Quality of restructured cookies made from old stalks of Asparagus officinalis using various drying methods

The restructured crisp cookies were made from the old stalks of Asparagus officinalis. Temperature distribution, expansion ratio, moisture content, and color were measured to evaluate the drying uniformity of the cookies by applying pulse-spouted microwave-assisted vacuum drying (PSMVD) and microwave-assisted vacuum drying (MVD). Besides, bulk density, expansion ratio, microstructure, and textural properties were used to compare the products’ quality obtained by three different drying methods including vacuum drying, MVD, and PSMVD. Results showed that the products dried by PSMVD were more uniform compared to those samples dried by MVD. The pulse-spouted mode in drying chamber substantively improved the microwave-vacuum-dried products’ quality, drying uniformity, and drying characteristics.     

Effect of three drying methods on the drying characteristics and quality of okra

The objective of this study was to compare the drying characteristics and quality of dried okra obtained by vacuum freeze drying (VFD), microwave vacuum drying (MVD), and pulse-spouted microwave vacuum drying (PSMVD). The quality parameters include color (L*, a*, and b*), texture (hardness and fracturability), shrinkage ratio (SR), nutrient retention (chlorophyll, flavonoids, and vitamin C), and sensory score was investigated. Vacuum freeze drying maximally preserved the original properties of samples. And the samples dried by PSMVD showed higher quality and more uniformity compared to MVD. Considering of all aspects comprehensively, such as cost-effectiveness, practicability, and scale-up, PSMVD was a promising technique which would match results obtained by vacuum freeze drying.     

Drying kinetics and product quality of green soybean under different microwave drying methods

The objective of this study was to investigate the effect of different microwave drying techniques on the drying kinetics and product quality of dried green soybean. Experiments were conducted using microwave vacuum drying (MVD), pulse-spouted vacuum microwave drying (PSMVD), pulse-spouted microwave drying (PSMD), and microwave freeze drying (MFD). Parameters of apparent density, color, processing temperature, expansion ratio, rehydration ratio, texture, and microstructure of the dried products were determined. The results showed that the MFD green soybean had a small change on bright color, compared with the fresh samples, but the drying time was the longest among the four methods. The bright color value of PSMVD/PSMD/MVD, respectively, was 79.77, 71.43, and 55.45, and drying time of them was slightly different. The PSMVD/PSMD showed advantages over MVD by improving the product quality.     

Design and performance evaluation of a pilot-scale pulsed vacuum infrared drying (PVID) system for drying of berries

Abstract

The objective of current work was to develop a new pilot-scale pulsed vacuum infrared drying (PVID) system for the drying of berries. The system design and drying performance evaluation for grape and goji berries are reported here. The PVID system consisted of three major sections, including infrared heating section, vacuum section, and a controlling section. Electrical infrared (IR) emitter was made with carbon fiber sheet at the thickness of 2–4?mm, which emitted IR wavelength of 1–30?μm. The control system was used to achieve paused pressure by switching the drying chamber pressure between atmospheric pressure (101?kPa) and vacuum (3–10?kPa) successively and maintaining the pressure for different time periods. Grapes and goji berries were dried in a single layer at three different temperatures (55, 65, and 75?°C) with an atmospheric duration ranging from 1 to 12?min and vacuum duration from 10?min to constant vacuum. The drying characteristic and quality of PVID dried berries were investigated and compared with that of hot air (HA) dried berries. Results showed that the IR heating temperature, atmospheric duration, and vacuum duration had significant effects (p?<?.05) on the drying time. The optimum drying conditions for grapes and goji berries were IR heating at 65?°C, vacuum duration of 15?min, and atmospheric duration of 4 and 2?min, respectively. The corresponding drying time is nearly 720?min for grapes, and 450?min for goji berries. The PVID dried grapes and goji berries had more attractive color than that of HA dried ones. These findings demonstrated that PVID should be a promising method to produce high-quality dried berries. This study laid a good foundation for scaling up the technology in the future.     

