Retention of alkamides in dried Echinacea purpurea

Different drying methods, such as freeze-drying (FD), vacuum microwave drying (VMD), and air-drying (AD), were applied to fresh roots and leaves of Canadian-grown Echinacea purpurea to determine the optimal method for preserving alkamide levels. Using HPLC, six alkamide fractions (alkamides 1, 2, 3, 6a/6, 7, 8/9) were quantitated in dried roots, whereas four alkamide fractions (alkamides 1, 2, 3, 8/9) were measured in dried leaves. Different elution conditions used in HPLC for alkamide analysis did not affect the eluted fractions nor the quantitation of different alkamides. Individual alkamide concentrations in roots and leaves were affected by the drying methods used. To preserve higher levels of total alkamides, FD was found to be the best method, VMD was a superior method for drying roots than AD at 70 degrees C, while AD at 50 degrees C was the preferred method for drying leaves of E. purpurea.     

Flavor and texture of banana chips dried by combinations of hot air, vacuum, and microwave processing

The behavior of 16 volatile compounds of banana during a combination of air-drying (AD) and vacuum microwave-drying (VMD) of banana chips was characterized. Samples were AD to remove 60, 70, 80, or 90% of moisture (wet basis) and then subjected to VMD to achieve a final moisture content of 3% (dry basis). Banana slices were also dehydrated using only AD, VMD, and freeze-drying (FD) for comparison. Samples that underwent more VMD had significantly lower levels of volatile compounds, which is attributed to the decreased formation of an impermeable solute layer on the surface of the chips. High values for water solubility and relative volatility of compounds correlated with losses during VMD; however, additional factors appear to influence the behavior of compounds during VMD processing. The optimal process of 90%AD/10%VMD yielded crisper banana chips with significantly higher volatile levels and sensory ratings than AD chips.     

Effect of drying temperature on alkylamide and cichoric acid concentrations of Echinacea purpurea

Root and aerial sections (flower, stem, and leaf) of Echinacea purpurea were dried with hot air at temperatures in the range of 40-70 degrees C, and the concentrations of alkylamides and cichoric acid were determined after drying. Increasing drying temperature decreased from 48 h at 40 degrees C to 9 h at 70 degrees C but resulted in a decreased concentration of cichoric acid in all plant sections with a greater loss from aerial plant parts than from the root. There was, however, no significant difference in the concentration of the alkylamides at any drying temperature. Establishment of operational parameters for the drying of echinacea must therefore be structured around the more labile cichoric acid.     

From plums to prunes: influence of drying parameters on polyphenols and antioxidant activity

Prunes, which are industrially obtained by dehydrating fresh plums at 85-90 degrees C for 18 h, contain higher levels of phenolic compounds than most other fruits. Prune phenolics have shown beneficial effects on human health. Reports are available in the literature on ascorbic acid, phenol composition, and antioxidant activity of fresh plums and prunes, but there is a lack of publications on the influence of drying parameters on the phenolic compounds and antioxidant activity. A study was carried out on two plum cultivars using two sets of air-drying temperatures: (i) air temperature at 85 degrees C until 50% of prune moisture level and then the temperature was lowered to 70 degrees C; (ii) air temperature at 60 degrees C. Whole fresh and dried fruits were assessed for phenolics (catechins, hydroxycinnamic acids, anthocyanins, and flavonols), ascorbic acid, and antioxidant activity (all parameters were calculated on a dry matter basis). Analysis of data shows that chlorogenic and neochlorogenic acid changes were affected by both process parameters and cultivar. Drying destroyed anthocyanins, and there was a significant decrease in flavonols. Ascorbic acid was drastically reduced in relation to process temperature. The most striking result was that drying at 85 degrees C doubled antioxidant activity in both cultivars, while contradictory results were found for 60 degrees C processed plums.     

