extent and nature of denaturation of whey protein isolate (WPI) in convective air drying environments was measured and analysed using single droplet drying. A custom-built, single droplet drying instrument was used for this purpose. Single droplets having 5 ± 0.1 μl volume (initial droplet diameter 1.5 ± 0.1 mm) containing 10% (w/v) WPI were dried at air temperatures of 45, 65 and 80 °C for 600 s at constant air velocity of 0.5 m/s. The extent and nature of denaturation of WPI in isothermal heat treatment processes was measured at 65 and 80 °C for 600 s and compared with those obtained from convective air drying. The extent of denaturation of WPI in a high hydrostatic pressure environment (600 MPa for 600 s) was also determined. The results showed that at the end of 600 s of convective drying at 65 °C the denaturation of WPI was 68.3%, while it was only 10.8% during isothermal heat treatment at the same medium temperature. When the medium temperature was maintained at 80 °C, the denaturation loss of WPI was 90.0% and 68.7% during isothermal heat treatment and convective drying, respectively. The bovine serum albumin (BSA) fraction of WPI was found to be more stable in the convective drying conditions than β-lactoglobulin and α-lactalbumin, especially at longer drying times. The extent of denaturation of WPI in convective air drying (65 and 80 °C) and isotheral heat treatment (80 °C) for 600 s was found to be higher than its denaturation in a high hydrostatic pressure environment at ambient temperature (600 MPa for 600 s).

Volatiles in Rabdosia serra were investigated by headspace solid phase microextraction (HS-SPME) and simultaneous-distillation extraction (SDE). The HS-SPME technique was previously evaluated to optimise sampling conditions. A total of 56 and 48 compounds including alcohols, aldehydes, hydrocarbons, ketones, carboxylic acid, ester, and aromatics were identified in leaf and stem by optimised HS-SPME method (CAR/PDMS fibre; incubation time, 10 min; extraction temperature, 50°C; extraction time, 40 min), respectively. 1-Octen-3-ol and (2E)-hexenal had significant contribution to R. serra aroma. Cluster analysis indicated that leaf and stem exhibited different volatile diversity. Air drying was favourable for the retention of the volatiles, while freeze- and sun-drying led to the loss of volatiles. SDE method preferred to the analysis of compounds with low volatility including fatty acids and esters. HS-SPME was a useful technique for the analysis of readily volatile components for the characteristics of R. serra aroma.