Effect of hot air drying and sun drying on color values and β-carotene content of apricot (Prunus armenica L.)

In this study, sulphurated and nonsulphurated Hacihaliloglu apricots (Prunus armenica L.) which is the most widely produced cultivar in Turkey were used to study the effects of different hot air drying temperatures (50, 60, 70, and 80 °C) and sun drying on color and β-carotene content of apricot. The time required to obtain the desired final dry matter in hot air drying was lower than sun drying. Sulphuration also decreased drying time at all drying conditions. Color values and β-carotene content of hot air dried samples were favorable in comparison to air drying. β-carotene content in dried apricots at 70 and 80 °C was 7.14, 7.17 mg 100 g⁻¹ dry matter and 6.12, 6.48 mg 100 g⁻¹ dry matter for sulphurated and nonsulphurated apricots, respectively. A good relationship was found between treatments (drying temperatures and drying times) and β-carotene content for sulphurated and nonsulphurated apricots (R²=0.9422 and 0.9129, respectively).     

微波干燥条件对杏脯干燥特性与品质的影响

目的:提高杏脯的干燥效率及产品品质。方法:分别用转盘式微波炉(RMD)和微波对流耦合干燥机(MCD)干燥杏脯,考察微波功率、微波发射方式、切分程度及物料是否转动对杏脯干燥特性、焦化率、色值、感官品质及复水特性的影响,并与传统热风干燥(HD)进行比较。结果:与HD的1 040 min(16块)和840 min(48块)相比,微波干燥显著缩短干燥时间,不同微波干燥条件下所需的干燥时间为40～400 min;脉冲比越大或功率越高或物料尺寸越大,干燥所用时间越短,在MCD中控温微波干燥耗时最长。无论是在RMD还是不控温MCD中静态干燥,杏脯均出现严重的烧焦现象,焦化率为17%～100%,物料转动时焦化率高于静态干燥的,而在MCD中控温静态干燥避免了物料的烧焦现象,且MCD中控温静态干燥的杏脯色值和感官评价最接近HD的,复水比与HD仅相差3.45%～5.17%,获得最高的感官评价分(87.2分)。结论:MCD中控温静态干燥可以作为杏脯的高效干燥方法。     

MATHEMATICAL MODELLING of MOISTURE, VOLUME and TEMPERATURE CHANGES DURING DRYING of PRETREATED APRICOTS

Simultaneous heat and mass transport in dehydration of apricots is presented. the moisture variation of apricots, pretreated with various combinations of sodium-meta-bisulphite and ethyl oleate solutions, was analyzed by Exponential and Page equations. Use of ethyl oleate in addition to sodium-meta—bisulphite as a pretreatment solution was observed to decrease drying times of apricots. the system of differential equations determining the unsteady-state temperature distribution was solved. Thermophysical properties were taken to be moisture dependent. the variation of volume upon drying (shrinkage) was introduced into the solution by taking space intervals to be variable in the apricot side while they were taken to be constants in the stone side. the dominant mass transfer mechanism was diffusion while diffusivity of water changed depending upon the pretreatment solution. Comparison between predicted and experimental data shows good agreement for both moisture and temperature variation of the apricots throughout the drying process.     

硫处理对杏干品质及贮藏过程中SO_2残留量的影响

以鲜杏为原料经预处理后进行自然晒干,研究杏成熟度、亚硫酸氢钠添加量、处理时间等对杏干感官品质的影响;将杏干采用PA/CPP材料密封包装,分析了贮藏过程中二氧化硫残留量的变化趋势。研究结果表明,高浓度、长时间处理会导致果皮与果肉分离、果肉质地疏松、软烂、汁液外流等现象,处理过度的鲜杏晒干后杏干外观收缩严重、变形、果肉组织不饱满,已不再适宜进行二次加工;随着鲜杏中亚硫酸氢钠使用量的增大及鲜杏成熟度的增加,杏干中二氧化硫的残留量逐渐增加;随着贮藏时间的延长残留量逐渐减少,不同成熟度、各处理下降趋势相同。以青杏为原料的杏干在亚硫酸氢钠处理量为2、2.5、3、3.5、4g/kg的条件下,二氧化硫日损失率分别为0.38%、0.3%、0.3%、0.17%、0.17%;以黄杏为原料的杏干在亚硫酸氢钠处理量为2、2.5、3、3.5、4g/kg的条件下,二氧化硫日损失率分别为0.39%、0.32%、0.29%、0.24%、0.16%。     

