Dehydration of Garlic Slices by Combined Microwave-Vacuum and Air Drying

Abstract

Combination of microwave-vacuum drying and air drying was investigated as a potential mean for drying garlic slices. The sample was dried by microwave-vacuum until the moisture content reached 10% (wet basis), and then by conventional hot-air drying at the temperature of 45°C to final moisture content less than 5% (wet basis). Pungency, color, texture, and rehydration ratio of garlic slices dried by this method were evaluated and compared with those dried by freeze drying and conventional hot-air drying. The comparison showed that the quality of garlic slices dried by the current method was close to that of freeze dried garlic slices and much better than that of conventional hot-air dried ones. The lab microwave-vacuum dryer which the materials to be dried could be rotated in the cavity was developed by the authors.     

Dehydration of Garlic Slices by Combined Microwave-Vacuum and Air Drying

Combination of microwave-vacuum drying and air drying was investigated as a potential mean for drying garlic slices. The sample was dried by microwave-vacuum until the moisture content reached 10% (wet basis), and then by conventional hot-air drying at the temperature of 45°C to final moisture content less than 5% (wet basis). Pungency, color, texture, and rehydration ratio of garlic slices dried by this method were evaluated and compared with those dried by freeze drying and conventional hot-air drying. The comparison showed that the quality of garlic slices dried by the current method was close to that of freeze dried garlic slices and much better than that of conventional hot-air dried ones. The lab microwave-vacuum dryer which the materials to be dried could be rotated in the cavity was developed by the authors.     

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

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.     

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.     

Effects of Peeled and Unpeeled Garlic Cloves on the Changes of Drying Rate and Quality

Reducing moisture content as fast as possible, together with minimizing loss of quality, is important to food processing. To reach these objectives, experimental investigations were conducted to examine the effects of both peeled and unpeeled garlic cloves as well as operating parameters such as temperature and superficial velocity on the drying rate and quality of dried product. Peel resistance to moisture diffusion is considerably dominated and yields the longer drying time. Drying at high temperature shows the shrinkage of garlic clove to be lower than that at low temperature, whereas the product color is browner and the sizes of produced pores as revealed by scanning electron microscope are larger. The loss of volatile oil is insignificantly different among low- and high-temperature drying. The peel effect exhibits negative results on the product color, giving lower luminosity than the peeled sample, in particular at low temperature, because of longer drying time.     

Effect of Microwave-Vacuum Drying on the Carotenoids Retention of Carrot Slices and Chlorophyll Retention of Chinese Chive Leaves

Microwave-vacuum drying, and combined microwave-vacuum with air or vacuum drying were investigated as potential methods for drying green and high-carotenoid vegetables of Chinese chive leaves and carrot slices. The samples were dried by microwave-vacuum until the moisture content reached about 20% (wet basis), and then by conventional air drying at the temperature of 45-50°C or conventional vacuum drying at the temperature of 55-60°C or by continued microwave-vacuum drying at lower power level to final moisture content about 6% (wet basis). The carotenoid retention of carrot slices and chlorophyll retention of Chinese chive leaves, dried by these methods, was evaluated and compared with those dried by freeze-drying and conventional hot-air drying. The comparison showed that the carotenoid retention of carrot slices and chlorophyll retention of chive leaves, dried by the current methods, was very close to or even as much as those dried by freeze-drying and much better than those dried by conventional hot-air. Blanching was not necessary when using microwave-vacuum drying or combined microwave-vacuum with conventional hot-air drying or vacuum drying, because the activity of enzymes which were responsible for the degradation of color was greatly reduced with extremely rapid decreasing of moisture, and because oxygen was absent in microwave-vacuum drying.     