Effect of Four Drying Methods on the Quality of Osmotically Dehydrated Cranberries

Abstract

Partially dehydrated cranberries (osmotically dehydrated) were dried to low water contents using one of following four methods: hot air drying; microwave-assisted convective drying; freeze-drying; and vacuum drying. Quality evaluation was performed on all samples, including sensory evaluation (appearance and taste), texture, color, water activity, and rehydration ratio. Hot air drying produced dried cranberries with the best visual appearance while freeze-dried cranberries had the highest rehydration ratio. The other methods presented similar rehydration ratios. There was no significant difference in color measurements and water activity. Few differences in texture were found, except for freeze-dried cranberries, which had a lower toughness compared to the other drying methods including commercially available dried cranberries. Microwave-assisted to hot air drying rate ratios increased as the moisture content decreased.     

Influence of number of puffing times on physicochemical,color, texture,and microstructure of explosion puffing dried apple chips

The impact of number of puffing times during explosion puffing drying (EPD) on drying characteristics and qualities of apple chips was studied. Physicochemical characteristics, antioxidant capacity, color, texture, expansion ratio, rehydration ratio, hydroscopicity, and microstructure of apple chips dried by EPD with 0 (vacuum drying, VD), 1, 3, 5, 7, and 9 puffing times were analyzed. The apple chips dried by EPD with 3 and 5 puffing times exhibited better color (ΔE 7.27–7.70) and texture (hardness 40.5–40.8 N, crispness 8.8–9.3 N/mm), as well as higher expansion ratio (104.4–109.7%) compared to VD and EPD with fewer or more puffing times. The samples dried with 3 and 5 puffing times also showed relatively higher rehydration ratio and hygroscopicity, and acceptable retention of total phenolic content (0.32–0.37 mg/g) and ascorbic acid content (1.66–1.89 mg/100 g), as well as considerable antioxidant abilities (DPPH 79.45–81.17 AEAC µM/g, FRAP 66.54–68.25 TEAC µM/g, ABTS 73.36–79.21 TEAC µM/g) compared to VD dried samples. In conclusion, experiments with apple chips indicated that EPD drying with 3 to 5 puffing times yielded superior overall quality than that with more or fewer puffing times.     

Dehydration of Concentrated Ganoderma lucidum Extraction by Combined Microwave-Vacuum and Conventional Vacuum Drying

Combination of microwave-vacuum drying and conventional vacuum drying was investigated as a potential method for drying concentrated Ganoderma lucidum extraction. The Ganoderma lucidum was extracted by hot water (60–65°C) and then concentrated to moisture of about 70% (wet basis) in a rising-film evaporator. The concentrated sample was dried by microwave-vacuum until the moisture content reached 10% (wet basis), and then by conventional vacuum drying at the temperature of 55–60°C to final moisture content about 6% (wet basis). The retention of polysaccharide and triterpenes of Ganoderma lucidum dried by this method were evaluated and compared with those dried by freeze drying and conventional vacuum drying alone. The comparison showed that the quality of extraction dried by the current method was close to that of freeze-dried extraction and much better than that of conventional vacuum-dried ones.     

Pulsed vacuum drying (PVD) technology improves drying efficiency and quality of Poria cubes

The objective of this research was to examine the drying characteristics of pulsed vacuum drying (PVD) system as an alternative drying technology for a functional food—Poria cocos. Poria cubes in thin layer were dried at different temperatures (55, 65, and 75°C), vacuum duration (5, 15, and 25?min), and atmospheric pressure duration (4, 8, and 12?min) to evaluate the operating conditions on the drying kinetics and quality attributes of P. cocos. The quality attributes included volume shrinkage ratio, firmness, water-soluble polysaccharide content. Volume shrinkage ratio was determined by image processing technology and analyzed by Bigot’s curves. The material internal temperature was also recorded during the whole drying process. Considering the drying rate and quality attributes, drying temperature of 65°C, vacuum pressure duration of 15?min, and atmospheric pressure duration of 4?min were proposed as the most favorable drying conditions for drying Poria cubes. The current work indicates PVD is a promising technology for P. cocos drying as it not only enhances the drying process but also improves the quality attributes of it.     