Low humidity air drying of apple slices: Effect of EMR pretreatment on mass transfer parameters,energy efficiency and quality

The apple slices were treated with electromagnetic radiations (EMR) namely, infrared (IR) and microwave (MW) and dried using low humidity air (LHA) and normal hot air (HA) at 40 °C. The effect of EMR pretreatment on drying kinetics, mass transfer, shrinkage, porosity, energy efficiency and product quality was evaluated. The combination of EMR pretreatment with LHA drying reduced the drying time by 23.4 to 27.3%, and the dried product had lower shrinkage (60 to 65%) as well as higher porosity (0.38 to 0.45) compared to control. Among the EMR pretreatments, IR treated slices retained a higher amount of ascorbic acid (78.68%), phenolic content (74.42%), antioxidant activity (79.54%) and better color compared to MW treated. EMR pretreatment reduced the energy requirement for drying by 26.5 to 37.1%. The mass transfer parameters (moisture diffusivity and mass transfer coefficient) estimated using the analytical model proposed by Dincer and Dost showed higher values for EMR treated samples. Moisture content predicted for both the drying methods showed good agreement with experimental values. The present study demonstrated that for heat sensitive products like apple, a combination of IR pretreatment and LHA drying could be effective for reducing drying time as well as energy requirements and also to obtain better quality products.     

樱桃番茄渗透预处理热风干燥特性研究

为了提高干制品的营养保留率和品质,进行了渗透预处理联合热风干燥的工艺路线的实验研究。以樱桃番茄为例,分别对不同浓度(50%,70%)蔗糖溶液常压渗透以及真空渗透处理后热风干燥的干燥时间、干燥速率、样品体积比、Vc保留率、硬度、颜色等参数分别进行测定和比较。结果表明:渗透预处理可以除去新鲜樱桃番茄中的大部分自由水,从而减少其热风干燥时间,使产品在高温中的暴露时间减少,从而缩短整体干制时间、提高干制效率及营养品质。经渗透预处理的樱桃番茄干制产品的体积比和Vc保留率要比直接热风干燥的产品增加,而硬度大大下降;其中经浓度为50蔗糖溶液真空渗透预处理后干燥产品的体积比、Vc保留率以及硬度是直接70℃热风干燥的1.72、2.26和0.12倍;而且产品的色泽更加接近新鲜原料,使产品的口感和感官品质更好。研究表明,渗透预处理联合热风干燥是1种很有发展前景的制干工艺。     

串联式5HT-2农副产品太阳能干燥装置性能研究

对单体5HT-2型农副产品太阳能干燥装置(简称SD装置)进行串联改造,每套装置占地5.3m2,场地利用率较单体提高29%。在杏干燥期间,串联SD装置的集热器出口温度平均为50℃,分别较单体和环境高出6,15℃。正午时较环境温度高20℃以上的温升保证率可达65%以上。串联SD装置的干燥室温度平均为36℃,分别较单体和环境高出2,5℃,正午时3℃以上的温升保证率可达99%以上。采用串联SD装置进行杏子的制干,水分含量日平均散失高于单体5%左右,说明串联SD装置有效提高了热空气的利用效率,不仅可缩短杏子的干燥时间,而且杏干品质与单体SD装置所生产的杏干品质相当,均显著优于传统摊晒杏干。     

Effects of microwave and hot‐air drying methods on colour, β‐carotene and radical scavenging activity of apricots

