An improved method for thin layer chromatographic analysis of saponins

Analysis of saponins by thin layer chromatography (TLC) is reported. The solvent system was n-butanol:water:acetic acid (84:14:7). Detection of saponins on the TLC plates after development and air-drying was done by immersion in a suspension of sheep erythrocytes, followed by washing off the excess blood on the plate surface. Saponins appeared as white spots against a pink background. The protocol provided specific detection of saponins in the saponins enriched extracts from Aesculusindica (Wall. ex Camb.) Hook.f., Lonicera japonica Thunb., Silene inflata Sm., Sapindusmukorossi Gaertn., Chlorophytum borivilianum Santapau & Fernandes, Asparagusadscendens Roxb., Asparagus racemosus Willd., Agave americana L., Camellia sinensis [L.] O. Kuntze. The protocol is convenient, inexpensive, does not require any corrosive chemicals and provides specific detection of saponins.     

油莎豆热风干燥特性及数学模型研究

以新鲜油莎豆为原料,研究风温和风速对油莎豆热风干燥特性的影响,计算干燥过程中有效扩散系数与活化能,并选取8种干燥动力学模型进行拟合分析。实验结果表明：热风温度越高,干燥速率越快,干燥时间越短;风速对干燥速率影响较小。本试验干燥过程主要发生在降速阶段,油莎豆有效水分扩散系数2.2856×10^-10～7.8112×10^-10,平均活化能为35.31kJ/mol,Two-term模型可以很好的反映油莎豆热风干燥过程,实验值与预测值吻合度较高,拟合效果良好。     

滚筒催化红外—热风联合干燥核桃的贮藏特性

以酸价和过氧化值为评价指标,研究不同贮藏温度和时间下核桃氧化酸败反应动力学过程,建立评价不同贮藏温度下核桃货架期的预测模型。结果表明,干燥处理后核桃贮藏期间酸价和过氧化值均随贮藏时间的延长而不断升高。变温滚筒催化红外—热风联合干燥处理的核桃酸价和过氧化值增幅最小,贮藏90 d后酸价为1.27 mg/g,过氧化值为0.019 9 g/100 g,其次是恒温滚筒催化红外—热风联合干燥核桃,最高的为单一热风干燥核桃,但均未超过国家规定标准,且品质良好。核桃的氧化酸败反应符合一级化学反应动力学模型。此外,分别以酸价和过氧化值建立了变温滚筒红外—热风联合干燥核桃的货架期预测模型,其R²＞0.99,相对误差＜9%,表明该预测模型在5~35 ℃内可较好地预测核桃的货架期。     

油菜籽薄层真空干燥技术的研究

油菜籽含有丰富的脂肪、蛋白质和多种维生素,是我国主要的油料作物,同时也是蛋白质作物、饲料作物、能源作物和蜜源作物,综合利用效益高.目前我国油菜籽的产地集中在长江中下游地区,收获季节适逢南方的阴雨潮湿天气,使得油菜籽的干燥和储藏成为加工链中亟须解决的问题.主要研究油菜籽薄层真空干燥技术,为新设备的研制开发及加工链提供必要的数据参考.     

薄层扫描法测定罗汉果糖苷(V)含量的研究

建立采用薄层扫描法测定罗汉果糖苷(V)含量的方法。点样于硅胶G板上,以正丁醇-乙醇-水(8∶2∶3)为展开剂,10 %硫酸乙醇显色,单波长反射法锯齿扫描,λ=5 0 0 nm。罗汉果糖苷(V)在2 .0～16 . 0 μg范围内具有良好的线性关系,r=0 .992 1,平均回收率为97.6 2 % ,RSD为2 .5 9% (n=4 )。该法简便快速、准确灵敏,可用于罗汉果糖苷生产质量监控。     

