热泵温度对白萝卜干燥速率及品质的影响

分别以热泵温度50,55,60,65℃对白萝卜进行干燥,比较不同热泵温度下的白萝卜干燥速率、色泽、营养成分、复水率、微观组织结构等。结果表明:热泵温度50,55,60,65℃下,白萝卜含水量降至(8±1)%分别需12,11,10,9h;热泵温度55,60℃对白萝卜色泽保持较好;影响白萝卜干复水率的热泵温度依次为55℃>60℃>50℃>65℃,其中55,60℃下差异不显著(P>0.05);白萝卜干总糖、蛋白质和VC含量以热泵温度50℃干燥的较高,且随热泵温度的升高而降低;而热泵温度过低或过高都会对产品品质产生不利影响。综合考虑,热泵温度55℃可作为白萝卜热泵干燥的最佳干燥温度,此条件下获得的白萝卜干具有最佳的综合品质。     

Effects of Low Temperature Cooking on the Retention of 4-(Methylthio)-3-Butenyl Isothiocyanate (MTBITC) of Chinese White Radish (<Emphasis Type="Italic">Raphanussativus</Emphasis> L.)

This paper studied the effects of different cooking conditions (methods, temperatures and time) on the retention rate of 4-(methylthio)-3-butenyl isothiocyanate (MTBITC) in Chinese white radish by using a method of ultrasound extraction coupled with gas chromatography—flame ionization detector (GC-FID). Results showed that the retention rate of MTBITC decreased with increasing cooking time and temperatures. The retention rate of MTBITC declined dramatically after holding for 1 min at 85 or 95 °C. The fitted equations demonstrated that the degradation of MTBITC followed an exponential decay pattern for non-microwave (water bath or steam stove) cooking, while for microwave cooking, the degradation of MTBITC followed approximately a linear decay.     

LF-NMR动态分析4种干燥方式下鱿鱼干的复水特性

以鱿鱼为研究对象,采用自然晒干、热风干燥、热泵干燥、真空冷冻干燥4种干燥技术干制鱿鱼,结合鱿鱼干的肌纤维微观结构和复水率,通过低场核磁共振(LF-NMR)动态分析鱿鱼干复水过程的水分迁移和分布,探讨干燥方式对鱿鱼干复水的影响。结果表明,4种干燥方式中,真空冷冻干燥的鱿鱼干水分含量最低,氧化程度也最低(比其它3种处理的低1.5~6.7倍)。电镜扫描图显示鱿鱼干肌纤维内部有大量疏松多孔的蜂窝状结构,且真空冷冻干燥复水最快。复水过程,部分结合水向不易流动水迁移,不易流动水含量明显增加,且占比90%以上,自由水含量也有所提升。LF-NMR分析也表明真空冷冻干燥的鱿鱼干复水效果最好,复水后可截留更多的自由水。热泵干燥的鱿鱼干复水效果与自然干燥接近,热风干燥的复水率最差。干燥方式对干制品复水效果影响明显,真空冷冻干燥和热泵干燥技术有利于水产品干制。     

Far-infrared radiation assisted drying of longan fruit

Oversupply of fresh longan (Dimocarpus longan Lour.) from seasonal production in Thailand needs to be preserved in the form of dried product (exported value of over US$70 million in 2009) to prevent it from being damaged by microorganism. Due to well known limitations of hot air (HA) drying, a new technique of using far-infrared radiation (FIR) in combination with hot air and heat pump (HP) dryers for longan is proposed in this study. Longan with initial moisture content of approximately 84–86% w.b. was dried to about 18% w.b. at the drying temperature of 55 °C in the case of combined FIR-heat pump drying and 65 °C in the case of combined FIR-hot air drying with 80% recycled air. In both cases, the electric power supplied to FIR rods was set at 250, 350 and 450 W. The experimental results are presented in terms of the drying kinetics, dried product qualities (color, shrinkage, percentage of rehydration, water activity, texture, and microstructure) and sensory characteristics of the dried product. The results show that FIR in combination with hot air and heat pump drying increases the drying rate of longan by reducing the drying time. FIR also helps to create more porous structure in dried longan, with porosity increasing with the power supplied to the FIR heaters. The formation of porous structure results in a product with lower shrinkage, improved rehydration, lower hardness and lower toughness than samples dried in the absence of FIR. In addition, the FIR dried longan had a stronger red color and appeared darker. Dried longans obtained by HP, HA, combined techniques and the product from the local market, were all rated similarly by a sensory panel for color, shape, flavor and taste. It is worth noting that the overall energy used for FIR-assisted drying processes decreased with the increase in the power supplied to the FIR heaters.     