The effects of drying by microwave and convective heating at 60 and 70 °C on colour change, degradation of β‐carotene and the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) scavenging activity of apricots were evaluated. Microwave heating reduced significantly the drying time (up to 25%), if compared with convective one, also owing to the higher temperature reached during the last phase of the process, as monitored by infrared thermography. Colour changes of apricot surface, described with lightness and hue angle, in both drying methods followed a first‐order reaction (0.927 ≤ R² ≤ 0.996). The apricots dried by microwave were less affected by the darkening phenomena. The evolution of β‐carotene in fresh apricots (61.2 ± 5.6 mg kg^?1 d.w.) during the drying highlighted a wider decrease (about 50%) when microwave heating was employed for both the temperatures used. Radical scavenging activity increased (P < 0.05) in all dried samples except for hot‐air dried apricots at 60 °C.     

不同工艺条件对低硫杏脯二氧化硫残留量的影响

目的研究不同工艺参数对低硫杏脯二氧化硫残留量的影响,探索最优控制工艺条件使低硫杏脯制品食用更安全。方法采用单因素实验和正交实验,分析真空度、真空预抽时间、焦亚硫酸钠溶液浓度和真空渗糖时间对低硫杏脯二氧化硫残留量的影响。结果在真空度0.08 Mpa、真空预抽时间1 h、焦亚硫酸钠溶液浓度0.2%、真空渗糖时间2 h条件下,二氧化硫残留量最低,仅为0.0130 g/kg。结论采用此工艺条件制成的杏脯,食用安全性较高,可以满足消费者对绿色食品消费的需求。     

Improving the Sun Drying of Apricots (Prunus armeniaca) with Photo‐Selective Dryer Cabinet Materials

Photo‐selective materials have been studied for their effects on the preharvest quality of horticultural crops, but little work has been done on potential postharvest processing effects. The aim of this work was to characterize the effects of 5 different photo‐selective acrylic materials (used as the lid to a single‐layer sun drying cabinet) on the drying rate and quality of apricots (Prunus armeniaca). Photo‐selective cabinet materials that transmit light in the visible portion of the solar spectrum accelerate the apricots’ drying rate in both the early period of drying and the course of drying as a whole. These materials do not significantly affect the measured quality metrics during the first day of sun drying. However, when drying is taken to completion, some minor but significant quality differences are observed. Infrared‐blocking material produces dried apricot with lower red color, compared to clear, opaque black, and ultraviolet‐blocking materials. Clear material produced dried apricot with significantly lower antioxidant activity, compared to black and infrared‐blocking materials. Using appropriate photo‐selective drying cabinet materials can reduce the required sun drying time for apricots by 1 to 2 d, compared with fully shaded drying. Ultraviolet‐blocking material is recommended to maximize drying rate and minimize quality degradation.     

一氧化氮熏蒸工艺对鲜杏制干品质的影响

针对硫化方法易导致杏干果实发生漂白、异味及二氧化硫(sulfur dioxide,SO2)残留量高等问题,本研究以新疆吊干杏为材料,利用NO对杏果实进行制干前、后熏蒸工艺处理;研究在常温((25±1)℃)贮藏条件下,杏干生理指标、NO残留情况及感官品质的变化.结果表明,NO熏蒸能较好维持杏干的水分质量分数和水分活度(w...     

微波真空冷冻干燥对芒果干制品品质特性的影响

为获得较优的芒果干燥方法,以复水性、感官为评价指标,比较微波真空冷冻干燥、热板真空冷冻干燥和热风干燥3种不同干燥方法对芒果干制品品质的影响。结果表明：真空冷冻干燥法的产品各项指标均优于热风干燥法。微波真空冷冻干燥的产品复水性最好,25℃与100℃最大复水比分别为3.363、3.674;其次为热板真空冷冻干燥,两温度条件下与微波真空冷冻干燥产品复水比相差较小;热风干燥产品复水性最差,分别为2.140、3.028。感官指标中色泽、香气和口味3方面均为：微波真空冷冻干燥＞热板真空冷冻干燥＞热风干燥。     