不同干燥方式对中国对虾风味组分的影响

为了研究不同干燥方式对中国对虾风味组分的影响,该文采用热风(温度:(50±2)℃,风速:1.5 m/s,时间:8 h)、冷风(温度:18~20℃,风速:1.5 m/s,时间:56 h)、微波真空(功率500 W,真空度70 kPa,时间:40 min)、微波真空-冷风联合(先温度为18~20℃,时间27h的冷风干燥,后功率500 W,真空度70 kPa,时间10 min的微波真空干燥)4种干燥方式对其干制品的游离氨基酸组成、呈味核苷酸、等鲜量以及挥发性成分进行研究。结果表明,热风干燥后的中国对虾总游离氨基酸质量分数为63.31 mg/g,相对于对照组鲜虾(72.04 mg/g)有明显损失(P0.05);呈味核苷酸质量分数为7.9 mg/g,较对照组(9.05 mg/g)损失严重(P0.05);其等鲜量(127 g/(100 g))较鲜虾(180 g/(100 g))显著降低(P0.05);对虾产生以烤肉香味和海鲜风味为主的挥发性成分。冷风干燥使中国对虾总游离氨基酸质量分数较对照组损失偏大,其值为63.70 mg/g(P0.05);等鲜量(155(g/100 g))损失较大(P0.05);挥发性成分以烃类化合物为主,风味较寡淡。微波真空干燥后的中国对虾呈味核苷酸和等鲜量分别为9.17 mg/g和176 g/(100 g),总游离氨基酸质量分数较对照组损失较严重,为55.81 mg/g(P0.05);挥发性成分以肉香味和烤香味为主。微波真空-冷风联合干燥后的中国对虾呈味核苷酸含量最高,其值是9.90 mg/g;等鲜量值为189 g/(100 g),相对于鲜虾有所提高(P0.05);总游离氨基酸质量分数为62.84 mg/g呈现降低(P0.05);产生以烤肉香味和海鲜风味为主的挥发性成分。因此,微波真空-冷风联合干燥方式对中国对虾风味变化影响最小,是一种具有发展前景的干燥方式。     

Effect of harvesting and drying conditions on chlorophyll levels of soybean (Glycine max L. Merr)

Chlorophyll in soybean represents a downgrading factor for the crops. Five Brazilian cultivars were harvested between R(6) and R(8) stage of development (Fehr & Caviness scale) and dried at 25 degrees and 40 degrees C. The effect of maturity stages and two drying conditions after harvest were studied to achieve reduction of moisture and chlorophylls to acceptable levels. When seeds were dried at 25 degrees C, even harvesting at early stages of development such as R(6), the green pigments were almost degraded, and 16 ppm of chlorophyll were found at maximum, accompanied by loss of moisture. Moisture and chlorophyll declines as seed matures, but at intermediary stages (R(6)-R(7)), chlorophyll degrades first, so the rate of moisture loss should not be used to predict chlorophyll contents. At 40 degrees C, complete degradation of chlorophyll pigments is only achieved when seeds are swathed from R(7) stage up, otherwise the seed quality could be compromised. Slow drying allows almost complete removal of green pigments, even when seeds are swathed a few days before the physiological maturity stage.     

三种干燥技术对红枣脆片干燥特性和品质的影响

为了解决传统油炸红枣脆片含油率高、维生素C损失严重及褐变等问题,探索红枣脆片新的加工方法,该文以新鲜脆熟期红枣为原料,利用气体射流冲击、中短波红外、真空脉动3种干燥技术进行非油炸红枣脆片的生产加工,对比了3种干燥方式对红枣脆片的干燥特性、色泽、维生素C保留率、复水性能、质地以及微观结构的影响。结果表明：1）红枣脆片在3种干燥方式下均表现为降速干燥,其中气体射流冲击干燥时间最短,为105 min,气体射流冲击、中短波红外、真空脉动干燥方式的水分有效扩散系数分别为1.55×10-9、1.03×10-9、0.89×10-9 m2/s;2）干燥方式对枣片色泽具有显著性影响（P<0.05）,真空脉动干燥所得枣片与新鲜枣片色泽最为接近;3）气体射流冲击、中短波红外、真空脉动干燥方式干燥后红枣脆片的维生素C保留率分别为51.5%、49.0%、66.6%,真空脉动干燥所得枣片维生素C含量保存率明显高于其他两种干燥方式（P<0.05）;4）气体射流冲击、中短波红外、真空脉动干燥方式加工的红枣脆片脆度分别为8.64、8.77、11.38 N,真空脉动干燥方式所得枣片最为酥脆;5）扫描电镜观测表明3种干燥方式均能得到疏松多孔的组织结构,真空脉动干燥所得枣片比气体射流和中短波红外干燥所得枣片组织结构更为疏松。从干燥时间来看气体射流冲击干燥耗时最短,但3种干燥方式所得红枣脆片色泽、维生素C保留率、复水性能和质地均以真空脉动干燥最优。该研究为低含油率和高品质红枣脆片的加工工艺选择提供了一定的理论依据。     