山药热泵干燥特性及数学模型的研究

本文以新鲜山药为原料,研究其热泵干燥特性及数学模型。以干燥温度、切片厚度为因素,研究其对山药热泵干燥特性的影响,并通过SAS8.0软件对实验数据进行拟合得出山药热泵干燥模型,得到了山药热泵干燥的干燥特性曲线和干燥速率曲线。干燥温度越高、切片厚度越薄,山药的干燥速率越快,干燥时间越短。干燥温度对山药热泵干燥的速率有较大影响,而切片厚度对干燥速率的影响较小;山药热泵干燥符合Page模型,模型拟合效果很好,经验证,模型预测值与实验值比较吻合,能正确反应山药干燥规律,该模型可以用来描述山药热泵干燥过程变化过程。对热泵干燥山药产品的品质进行分析表明,与热风干燥相比,采用热泵干燥方式山药具有较好的复水性,色泽呈乳白色,感官品质良好。     

不同风干工艺处理的武昌鱼鱼肉品质和风味的变化

以腌制武昌鱼为原料进行干制,通过测定热泵干燥、热风干燥、冷风干燥、联合干燥四种风干工艺处理下的武昌鱼鱼肉脂质氧化理化指标,感官,色泽,质构特性,电子鼻,挥发性风味成分变化,分析不同干燥工艺处理对武昌鱼品质特性和风味变化的影响。热泵干燥的武昌鱼脂质氧化程度更显著,初级产物氢过氧化物含量最高为4mmol/kg,脂质氧化二级产物丙二醛含量最高为0.68 mg/kg,感官评分结果最好（8.6分）、质构表现最好;冷风干燥处理的武昌鱼色泽表现最差,热风、热泵、联合干燥处理的武昌鱼差异较小;热风干燥处理的武昌鱼硬度最大53.96 N、热泵干燥处理的武昌鱼弹性最大;电子鼻检测表明四种干燥工艺处理武昌鱼风味呈现显著性差异（P<0.05）;挥发性风味物质检测发现联合干燥处理武昌鱼挥发性风味物质含量最多21种,热泵处理挥发性风味物质含量最低仅有6种。综上所述联合干燥处理的武昌鱼鱼肉,脂质氧化程度硬度低、弹性好、挥发性风味物质含量多种类丰富。     

The effect of solar drying and heating on the hardness of Phaseolus beans during storage

Small white beans (Phaseolus vulgaris) were dried and heat processed before storage. Water removal in a solar drier was four times faster than conventional field drying in the pods. Heat treatments included particle-to-particle roasting using hot sand, and microwave heating. All samples stored for 212 days at low moisture contents (4–5%) showed a slow rate of hardening at a low temperature of 18°C and a high temperature of 34°C. However, heat treated and control beans became much harder when stored at a humidity of 9% and a temperature of 34°C. Heating and solar drying are effective treatments prior to bean storage, as they greatly reduce moisture to safer levels.     

Pungency levels of white radish (Raphanus sativus L.) grown in different seasons in Australia

White Radish, or daikon (Raphanus sativus) is a popular root vegetable in East Asian countries but there are increasing export opportunities for lower cost agricultural countries such as Australia. The Japanese processing white radish cultivar, Hoshiriso, was grown in spring, summer, autumn and winter on the Central Coast of New South Wales, Australia and accumulation of the characteristic pungent flavour component, 4-methylthio-3-trans butenyl isothiocyanate (MTBITC) during growth was determined. MTBITC concentration was found to be higher in roots grown in autumn and spring than in winter and summer. There was considerable change in MTBITC concentration during growth in all seasons with a maximum concentration occurring 9 weeks after sowing for roots grown in autumn and winter, and after 13 weeks for spring- and summer-grown roots.     