Novel microwave–freeze drying of onion slices

The present study aimed to introduce the capability of a novel dehydration technique. To do so, slices with various thicknesses (3.5 and 7 mm) of white onions were dried using commercial freeze drier (abs. pressure 0.005 mbar, temp. 45 °C), our own designed microwave-vacuum drier (abs. pressure down to 300 mbar) under various microwave powers (120–1200 W) and microwave-vacuum–freeze drier (onion slices kept at −20 °C for 2 h). Then, their dehydration rates and some quality parameters, such as rehydration ratio, colour ( L*, a* and b* ) and micro-structure were investigated. Our findings showed that microwave-vacuum–freeze drier is practically a rapid, simple, efficient, economic and novel dehydration technique which can be used for dehydration of mainly foodstuffs. The quality properties of slices produced by this novel method were also completely comparable and competitive with commercial freeze drier with over 96% saving on processing time and enormous amount on energy and capital investments.     

核桃滚筒催化红外—热风干燥试验及能耗分析

为了提高硬壳坚果类产品干燥效率,在研制的滚筒式催化式红外干燥设备基础上进行核桃红外干燥试验,考察工艺参数对脱水率、颜色和开壳率的影响。将滚筒催化红外—热风联合干燥和单一热风干燥作比较,对二者的干燥时间、干燥曲线、干燥速率曲线和能耗进行对比分析。研究结果表明,催化红外温度、距离和滚筒转速均对干燥效果和产品品质有显著影响,先在最佳的距离30 cm、温度450 ℃、滚筒转速1.5 r/min条件下滚筒催化红外预干燥9.5 min,然后在温度43 ℃、风速3 m/s条件下热风干燥16 h,与单一热风干燥（20 h）相比,显著提高了干燥速率,缩短了19.2%的干燥时间,节约了11.6%的能耗,且干制核桃的品质良好。     

洋葱真空远红外薄层干燥模型

在真空远红外环境下对洋葱进行了薄层干燥试验,对实验数据进行统计分析,建立了薄层干燥数学模型。结果表明,预测值与实测值一致性较好,所建数学模型可用于描述洋葱真空远红外薄层干燥。     

Stability of quercetin derivatives in vacuum impregnated apple slices after drying (microwave vacuum drying,air drying,freeze drying) and storage

Microwave vacuum drying (MVD) was investigated for apple slices enriched with quercetin derivatives by vacuum impregnation (VI). Additional freeze drying (FD) and air drying (AD) were conducted. Compared to native apples, the impregnated tissue resulted in higher moisture content, elevation of weight and significant browning, due to the incorporated VI solution. The total quercetin content and quercetin glycoside composition were not affected by MVD and FD. The vacuum conditions protect the polyphenols from oxygen dependent degradation and browning reactions. AD resulted in an average quercetin glycoside loss of 44% and undesirable changes, particularly discoloration. The degradation is caused by both non-enzymatic and enzymatic reactions. The pulsed microwave energy intake improved the drying result in structure and led to a faster drying process of 130 min. The bulk density of MVD apple chips (0.69 g/ml) ranged between 0.33 g/ml for FD and 0.75 g/ml for AD. The final moisture content was the lowest after FD (6.8 g/100 g), followed by 9.0 g/100 g after MVD and 12.7 g/100 g after AD. The shelf life was significantly influenced by storage temperature and time. After 12 month at 20 °C, the total quercetin content decreased by 21%.     

三华李果糕热风干燥特性及数学模型的建立

利用洞道式热风干燥装置,探讨不同的热风温度对三华李果糕干燥水分比MR和干燥速率v的影响。采用非线性回归法将7种常见薄层干燥数学模型与实验数据进行拟合,并追加验证实验。结果表明:三华李果糕热风干燥是内部水分扩散控制的降速干燥过程,且干燥温度不宜高于70℃。比较各模型的决定系数R2,卡方X2和标准误差eRMSE,Logarithmic模型能较好地描述和预测三华李果糕的干燥过程,其干燥动力学方程为:MR=1.0915exp[-（0.51093-0.01497T+0.00016T2）·t]-0.13348。      