Effects of Peeled and Unpeeled Garlic Cloves on the Changes of Drying Rate and Quality

Reducing moisture content as fast as possible, together with minimizing loss of quality, is important to food processing. To reach these objectives, experimental investigations were conducted to examine the effects of both peeled and unpeeled garlic cloves as well as operating parameters such as temperature and superficial velocity on the drying rate and quality of dried product. Peel resistance to moisture diffusion is considerably dominated and yields the longer drying time. Drying at high temperature shows the shrinkage of garlic clove to be lower than that at low temperature, whereas the product color is browner and the sizes of produced pores as revealed by scanning electron microscope are larger. The loss of volatile oil is insignificantly different among low- and high-temperature drying. The peel effect exhibits negative results on the product color, giving lower luminosity than the peeled sample, in particular at low temperature, because of longer drying time.     

Effect of Drying Method on Gas Adsorption Characteristics of Carbon Gel Microspheres

Abstract

The effect of drying method used in the preparation of carbon gel microspheres was studied by comparing the porous properties of carbon cryogel microspheres (CCM) and carbon xerogel microspheres (CXM), which were respectively obtained using freeze drying and hot air drying. CCM were found to possess higher mesoporosity than CXM because freeze drying was effective to suppress the shrinkage of the mesopores during drying. On the other hand, the microporosity of the carbon gel microspheres was hardly influenced by not only the drying method but also the synthesis condition. Although the amounts of nitrogen and oxygen adsorbed were almost the same, the adsorption rate of nitrogen on both CCM and CXM possessing ultramicroporous surfaces was much larger than that of oxygen, which indicated the applicability of the carbon gel microspheres to adsorbents for pressure swing adsorption (PSA) of air. The relations between the temperature and the amount of oxygen adsorbed showed the adsorption characteristics of CCM and CXM as adsorbents for temperature swing adsorption (TSA) were almost the same.     

Freeze-Drying of Liposomes with Cryoprotectants and Its Effect on Retention Rate of Encapsulated Ftorafur and Vitamin A

In this article, the glass transition temperature (T_g) of liposomal suspensions, in which glucose, sucrose, mannitol, and trehalose are used as cryoprotectants, are measured by differential scanning calorimetry (DSC). The protective effect of the cryoprotectants added for liposomes during freeze-drying is investigated. Results show that the T_g of liposomal suspension with trehalose is the highest, while that with glucose is the lowest. Depending on the concentration, the vesicle size of liposomes with trehalose as cryoprotectant varies less, while the vesicle size of liposomes, with glucose as cryoprotectant varies over a wider range during the process of freeze-drying. Water-soluble ftorafur and lipid-soluble vitamin A encapsulated in liposomes were freeze-dried. The retention rates of the encapsulated pharmaceuticals inside the liposomes are measured with high performance liquid chromatography. The results indicate that the retention rate for liposomes with trehalose is the highest, and the leakage of the pharmaceutical material is less than that with glucose used as a cryoprotectant. Through a series of experimental studies, trehalose is identified as a better cryoprotectant. An optimized freeze-drying procedure for liposomes is presented.     

Freeze-Drying of Liposomes with Cryoprotectants and Its Effect on Retention Rate of Encapsulated Ftorafur and Vitamin A

Abstract

In this article, the glass transition temperature (T _g ) of liposomal suspensions, in which glucose, sucrose, mannitol, and trehalose are used as cryoprotectants, are measured by differential scanning calorimetry (DSC). The protective effect of the cryoprotectants added for liposomes during freeze-drying is investigated. Results show that the T _g of liposomal suspension with trehalose is the highest, while that with glucose is the lowest. Depending on the concentration, the vesicle size of liposomes with trehalose as cryoprotectant varies less, while the vesicle size of liposomes, with glucose as cryoprotectant varies over a wider range during the process of freeze-drying. Water-soluble ftorafur and lipid-soluble vitamin A encapsulated in liposomes were freeze-dried. The retention rates of the encapsulated pharmaceuticals inside the liposomes are measured with high performance liquid chromatography. The results indicate that the retention rate for liposomes with trehalose is the highest, and the leakage of the pharmaceutical material is less than that with glucose used as a cryoprotectant. Through a series of experimental studies, trehalose is identified as a better cryoprotectant. An optimized freeze-drying procedure for liposomes is presented.     