充氮气热泵干燥对秋刀鱼干燥特性和品质的影响

为提高富含多不饱和脂肪酸的海水鱼的干燥品质,实验以秋刀鱼为原料,分别研究热风干燥、空气热泵干燥和充氮气热泵干燥3种干燥方式对半干秋刀鱼的干燥曲线、感官性质、色差、高铁肌红蛋白含量、酸价、过氧化值、硫代巴比妥酸值、挥发性盐基氮值及脂肪酸组成的影响。结果表明:热风干燥半干秋刀鱼的干燥效率高,但干燥品质差,脂肪氧化严重,感官评分最低;空气热泵和充氮气热泵干燥能提高半干秋刀鱼的干燥品质,经充氮气热泵制得产品脂肪氧化程度最低,产品的色泽好,感官评分最高。其酸价为10.01±0.20 mg/g,过氧化值为0.12±0.002 g/100 g,硫代巴比妥酸值为3.15±0.05 mg/kg,多不饱和脂肪酸的保留量为36.13%±4.31%,其中二十碳五稀酸和二十二碳六稀酸保留量为24.78%±2.70%;色差值为11.66±0.52,高铁肌红蛋白的相对含量为26.11%±0.64%。充氮气热泵干燥适用于富含多不饱和脂肪酸的海水鱼的干燥,是制备高品质半干秋刀鱼的理想干燥方式。     

白萝卜间歇微波热风耦合干燥过程干燥特性分析

对比不同的间歇微波功率与热风耦合干燥及间歇微波干燥对白萝卜干燥特性（水分比、有效扩散系数和活化能）、中心与表面温度和颜色的影响。结果表明,有效扩散系数随水分含量的下降先缓慢上升后快速上升,活化能随水分含量的降低先缓慢升高后快速升高,Logistic模型能很好地反映活化能和水分之间的关系,并且单独进行间歇微波干燥的样品的活化能较高。干燥条件设定为间歇比5 s/20 s,热风温度30 ℃的样品其在干燥过程中物料中心温度最低,中心温度与物料表面温度相差最少,且干燥产品颜色最好。     

基于Weibull分布函数的双孢菇热泵干燥特性研究

为提升双孢菇干制品品质,采用热泵式冷风干燥对双孢菇进行脱水处理,以双孢菇热风干燥和冷冻干燥为参照实验,对不同热泵式冷风干燥条件下(进口风速、干燥温度)双孢菇的干燥耗时、干燥能耗、产品硬度以及产品白度进行研究;利用Weibull分布函数对双孢菇热泵式冷风干燥过程中的水分扩散机制进行分析;基于干燥效率指标和产品品质指标,采用加权综合评分法对双孢菇热泵式冷风干燥过程进行评价。实验表明:加快进口风速干燥耗时最小值比最大值降低9.09%,提升干燥温度干燥耗时最小值比最大值降低27.27%;干燥温度对双孢菇热泵式冷风干燥能耗、产品硬度和产品白度影响更为显著(p<0.05);Weibull分布函数能够准确描述(R2>0.99)双孢菇热泵式冷风干燥过程,不同干燥条件下双孢菇冷风干燥的形状参数均小于1,整个干燥主要受内部水分扩散控制;相对于冷冻干燥,双孢菇热泵式冷风干燥耗时及能耗分别降低了50%和26.35%;而相对于热风干燥,冷风干燥技术将双孢菇干制品的产品硬度降低13.44%,同时干制品产品白度提升了59.92%;实验操作条件范围,双孢菇冷风干燥最佳干燥条件为25 ℃干燥温度和2 m/s进口风速。结论:热泵式冷风干燥技术能够提升双孢菇干制品品质同时降低干燥耗时和能耗。     

Effect of postharvest handling on valerenic acids content of fresh valerian (Valeriana officinalis) root