超声辅助热风干燥柠檬片的动力学研究及其维生素C含量的变化

采用超声波预处理柠檬片,以干基含水量、干燥速率、复水率、维生素C含量为主要指标,研究超声处理时间对柠檬片干制的影响。结果表明:超声波预处理后热风干燥柠檬片的干燥速率增加,干燥所需时间至少缩短20%,热风干燥阶段耗能量明显降低;试验范围内的探针式超声处理时间越短,干燥速率越大,而一定范围内的水浴式超声预处理时间越长,干燥速率越大。超声波预处理不仅能降低柠檬片热风干燥时维生素C的损失,而且对干制品的复水率也有较好的改善效果。探针式超声波预处理时间越长,维生素C损失越大,复水比降低,应用中需选择较短时间的预处理;随着水浴式超声波预处理时间的延长,干制柠檬片中维生素C含量呈平缓下降的趋势,复水比逐渐增大,而超声预处理时间延长至11 min后,变化不明显(P<0.05)。探针式超声波预处理3 min、热风干燥160 min的柠檬片中维生素C的含量为32.93 mg/100 g,复水比4.61±0.08;水浴式超声波预处理11 min、热风干燥160 min的柠檬片中维生素C的含量为29.70 mg/100 g,复水比4.60±0.13。     

Effect of temperature on the drying characteristics,colour, antioxidant and beta‐carotene contents of two apricot varieties

In this study, the drying characteristics, colour, oxygen reactive antioxidant capacity (ORAC) and beta‐carotene contents of two apricot varieties dried at different temperatures were compared. The hot air drying of apricot slices for both varieties consisted of a constant rate period (CRP) and two of falling rate periods (FRP). The CRP drying rate and the first and second FRP drying coefficients increased with drying temperature for both apricot varieties. The first and second FRP of both apricot varieties gave activation energies of 23.5–28.7 and 25.6–29.3 kJ mole^?1, respectively. The colour values (L*, a* and b*) of both dried apricot varieties decreased with increasing temperature, while the total colour change of both dried apricot varieties increased with temperature. The chroma, hue angle and browning index values of both dried apricot varieties decreased with increasing temperature, and the hydrophilic ORAC and beta‐carotene contents increased with drying temperature.     

干燥方法对脱水柑橘皮品质特性的影响

研究了冷冻干燥、变温压差膨化干燥、热风干燥3种干燥方法对脱水柑橘皮品质特性的影响.试验结果表明:冷冻干燥柑橘皮色泽好,复水率高.采用变温压差膨化干燥方法制备的脱水柑橘皮色泽、质构酥脆性、复水能力均强于热风干燥法,其表观密度也低于热风干燥产品.选择不同的干燥方法对脱水柑橘皮品质特性影响显著.     

微波辅助热风干燥预处理对油炸紫薯片品质的影响

为研究微波辅助热风干燥预处理对油炸紫薯片品质的影响,以厚度为3 mm的新鲜紫薯片为对象,首先采用不同微波功率(259、280、358 W)辅助热风(50、60、70 ℃)干燥方式对紫薯片进行预干燥,对不同微波功率(259、280、358 W)干燥后的紫薯片油炸8、3.5、2.5 min,研究紫薯片预处理过程的干燥特性及花青素含量,以及油炸紫薯片产品的色泽、脆度、硬度和脂肪含量等。结果表明:随着微波预处理功率的升高,紫薯片达到干燥终点的时间缩短(90 min以上),平均干燥速率显著提高;并且热风干燥温度越高,微波预处理对干燥效率的促进作用也越明显。而低功率(259 W)的微波辅助50 ℃热风干燥联用更有利于干燥紫薯片花青素的留存;较低功率(259、289 W)的微波预处理不仅在保护产品颜色上具有优势,还可以使得油炸紫薯片更高的硬度和更好的脆性。在不同微波预处理功率下,油炸紫薯片的脂肪含量最低值基本一致。本研究可为微波辅助热风技术在干燥紫薯及其他农产品干燥中的应用提供参考。     