Drying Kinetics and Antioxidant Phytochemicals Retention of Salak Fruit under Different Drying and Pretreatment Conditions

Kinetics of hot air drying and heat pump drying were studied by performing various drying trials on salak slices. Isothermal drying trials were conducted in hot air drying and heat pump drying at a temperature range of 40–90°C and 26–37°C, respectively. Intermittent drying trials were carried out in heat pump drying with two different modes: periodic heat air flow supply and step-up air temperature. It was observed that the effects of relative humidity and air velocity on drying rate were significant when moisture content in salak slices was high, whereas the effects of temperature prevailed when the moisture content was low. As such, it was proposed that drying conditions should be manipulated according to the moisture transport mechanisms at different stages of drying in order to optimize the intermittent drying and improve the product quality. Generally, loss of ascorbic acid during drying was attributed to thermal degradation and enzymatic oxidation, whereas the loss of phenolic compounds was mainly due to thermal degradation. Experimental results showed that heat pump drying with low-temperature dehumidified air not only enhanced the drying kinetics but produced a stable final product. Heat pump–dried samples retained a high concentration of ascorbic acid and total phenolic compounds when an appropriate drying mode was selected.     

Review: cardiovascular effect of garlic (Allium sativum)

Garlic has been used for centuries, and even nowadays is part of popular medicine in many cultures. New data have increased the interest in garlic and its role in normalization and treatment of cardiovascular disease risk factors. Recent studies have shown the complex composition of garlic, containing many compounds, that present potential positive effect in the field of health. The aim of the present paper was to review results of some studies that have found a relationship between garlic and cardiovascular diseases. From some of them it can be summarized that garlic can normalize plasma lipid, check lipid peroxidation, stimulate fibrinolytic activity, inhibit platelet aggregation, smooth the thickening and structural changes of artery wall related to aging and atherosclerosis, and decrease blood pressure. However, some other studies do not support these benefits. The positive effects found have promoted many study projects, nevertheless, the extract lability and the lack of result consensus call for a moderate consumption of garlic and garlic extracts. The composition variation due to gathering and aging together with the changes occurring in canning and industrial treatment makes necessary the application of some norms in the production and consumption of this functional food in order to guarantee its use in adequate form and doses.     

Fatty acid composition of garlic (Allium sativum Linnaeus) lipids

Chloroform-methanol extracted lipids of garlic (Allium sativum Linnaeus) amounted to 0.6% on a dry weight basis. Fractionation by silicic acid column chromatography showed that garlic lipids comprise 62.6% neutral lipids 14.0% glycolipids and 23.4% phospholipids. Fatty acid compositions of total lipids and component lipid fractions were determined.     

Effect of Mode of Drying on Microstructure of Potato

Potato v. Irga was subjected to blanching, and thereafter was dried by convection, puff-drying, and freeze-drying. Microstructure of raw, blanched, and dried tissue was analyzed under the light microscope using computer image analysis. It was found that the tissue of the investigated variety is built up from cells much smaller than those described in literature for other cultivars. Blanching caused starch gelatinization and increase of cross-sectional area of cells. There was no evidence of broken cell walls. Convective drying resulted in cell shrinkage and some breaking of cell walls. It was estimated that some 12% of cells lost integrity during drying. Limited disintegration of the tissue caused by convective drying is attributed to small size of cells, large contact area, and high cohesive forces between cells. Puff-drying damaged the tissue much more than the convective drying. The most devastating to tissue microstructure was freeze-drying, probably freezing per se.     