Valerian (Valeriana officinalis) is a medicinal herb native to Europe and North Asia, the roots and rhizomes of which are used as a sedative for nervous tension, sleeplessness, anxiety and stress. The impact of washing and drying on the valerenic acids concentration in valerian roots was investigated. The valerenic acids content of roots that were washed, soaked or cut prior to drying was not significantly different from that of whole valerian roots that were dried without washing, but cutting markedly decreased the drying time. Increasing the drying temperature from 15 to 70 °C reduced drying time by 176 h, with a 23% loss of valerenic acids from 15 to 40 °C. A further 36% loss occurred from 40 to 50 °C but no further significant change was evident at higher temperatures. The use of a heat pump dryer reduced the drying time at 40 °C by 25% compared with a hot air drier operated at the same temperature with no significant difference in the level of valerenic acids. There was no significant change in the level of valerenic acids in fresh whole roots held at ambient conditions for 10 days but a considerable decrease in water content. Hence valerian growers can separate or soak roots prior to washing and can store fresh roots before drying without concern over loss of valerenic acids. However, drying at the lowest feasible temperature is recommended. Copyright © 2005 Society of Chemical Industry     

不同干燥方式对柚子皮粉加工特性及功能成分含量的影响

为探究不同干燥方式对柚子皮粉品质的影响,以广东省梅州市大埔县白肉蜜柚的新鲜外表皮（仅油泡层,厚度1~2 mm）为原料,采用热风、热泵和真空冷冻3种干燥方式分别对其处理得到柚子皮粉,研究不同干燥方式制得的柚子皮粉在加工特性和功能成分含量等方面的性质。结果表明,不同干燥方式制得的柚子皮粉在加工特性和功能成分含量等方面都存在明显差异。其中热风干燥得到的柚子皮粉具有较高的持水率（7.48±0.15 g/g）、持油率（3.63±0.05 g/g）、溶解度（29.18%±0.74%）、溶胀率（536.16%±38.25%）,且析水率较低（0.670±0.008 g/g）,具有较好的冻融稳定性。热风干燥和热泵干燥得到的柚子皮粉含有较高的类黄酮（6.10±0.11、5.93±0.01 mg/g）、多糖（3.57%±0.13%、3.71%±0.09%）和水不溶膳食纤维（43.69%±0.01%、45.55%±0.02%）,真空冷冻干燥得到的柚子皮粉含有较高的果胶（55.86%±0.06%）和水溶性膳食纤维（3.94%±0.17%）。其中热泵干燥得到的柚子皮粉在各方面均处于较好水平,且具有干燥时间短、能耗低等优点,更加适宜工厂大批量生产加工。     

Some quality characteristics of solar-dried cocoa beans in St Lucia

A field comparison of solar drying and open-air sun-drying of cocoa (Theobroma cocoa L) beans was carried out in St Lucia. Four methods of drying (indirect solar drier, direct solar drier, open air/perforated steel surface and open air/non-perforated wooden surface) were examined at three loading rates: 13·7, 26·9 and 40·4 kg m⁻². Beans from the open air had a higher incidence of external mould and poorer external appearance, though differences were minor. Beans dried at the lower rate of 13 kg m⁻² showed the best colour, but the highest titratable acidity. Conversely, beans dried at the higher loading rate of 40·4 kg m⁻² showed significantly lower titratable acidity, but poorer colour. Differences in cut-test score, colour, pH and titratable acidity between the open air and closed driers were small or not significant. While not significant, the indirect drier did show the highest cut-test score and the direct drier the poorest. Beans from the indirect drier were darker and more purple, while those from the direct drier were lighter coloured and less purple. The beans from the direct drier, dried to 6% moisture (WB) were, though not significantly so, more brittle and higher in titratable acidity than those from either the open air or indirect drier. Overall the beans from the indirect drier showed the highest quality and those from the direct drier the poorest. Whether the modest improvement of the indirect drier over the open air driers is sufficient to warrant investment in such a drier is unclear. © 1998 SCI.     

基于综合加权评分法研究不同干燥方法对龙眼肉品质特性的影响

为了提高龙眼肉干制品的品质,采用太阳能辅助热泵干燥、微波真空干燥、热风干燥、热泵干燥等干燥方法对龙眼肉进行干制,并应用综合加权评分法对龙眼肉干制品感官品质、单位能耗、多糖含量等指标进行评价。结果表明:太阳能辅助热泵干燥龙眼肉所测指标的综合加权评分在4种干燥方法中得分最高。该方法可作为最佳干燥方法应用于生产。     

响应面优化仙草微波间歇-热风联合干燥工艺及其对仙草凝胶品质的影响

以仙草为研究对象,采用微波间歇-热风联合干燥方式,探讨微波功率、微波间歇时间、联合干燥转换点含水率及热风干燥温度对仙草多糖提取率的影响,采用Box-Behnken进行优化,并比较不同干燥方式处理仙草对其多糖提取率及凝胶品质的影响.结果表明,通过响应面优化试验获得最优工艺为微波功率为403 W,微波间歇时间为60 s,转...     