The effect of freezing on the hot air and microwave vacuum drying kinetics and texture of whole cranberries

Abstract

The aim of this study was to evaluate the effect of convective and cryogenic freezing, hot air convective drying (HACD) at 60, 70, 80, and 90?°C and microwave vacuum drying (MWVD) at 100, 150, 200, 300, 450, and 500?W on the drying kinetics and texture of whole cranberries. Effective moisture diffusivities and drying rates were higher, whereas drying times were shorter for the samples dried by MWVD compared with the samples processed by HACD. The drying kinetics of cranberries during MWVD was discussed based on the hypothesis postulating that changes in the drying rate of cranberries during MWVD can be explained by and correlated with changes in the pressure gradient on material surface. Cranberries processed by MWVD were characterized by significantly greater hardness, gumminess, and chewiness in comparison with HACD samples. MWVD was found to be an effective method for producing dried snacks characterized by hard and crispy texture and considerable resistance to stress associated with manufacturing, packaging, storage, and delivery. HACD produced brittle fruit that were difficult to store and transport and were not fully suitable for direct consumption. Convective freezing before MWVD improved the overall appearance of cranberries, whereas cryogenic freezing combined with high temperature HACD adversely influenced the drying rate and produced dried cranberries with suboptimal overall appearance.     

Pulsed vacuum drying (PVD) of wolfberry: Drying kinetics and quality attributes

The effects of drying temperature (50, 53, 56, 59, 62, and 65°C) and pulsed vacuum ratio defined as the vacuum pressure duration versus atmosphere pressure duration (3:3, 6:6, 9:2, 12:5, 15:1, 18:4?min/min) on pulsed vacuum drying (PVD) characteristics and quality attributes of wolfberry in terms of polysaccharide content, color parameters (L^*, a^*, b^*, ΔE, and C), rehydration ratio and microstructure were investigated. Results revealed that appropriate PVD can reduce drying time by 73.2% compared to hot air drying at the same drying temperature. The moisture effective diffusivity (D_eff) ranged from 5.23?×?10^?10 to 9.73?×?10^?10?m²/s, calculated using the Weibull distribution model. The polysaccharide content, L^* (lightness), a^* (redness/greenness) of the PVD products were higher than those of the hot air-dried samples at the same drying temperature. The total color difference (ΔE) and color intensity (C) of PVD samples were close to those of the fresh ones. The retention rate of total polysaccharide content of PVD samples was about 49–77%, which was significantly higher than 30% of the hot air-dried samples. The surface of PVD wolfberry was highly porous, which may enhance moisture transfer during drying as well as rehydration processes. The results of current work indicate that PVD is a promising technology for wolfberry process, for the reason that PVD can reduce drying time significantly as well as enhance the quality attributes in terms of the total polysaccharide content, color parameters and rehydration ratio.     

Drying Characteristics and Quality of Restructured Wild Cabbage Chips Processed Using Different Drying Methods

The drying characteristics of restructured wild cabbage chips dried using microwave vacuum (MVD), hot air (AD), and microwave freeze drying (MFD) were compared. Some of the key quality parameters of restructured wild cabbage chips such as fracturability and color and sensory characteristics were measured. Results showed that the drying time was reduced with the increase of microwave power (MVD/MFD) and in the case of air drying by the temperature (AD). Drying time was the shortest in the MVD process. Optimal quality of dried chips was obtained with the MFD process at a microwave power level 2.0 W/g.     

Production of dried ivy gourd sheet as a health snack

Ivy gourd (Coccinia grandis) has recently been recognized as a rich source of β-carotene. To add value to the fresh leaves a process to produce dried ivy gourd sheet as a health snack was the aim of this study. The effects of pretreatment, i.e., blanching in NaCl solution (0-3% w/v), and drying methods, i.e., hot air drying and vacuum drying at 60-80 °C, on the drying characteristics and quality, viz. colour, texture and β-carotene content of dried ivy gourd sheet were investigated. The results showed that dried sheet pretreated by brine blanching and vacuum drying resulted in better retention of colour and β-carotene as well as texture of the dried sheet as compared to the dried untreated and dried water blanched samples. Higher drying temperature also resulted in higher β-carotene retention due to shorter drying time.     