Genome-Wide Identification and Characterization of KNOTTED-Like Homeobox (KNOX) Homologs in Garlic (Allium sativum L.) and Their Expression Profilings Responding to Exogenous Cytokinin and Gibberellin

Garlic (Allium sativum L.) is an important vegetable and is cultivated and consumed worldwide for its economic and medicinal values. Garlic cloves, the major reproductive and edible organs, are derived from the axillary meristems. KNOTTED-like homeobox (KNOX) proteins, such as SHOOT MERISTEM-LESS (STM), play important roles in axillary meristem formation and development. However, the KNOX proteins in garlic are still poorly known. Here, 10 AsKNOX genes, scattered on 5 of the 8 chromosomes, were genome-wide identified and characterized based on the newly released garlic genome. The typical conserved domains of KNOX proteins were owned by all these 10 AsKNOX homologs, which were divided into two Classes (Class I and Class II) based on the phylogenetic analysis. Prediction and verification of the subcellular localizations revealed the diverse subcellular localization of these 10 AsKNOX proteins. Cis-element prediction, tissue expression analysis, and expression profilings in responding to exogenous GA₃ and 6-BA showed the potential involvement of AsKNOX genes in the gibberellin and cytokinin signaling pathways. Overall, the results of this work provided a better understanding of AsKNOX genes in garlic and laid an important foundation for their further functional studies.     

大蒜提取物沸腾干燥过程研究

采用系统设计和分析方法,通过对大蒜提取物的浓缩液在流化床干燥制粒机中的干燥制粒实验,得出了进风温度、进风量、喷雾空气压力、喷雾速度等主要参数的优化值;通过对FL-5型沸腾制粒机的改造,达到了改善颗粒的均匀度的目的.     

Drying of Mushroom Slices Using Hot Air Combined with an Electrohydrodynamic (EHD) Drying System

In this study, hot air combined with EHD drying is examined as an improved method for drying mushroom slices. The effects of three levels of voltage (17, 19, and 21 kV) and electrode gap (5, 6, and 7 cm) on the drying kinetics, time, effective water diffusion coefficient, and energy consumption of the EHD, pure hot air (provided within a chamber), and hot air combined with EHD drying systems were investigated. ANOVA showed that there were significant differences between EHD treatments and control (pure hot-air-drying treatment) for all of the investigated responses. Voltage and electrode gap factors had significant effects on all investigated responses. The results confirmed that the combination of EHD and hot air can significantly reduce the drying period, resulting in a greater effective water diffusion coefficient and drying rate and reduced energy consumption. As such, this technique offers a promising solution to the considerable energy consumption of the drying industry.     

Effect of garlic (Allium sativum linn) on serum lipoproteins and lipoprotein cholesterol levels in albino rats rendered hypercholesteremic by feeding cholesterol

The hypocholesteremic activity of garlic was tested by incorporating freeze-dried garlic powder at 0.5, 1.0, 2.0 and 3.0% levels in an atherogenic diet fed to rats. It was observed that 0.5 and 1.0% levels were not effective whereas the other 2 levels were. The group fed 2.0% garlic powder had much lower serum cholesterol level than the one fed 3%. The increased levels of low density lipoproteins (LDL) and LDL-cholesterol in rats fed the atherogenic diet were partly reversed in rats receiving a supplement of 2% garlic powder. On a cholesterol-containing diet, high density lipoproteins (HDL) and HDL-cholesterol levels were decreased. Inclusion of garlic powder in the atherogenic diet enhanced the percentage of HDL whereas no change was observed in HDL cholesterol levels. Commercial garlic pearls (equivalent to 0.15% garlic powder in the diet) produced a significant decrease in serum and liver cholesterol levels in rats fed the atherogenic diet. On the other hand, asafoetida at 1.5% level failed to reduce the serum cholesterol levels in the cholesterol-fed rats.     

Effect of Particle Structure on Quality Retention of Bio-Products During Thermal Drying

ABSTRACT

To study the influence of particle structure on quality retention of hioproducts during thermal drying, the porous particles formed of albumin and solid carriers were dried in a vibm-fluidized bed dryn at different inlet air temperatures and different initial bulk porosities. Equations to predict temperature and moishrre content of panicles as well as the kinetics of biomass degradation were developed. The particle bulk porosity was incorporated into concentration-dependent moisture diffusivity model to estimate the erect of particle structure on product quality. The analysis of both calculated and experimental results indicates that the more porous structure promotes moisture diffusion, increases drying rate and finally improves the quality retention of bio-products. An extensive literature survey on quality retention issues during thermal drylng has been done.