Effects of layer arrangement on heating uniformity and product quality after hot air assisted radio frequency drying of carrot

The conventional drying technology prolongs the shelf life of carrots but may cause the serious loss of nutrients. The aim of this study was to investigate the effects of intermittently rearranging layers on the heating uniformity, drying characteristics and quality of carrot slices under the hot air assisted radio frequency (RF) heating. The carrot slices were dried for 270 min using hot air (60 °C) assisted RF heating at the electrode gap of 100 mm firstly, and then followed hot air drying to achieve the final moisture level (0.11 kg/kg (d.b.)). The results showed that the selected hot air assisted RF drying protocol for the carrot slices reduced 30% of the duration compared to the single hot air drying. The carrot slices dried by the combined drying method had the highest total carotenoid value (P ≤ 0.05) except for possessing accepted color and rehydration. Therefore, the combined drying method could improve the drying rate and maintain heat sensitive substances in carrot slices.     

COMAS烘丝机工艺参数与叶丝质量的测试分析

为提高COMAS烘丝机烘后叶丝膨胀效果 ,对影响叶丝膨胀效果的有关工艺参数进行了测试分析。结果表明 :①改变切丝宽度可影响叶丝填充值。高档烟叶丝宽度为 0 .95mm时填充值最高 ;低档烟叶丝宽度为 1.2 0mm时填充值最高。②叶丝填充值随加料后叶片含水率的增大而增大 ,随烘前叶丝温度的增加而增加。③在设备能力范围内 ,叶丝填充值随物料流量的增大而间接增大。④在烘前叶丝含水率和温度一定的情况下 ,增加烘丝机筒壁温度并与适宜的热风温度及热风风速相配合 ,有利于提高烘后叶丝质量。     

Colour,phenolic content and antioxidant capacity of some fruits dehydrated by a combination of different methods

The objective of this study was to improve product quality of dehydrated fruits (apple, pear, papaya, mango) using combined drying techniques. This involved investigation of bioactivity, colour, and sensory assessment on colour of the dried products as well as the retention of the bio-active ingredients. The attributes of quality were compared in regard to the quality of dehydrated samples obtained from continuous heat pump (HP) drying technique. It was found that for apple, pear and mango the total colour change (ΔE) of samples dried using continuous heat pump (HP) or heat pump vacuum-microwave (HP/VM) methods was lower than of samples dried by other combined methods. However, for papaya, the lowest colour change exhibited by samples dried using hot air–cold air (HHC) method and the highest colour change was found for heat pump (HP) dehydrated samples. Sensory evaluation revealed that dehydrated pear with higher total colour change (ΔE) is more desirable because of its golden yellow appearance. In most cases the highest phenol content was found from fruits dried by HP/VM method. Judging from the quality findings on two important areas namely colour and bioactivity, it was found that combined drying method consisted of HP pre-drying followed by VM finish drying gave the best results for most dehydrated fruits studied in this work as the fruits contain first group of polyphenol compounds, which preferably requires low temperature followed by rapid drying strategy.     

滚筒烘丝机控制方法的改进与对比分析

为了解决目前滚筒烘丝机中以筒壁温度控制出口烟丝含水率对产品质量稳定性造成一定影响的问题,对滚筒式烘丝机叶丝干燥去湿控制方法进行了改进:在现有筒壁温度控制模式的基础上增设一套以调节入口热风风量来实现出口含水率自动控制的热风风量控制模式,并且对两种控制模式进行了试验对比,结果表明:①采用热风风量控制模式,出口叶丝含水率和出口叶丝温度的稳定性较好,且含水率和温度的波动范围较小;②采用热风风量控制模式,对叶丝特征尺寸(de)的下降影响程度较小,而叶丝特征尺寸(de)的稳定性较差,且叶丝特征尺寸(de)的波动范围比采用筒壁温度控制模式的波动范围略大;③两种控制模式下的叶丝感官质量差别不大,香气风格一致,在烟气风格特征上略有差别.