Red pepper (Capsicum annuum L.) drying: Effects of different drying methods on drying kinetics,physicochemical properties,antioxidant capacity,and microstructure

Results of an experimental study are presented and discussed for pulsed vacuum drying (PVD), infrared-assisted hot air-drying (IR-HAD), and hot air-drying (HAD) on drying kinetics, physicochemical properties (surface color, nonenzyme browning index, red pigments, rehydration ratio, water holding capacity, and ascorbic acid), antioxidant capacity (ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity), and microstructure of red pepper. As expected, the drying time decreased with an increase in drying air temperature, IR-HAD needed the shortest drying time, followed by HAD and PVD. The effective moisture diffusivity (D_eff) of red pepper under PVD, HAD, and IR-HAD was computed to be in the range 1.33–5.83?×?10^?10, 1.38–6.87?×?10^?10, and 1.75–8.97?×?10^?10 m²/s, respectively. PVD provided superior physicochemical properties of dried red pepper compared to samples dried by HAD and IR-HAD. In detail, PVD yielded higher rehydration ratio, water holding capacity, red pigment and ascorbic acid content, brighter color, lower nonenzyme browning index, and comparable antioxidant capacity compared to samples dried by HAD and IR-HAD at the same drying temperature. Furthermore, PVD promoted the formation of a more porous structure, while HAD and IR-HAD yielded less porous structure. The current findings indicate that PVD drying has the potential to produce high-quality dried red pepper on commercial scale.     

Study on quality attributes and drying kinetics of instant parboiled rice fortified with turmeric using hot air and microwave-assisted hot air drying

Abstract

This study investigated the quality and drying kinetics of instant parboiled rice fortified with turmeric (IPRFT) by using hot air (HA) and microwave-assisted hot air (MWHA) drying. The cooked long grain parboiled rice (LGPR) fortified with turmeric was dried with HA at temperatures of 65, 80, 95, and 110?°C. The microwave power density of 0.588 Wg^?1 was incorporated for drying with MWHA. Drying was performed until the dried IPRFT reached 16% (d.b.) of moisture content. The quality of the dried IPRFT was evaluated in terms of color, total phenolics content (TPC), total antioxidant capacity (TAC), rehydration ratio, volume expansion ratio, texture and microstructure. The results showed that the incorporation of microwave power with HA drying helped to reduce the drying time by 50% compared to conventional HA drying. A prediction of the moisture ratio by using the Page model provided the best R² and RMSE in drying kinetics. The drying conditions had small effects on the color, TPC, TAC, and microstructure of the dried IPFRT. The rehydration ratio, volume expansion ratio and texture of the rehydrated IPFRT showed minimal variations from changes in the drying conditions. The TPC and TAC of the dried IPRFT clearly increased compared to the TPC and TAC of the initial LGPR.     

Effect of preconditioning on physicochemical,microstructural, and sensory quality of vacuum-fried jackfruit chips

The effect of preconditioning steps in terms of either freezing or partial drying on the quality of vacuum-fried jackfruit (JF) chips was evaluated. Prepartial drying process of the JF bulb slices resulted in the lowest moisture content in the vacuum-fried chips. The rate of oil uptake by JF bulb slices was found to be almost same in control and prefrozen samples during frying process. However, prepartial drying of slices resulted in a slower rate of oil absorption. The total carotenoid content was found to be 1.81, 0.96, and 1.87?mg/100?g (db) in control, prepartially dried and prefrozen JF chips, respectively. The Hunter L-value of control, prepartially dried, and prefrozen chips was found to be 52.3, 39.4, and 48.5, respectively. The a-value was found to increase, whereas the b-value decreased during vacuum frying in all the JF chip samples, irrespective of preconditioning type adopted. Prefrozen JF chips were found to have highest crispy texture in terms of lowest instrumental breaking force compared to the control and prepartially dried JF chips. Prefrozen JF chips were found to have lowest bulk density and highest porosity. The micrograph of prepartially dried JF chips depicted dense and shriveled structure, whereas a porous structure in prefrozen chips. The preconditioning protocols of partial drying and freezing were found to affect the overall sensory acceptability scores significantly (P?相似文献   

Freeze drying and vacuum impregnating characteristics of Nostoc sphaeroides Kützing

ABSTRACT

Nostoc sphaeroides Kützing (N. sphaeroides) is a kind of edible algae widely growing in China. The paper is aimed at developing a novel snack food of N. sphaeroides using vacuum impregnation. The samples from freeze drying (FD) have large volume and loose structure, which were found suitable for processing. With nuclear magnetic resonance and imaging, the water signal of N. sphaeroides was measured in FD, and different drying-stage raw N. sphaeroides were selected to impregnate by different solutions, when the products’ impregnated mass, water activity, and flavor difference were analyzed. Results indicate that the water distribution in FD was uniform. Sucrose impregnated product was stable with large impregnated mass and low water activity, whereas trehalose impregnated product was easy to separate from the solution with low sweetness. For the products with the raw N. sphaeroides dried for 9 and 12?h, no obvious difference was found in water activity and flavor. Result shows that N. sphaeroides dehydrated for 9?h in FD is suitable for vacuum impregnation, and different impregnated products are acceptable from the point of view of flavor and storage stability.     