苦杏仁去皮热风干燥适宜温度提高油脂品质

为探索适宜的杏仁热风干燥温度,以热烫去皮处理后的湿杏仁为试验材料,研究了热风干燥不同温度对杏仁及其油脂的感官、理化和营养品质的影响。结果表明,经热烫去皮、干燥处理后可以得到颜色较浅的杏仁油,有利于提高杏仁油的感官品质,但会造成杏仁油过氧化值显著升高(P0.05),油酸、亚油酸、十七碳烯酸、二十碳一烯酸等不饱和脂肪酸的比例和甾醇含量降低,棕榈酸、棕榈油酸、硬脂酸、十七碳烷酸、二十碳烷酸、二十碳一烯酸的比例和总生育酚含量升高,对杏仁油的理化特性和营养品质产生影响。但不同脂肪酸及其伴随物种类、不同温度处理变化幅度不同。随着干燥温度的提高,干燥速率逐渐加快,杏仁及杏仁油的颜色逐渐加深,杏仁油亮度下降,酸价略有升高,但不同干燥温度之间差异不显著(P0.05);过氧化值呈上升趋势,且80℃以上干燥处理显著高于40℃和60℃干燥处理(P0.05);总不饱和脂肪酸、油酸、亚油酸、十七碳烯酸、二十碳烷酸的比例及β-生育酚、δ-生育酚及总生育酚含量总体呈下降趋势,棕榈油酸、棕榈酸、硬脂酸的比例和β-谷甾醇、总甾醇含量总体呈升高趋势。低温干燥有利于提高杏仁油中生育酚含量,而提高干燥温度则有利于杏仁油中植物甾醇含量的提高。尤其是干燥温度为80℃以上时,杏仁油的品质变化加快。因此,为提高杏仁油理化与营养品质,杏仁脱皮后的干燥宜在80℃以下的较低温度条件下进行。研究结果可为杏仁干燥和高品质杏仁油加工提供参考。     

双孢菇片微波真空干燥特性及工艺优化

为解决双孢菇的干制问题,采用微波真空干燥技术对双孢菇片进行干燥试验,研究双孢菇片的干燥特性,并与热风干燥、真空干燥和冷冻干燥方法进行比较。研究结果显示,微波真空干燥时,微波强度对双孢菇片的干燥速率有显著影响,而真空度影响较小,最优的干燥参数为：微波强度为17.4 W/g,真空度70 kPa,干燥时间20 min,含水率可达6.9%。通过对比4种干燥方法的干制时间及产品的复水率、色泽和维生素C含量,可知微波真空干燥的菇片品质接近冷冻干燥,明显优于热风干燥和真空干燥,而微波真空干燥在干制时间方面要比冷冻干燥明显缩短。微波真空干燥是适合双孢菇片的有潜力的干制技术。     

蕨菜微波真空干燥特性和品质试验研究

为了快速干燥蕨菜这种营养价值高但难于鲜藏的特色山野菜,利用微波真空干燥技术,对蕨菜进行正交干燥试验,研究蕨菜干燥特性;并与冷冻干燥、热风干燥方法相比较,分析不同干燥方法对蕨菜干品品质的影响.在蕨菜的微波真空干燥过程中,微波功率对干燥速度的影响要高于真空度,并且提出了蕨菜含水率与微波功率、干燥时间和真空度之间的回归模型;对3种方法干燥后的蕨菜在颜色、维生素C含量和复水性方面进行对比,结果表明:微波真空干燥的蕨菜的复水性优于热风干燥和冷冻干燥;微波真空干燥后的蕨菜品质与冷冻干燥几乎相同,明显高于传统的热风干燥品质.微波真空干燥技术是适合蕨菜脱水的有潜力的干燥技术.     

Role of the waxy skin layer in moisture loss during dehydration of prunes

Permeability studies of water through the skin and flesh of d'Agen plums have been carried out by radiotracer and PGSE NMR techniques as a function of moisture content. The results have shown that the diffusion coefficient of water through the skin layer increases as the fruit is dried at 70 degrees C or above. By contrast, the water diffusion through the fruit becomes more hindered as moisture is lost and structural collapse of the cell layers takes place. Values for diffusion coefficients of water at 21 degrees C through the fruit of 1 x 10(-)(9) m(2) s(-)(1) for fresh plums and 2.0 x 10(-)(10) m(2) s(-)(1) for fruit dried to 50% moisture content (wet basis) were found. Structural studies using scanning electron microscopy techniques were also performed. These showed that drying induces marked changes to the waxy skin layer of the fruit as well as the fruit flesh. These results are discussed in terms of the important role that the plum skin has in modulating the moisture loss process during dehydration, particularly at early stages of drying.     