莴苣微波喷动均匀干燥工艺

通过单因素实验和正交实验确定莴苣微波喷动干燥的最佳工艺参数,并将产品和热风、喷动、真空冷冻、真空微波干燥的产品进行比较,旨在发现微波喷动干燥的优势所在。产品的质量主要通过复水率、叶绿素质量分数、色泽、能耗、感官评定等方面来衡量。实验结果表明,莴苣最佳微波喷动干燥参数为干燥前期(10min),微波功率为300W,热风温度为68～78℃,喷动风速为8m/s;干燥后期(45min)微波功率为200W,热风温度为68～78℃,喷动风速为6m/s。检测结果表明,微波喷动干燥产品的复水性、叶绿素质量分数、色差值和感官评定均优于热风干燥、喷动干燥和真空微波干燥产品,复水性和叶绿素质量分数略低于真空冷冻干燥产品,微波喷动干燥在节约能耗方面有显著效果。     

大球盖菇粉的热风干燥工艺研究

以大球盖菇为原料,对热风干燥制作大球盖菇粉的加工工艺和护色剂的护色效果进行研究。结果表明,热风干燥前,对大球盖菇进行护色处理可提高干制菇片的色泽,复合护色液的最佳配方为亚硫酸钠0.1%、50℃、柠檬酸0.3%。干燥温度、蘑菇切片厚度和装载量对大球盖菇粉的色泽有显著影响,其中干燥温度对色度影响最为显著。大球盖菇粉制备的最佳工艺条件为:干燥温度50℃、切片厚度4 mm、装载量2 kg/m^2、干燥时间8 h,按此工艺生产的大球盖菇粉的色泽接近冷冻干燥粉,且具有较好的功能特性。     

预处理方式对热风干燥玫瑰花瓣品质特性的影响

采用5%柠檬酸溶液、20%糖溶液、20%NaCl和柠檬酸混合溶液浸渍、烫漂4种处理方式处理玫瑰花瓣,以未预处理的花瓣作为对照,进行热风干燥对比试验和分析,对花瓣品质特性(色泽、总黄酮含量、总酚含量)以及微观结构等进行比较,并结合模糊数学综合评判法进行感官评定。结果表明:预处理方式对玫瑰花瓣的干燥速率有显著影响,且在含水率较高时尤其明显;微观结构有一定的差异性。其中,5%柠檬酸溶液组耗时最长,ΔE最小;20%糖溶液组复水比最低;混合溶液组色泽变化ΔE最大,总酚含量最高;烫漂组耗时最短,总黄酮含量和复水比最高。经烫漂预处理后的花瓣干燥后得到的感官评分值最高,对应的干燥时间、ΔE、复水比、总黄酮含量及总酚含量分别为120min、18.17±0.54、3.01、0.27mg/g、1.43mg/g。因此,采用烫漂预作为预处理方式可以提高食用玫瑰花瓣干制品的品质。     

超声处理对中短波红外干燥红枣时间及品质的影响

为提高红枣干燥品质,减少干燥时间,以干燥时间为响应值,响应面优化得到红枣中短波红外干燥前超声处理条件为：频率40 kHz、时间40 min、功率350 W。最优超声处理后中短波红外干燥红枣至其干基含水率约为40%时所需干燥时间为9.55 h;未超声处理中短波红外干燥需13.33 h;传统热风干燥需17.13 h。扫描电镜观察红枣果皮,超声处理40 min使果皮表面产生大量裂缝,表皮层变薄,仅38.8 μm,表皮层和亚表皮层易分离,利于干燥过程中水分扩散,显著缩短中短波红外干燥时间。红枣超声处理后中短波红外干燥的干制品品质显著优于未超声处理红外干燥,极显著优于传统热风干燥。最优超声处理条件结合中短波红外干燥,所得干制品在3 种处理方式中总VC、总酚、总黄酮含量最高,糖酸比最高,色泽最优,能耗最少,是适合红枣干燥的技术方法。