A Combination of Freeze Drying and Microwave Vacuum Drying of Duck Egg White Protein Powders

High energy consumption during freeze drying (FD) is a major concern that limits its application on common food product manufacturing. In this research, fresh duck egg white protein (FDEWP) powder and desalted duck egg white protein (DDEWP) powder were obtained by a combined two-stage tandem drying technologies (FD and microwave–vacuum drying [MVD]) in order to reduce energy consumption while maintaining good product quality. The results showed that the drying time for the FDEWP and DDEWP powders was significantly decreased by FD + MVD compared to those obtained by the FD-only process. The FDEWP powders dried by FD + MVD had a better color (higher L* and lower b*), lower apparent density, and lower foaming stability but higher emulsifying index than those dried by FD only. The DDEWP powder dried by FD + MVD had a product quality similar to that of FDEWP powder, suggesting that the DDEWP powder could be widely used as a food ingredient.     

Ultrasound-assisted osmotic process on quality of microwave vacuum drying sweet potato

The effects of pretreatment before microwave vacuum drying (MVD) on texture, color, expansion, rehydration, drying rate, microstructure, sensory evaluation, and other properties of sweet potato were investigated in this study. The pretreatment consisted in five processing conditions, using blanching; osmotic dehydration at 35°Brix of sucrose (OD); ultrasound in distilled water (US); ultrasound in distilled water before osmotic dehydration (US?+?OD), and ultrasound-assisted osmotic dehydration (USOD). Pretreatments of sweet potato before MVD have shown success in reducing drying time with US treatment relatively more effective regarding drying time than other treatments. Compared with other treatments, US showed the highest rehydration ratio values. The osmotic group pretreatment exhibited a pronounced effect on water loss and solid gain, improved the color, aroma, and taste of dried sweet potato, whereas sucrose impregnation resulted in a hard texture observed with OD sample. USOD samples had a higher expansion ratio, lower hardness and color difference values, appeared less cell damaged, and recorded better overall quality than the other samples. There was a slight difference between USOD and US?+?OD samples. Combining osmotic dehydration with ultrasound as a pretreatment can significantly accelerate the heat transfer rate, reducing the dried time accordingly and increasing energy efficiency.     

Controlling the drying process in vacuum foam drying under low vacuum conditions by inducing foaming by needle stimulation of the solution

Abstract

Vacuum foam drying is a promising drying technique but an extremely high vacuum is needed to achieve “foaming.” The findings reported herein show that, when a solution is partially vacuum-dried to 0.05–2?g-solvent/g-dry matter (initial drying) and the solution is then punctured with a steel needle (needle stimulation), vacuum drying resumes as a result of the solution foaming, even under conditions of an insufficient vacuum (ca. 1,000?Pa) where foaming is minimal. Methanol, ethanol, and isopropanol were used as solvents, and sugar and different molecular weight polyvinylpyrrolidone were employed as solutes. The results indicate that needle puncturing introduces minute bubbles, which then triggers foaming.     

Scope of vacuum press drying for fast removal of moisture below fiber saturation point

Studies were taken up on 25 mm thick samples of Tectona grandis to understand its drying behavior under vacuum press drying. Five different vacuum level–temperature combinations were used in the study to observe the moisture reductions achieved. The results were analyzed to understand which combination gave maximum moisture content reduction from two moisture content ranges: one above and the other below the fiber saturation point of the species. It was found that the samples could be dried to less than 13% moisture content levels from about 25% moisture content levels effectively in just two runs approximately lasting 7 h each. More interestingly, the moisture removal by this method was found more effective when samples were seasoned from initial moisture content levels below the fiber saturation point. This study will pave way for developing schedules for T. grandis for faster and degrade-free seasoning.