Drying temperature and relative humidity effects on wheat gluten film properties

The mechanical and physical properties of glycerol-plasticized wheat gluten films dried at different temperatures (20, 50, and 80 degrees C) and relative humidities (35 and 70% RH) were investigated. Dispersion of wheat gluten was prepared at pH 11 in aqueous solution. Films were obtained by casting the wheat gluten suspension, followed by solvent evaporation in a temperature and relative humidity controlled chamber. Decreasing relative humidity altered most of the mechanical properties. At 35% RH, tensile strength increased when drying temperature increased. However, at 70% RH, tensile strength decreased when temperature increased. Thickness of the films decreased by increasing temperature. Hypothetical coating strength increased with increasing drying temperature at 35% RH. However, at 70% RH, a maximum value was observed at 50 degrees C. Films produced at 80 degrees C exhibited low solubility in aqueous solution. Addition of 1.5% (w/v) sodium dodecyl sulfate increased solubility of all of the films except the film dried at 50 degrees C and 70% RH. Overall, drying temperature and relative humidity affected mechanical and physical properties of the wheat gluten films. However, the effect of drying temperature was more pronounced than the effect of relative humidity.     

Stability of dried and intermediate moisture tomato pulp during storage

Commercial tomato pulp was air-dried to two final moisture contents in order to obtain intermediate moisture pulp (IMP, 23% moisture) and dried pulp (DP, 9% moisture). IMP and DP were stored at 4, 20, and 37 degrees C for approximately 5 months; periodically samples were analyzed to evaluate heat and oxidative damage by measurement of color changes, total phenolics, rutin, lycopene and furosine concentrations, and antioxidant activity of the lipophilic extract. IMP and DP, despite different drying degree, had similar antioxidant activity; in fact, whereas lycopene was stable to drying treatments, ascorbic acid was totally degraded in both products. During storage, IMP and DP showed different behavior: IMP was more sensitive to degradation than DP, especially with regard to lycopene, rutin, and antioxidant activity degradation and to nonenzymatic browning. Effects of storage temperature varied with regard to different parameters: variations in rutin, furosine, and color indices were higher in products stored at higher temperatures, while lycopene and antioxidant activity of the lipophilic fraction were maximally degraded in products stored at 4 degrees C.     

Structural changes in apple rings during convection air-drying with controlled temperature and humidity

The structure of heat pump dried apple slices, developed as a function of air temperature and constant humidity, was studied by measuring porosity and using electron microscopy. The porosity of the apple rings increased linearly when the moisture content decreased during drying and then reached a constant value. In all dried apple slices, a degree of cellular collapse occurred. Case hardening occurred in the surface of the dried tissue when the apple slices were dried at 40-45 and 60-65 degrees C, and in the extreme case (at 60-65 degrees C) cracks were formed on the surface.     

Physicochemical Properties of Rice Dried in a Single Pass Using High Temperatures

This study evaluated the physicochemical properties of high‐temperature, single‐pass dried rough rice. Pureline cultivars Wells (long grain) and Jupiter (medium grain) and hybrid cultivar CL XL729 (long grain), at initial moisture contents of 17.9–18.1% were dried in a single pass to approximately 12.5% moisture content with drying air temperatures of 60, 70, and 80°C and relative humidities of 13–83%. Immediately after drying, the samples were tempered for 1 h at the drying air temperatures in sealed plastic bags. Color, degree of milling, pasting viscosity, and thermal properties of the milled rice were evaluated. Results showed that color, degree of milling, and thermal properties were not affected by drying treatments. However, peak and final viscosities increased with increasing drying air temperatures in all three cultivars.     

玫瑰花的微波真空干燥试验

为了提高玫瑰干花品质,减少干燥时间。该研究通过试验性微波真空干燥设备对玫瑰花进行干燥,比较了不同真空度和微波功率对玫瑰干花品质的影响。研究结果表明,真空度越高,物料内水分蒸腾而干燥的速度越快,物料温升越低。随着微波功率增加,干燥时间大大缩短。综合考虑玫瑰干花干燥时间、温度、形态变化和颜色等指标,并与热风干燥相比,选择真空度0.10 MPa,微波功率200 W,干燥时间80 min的微波真空干燥工艺为较适宜的干燥条件,研究结果为玫瑰花的干燥和工业化生产提供一定的理论依据。     

Effect of different washing procedures on phenolic metabolism of shredded, packaged iceberg lettuce during storage

Different washing treatments applying chlorinated, ozonated, and tap water were examined for their effect on the phenolic metabolism of minimally processed iceberg lettuce (Lactuca sativa L.) during storage in consumer-sized bags at 4 degrees C for up to 9 days. To eliminate problems associated with raw material inhomogeneity, processing was conducted on a pilot-plant scale under operating conditions of industrial practice. Inherent product heterogeneity caused by diverse lettuce leaf tissues was compensated for by pooling large-sized samples, and frequent sampling ensured significant data about the activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD), as well as the contents of caffeic acid derivatives over storage time. In the homogeneous lettuce samples, specific responses caused by different washing procedures were detectable. PAL activity in the samples increased for up to 5-8 days of storage. Compared to tap and ozonated water, the use of chlorinated water (100-200 mg/L free chlorine) for washing trimmed heads or shredded lettuce significantly reduced PAL activity and the concomitant rise of 3,5-di-O-caffeoylquinic acid (isochlorogenic acid isomer) concentrations. The phenolic acids O-caffeoyltartaric (caftaric acid), di-O-caffeoyltartaric (chicoric acid), 5-O-caffeoylquinic (chlorogenic acid isomer), and O-caffeoylmalic were less influenced by different washing treatments. Individual contents either were constant or decreased during storage. Additionally, the novel finding of a further caffeic acid isomer, tentatively identified as meso-di-O-caffeoyltartaric acid, is reported. PPO and POD activities were less affected by different washing treatments and thus were less suitable physiological indicators of stress reactions triggered by alternative processing.     

Impact of drying method on broiler litter analyses

Abstract

Drying broiler litter prior to chemical analyses may alter its chemical composition and result in excessive or inadequate nutrient applications to crops if such analyses are used for recommendation purposes. A study was conducted to determine the effect of drying method and temperature on broiler litter N, P, K, Cu, Fe, and Zn contents. Treatments consisted of no drying (ND), air drying (AD), oven drying at 40°C (OD40), oven drying at 60°C (OD60), microwave drying at 40°C (MW40), microwave drying at 60°C (MW60), and freeze drying at ‐40°C (FD). All drying treatments lost N when compared to ND, and greatest losses were observed with the FD, OD60 and AD treatments; losses were 15, 12 and 12% of the ND total N, respectively. Changes in broiler litter P, K, Cu, Fe and Zn due to drying were small and were inconsequential with respect to agronomic and environmental considerations. It appeared that maintaining broiler litter in a moist, refrigerated state before chemical analyses was more desirable than drying. However, our results show that from a practical standpoint, the MW40 treatment may be a desirable alternative.     

微波真空干燥扇贝柱的物理和感观特性研究

微波真空干燥是一项新兴食品干燥技术。进行了扇贝柱的微波真空干燥试验，研究了微波真空干燥参数对扇贝柱物理和感观特性的影响规律，并与传统的自然干燥和热风干燥进行了对比分析。结果表明，不同微波功率和真空度组合对扇贝柱的物理和感观特性有明显影响，在微波功率和真空度为3 W/g和0.090 MPa时，干燥扇贝柱具有良好的色泽及表面质量，仅需30 min即可达到20%湿基含水率，收缩率和复水率与自然干燥扇贝柱相近；减小微波功率和降低真空度至2 W/g和0.074 MPa时，干燥扇贝柱的收缩率会增加、色泽和表面质量会变差。试验结果还表明，各种参数组合条件下的微波真空干燥扇贝柱，其干燥速度和抗破碎能力均明显优于自然干燥及热风干燥。利用微波真空干燥扇贝柱，对提高干燥速度和改善产品品质具有明显优势。     

山核桃坚果分段变功率微波干燥工艺参数优化

为了提高山核桃干果品质、缩短干燥时间和降低干燥能耗,以前期微波功率密度、转换点含水率和后期微波功率密度为试验因素,对山核桃坚果分段变功率微波干燥工艺进行了试验研究。通过单因素试验,研究了山核桃坚果微波干燥特性,确定了山核桃坚果微波干燥各因素合适范围。通过三因素五水平的二次回归正交试验,建立了三因素与失水速率、单位质量干燥能耗以及干燥后物料蛋白质保存率、不饱和脂肪酸保存率、感官品质指标综合分值的二次回归数学模型,分析了三因素对各指标影响的显著性。利用多目标非线性优化方法,确定了山核桃坚果分段变功率微波干燥的最佳工艺参数组合,即前期干燥微波功率密度为6.5 k W/kg,转换点含水率为23.4%(干基),后期干燥微波功率密度为3.3 k W/kg。在此条件下,山核桃坚果失水速率为4.072%/min、单位质量干燥能耗为3.467 k W·h/kg、蛋白质保存率为92.15%、不饱和脂肪酸保存率为91.63%、感官品质指标综合分值为35.28分。研究结果为山核桃坚果干燥加工生产提供一定的理论依据。