Study the effect of sun, oven and microwave drying on quality of onion slices

Sun, oven (50 and 70 °C) and microwave oven (210 and 700 W) drying of onion slices were carried out to monitor the drying kinetics and quality degradation of the product. Page, “Modified Page” and “Midilli and Küçük” models exhibited high coefficient of determination (R²) values, ranging between 0.994 and 0.999. The calculated effective diffusivity (D_eff) values (m²/s) of onion slices for the sun, oven 50 °C and oven 70 °C, microwave 210 W and microwave 700 W drying process were 8.339 × 10⁻¹⁰, 7.468 × 10⁻¹⁰, 1.554 × 10⁻⁹, 4.009 × 10⁻⁸ and 4.869 × 10⁻⁸, respectively. Fresh and dried onion slices had high amounts of K (696.82-16357.55 mg/kg), Ca (69.64-340.03 mg/kg), Na (37.72-1895.43 mg/kg), Mg (3.31-964.77 mg/kg) and P (46.47-3384.07 mg/kg) minerals. The highest mineral values were determined in oven dried samples. Sun (L^∗ 58.00 ± 4.83, a^∗ 0.27 ± 0.10, b^∗ 14.36 ± 2.40) and microwave oven drying (210 W) (L^∗ 54.78 ± 7.54, a^∗ −0.71 ± 0.09, b^∗ 13.17 ± 1.05) revealed better colour values in the dried products. The phenolic contents of microwave oven dried samples (1664.39 ± 134.12 and 1623.59 ± 140.02 for 210 W and 700 W, respectively) were higher than those of the other dried onion slices.     

Short communication: A new mathematical model for thin layer drying of fruits

The aim of this study was to fit a new mathematical model on the thin layer drying curves of fruits. Thin layer drying studies at different temperatures (60, 80 and 100 °C) were carried out on two varieties each of kiwifruit and apricot. The new model was compared statistically with three other drying models (Henderson and Pabis, Page and logarithmic) published in the literature. The proposed equation gave the highest coefficient of determination for both varieties of kiwifruit and apricot and closely followed by the Page equation. Statistical evaluation of the experimental and predicted moisture ratio showed that the proposed equation consistently gave the lowest reduced Chi‐square, root mean square error and mean relative percentage error. The results indicate that the proposed equation has the best curve fitting ability for both fruits. However, there is no theoretical basis offered for the good curve fitting ability of the equation.     

微波和热风联合干燥薄层黄花菜的方法研究

在薄层黄花菜干制工艺中,选择的干制方法直接影响物料干燥时间的长短和产品质量的好坏.为了确定干燥薄层黄花菜的最佳干制方法,以湖南黄花菜的主栽品种鲜猛子花为材料,用热风干燥箱将受试材料在60、70、80、90℃及100℃等干燥温度条件下和用微波炉在高、中及低功率条件下进行干燥试验.结果表明热风干燥温度小于80℃时,干燥时间长(3.5～4h),生产效率低,但产品质量好;干燥温度大于90℃时,干燥时间短(1.5～2h),生产效率高,但产品质量差,因而薄层黄花菜的最佳干燥温度为90℃;与热风干燥相比,无论哪种微波功率干燥时间都较短,但产品质量差;先微波干燥再热风干燥可显著缩短干燥时间,但产品质量不好,先热风干燥再微波干燥不但明显地缩短干燥时间,而且可保证产品质量.同时建立了黄花菜薄层干燥的数学模型MR=(r=e-4.3154+0.05631T,n= 0.5228+ 0.01007T), 可较好地描述干燥过程中物料含水率与干燥时间的关系.     

真空微波与热风联合干燥蒜片的工艺研究

运用正交实验对四种无硫护色液进行复合实验,最佳护色组合为：CaCl2浓度为0.6%、NaCl浓度为0.8%、L-半胱氨酸浓度为0.10%,经此复合护色液护色得到干燥蒜片L＊值为86.23。比较了热风、真空微波、真空微波与热风联合干燥三种生产工艺所得蒜片干制产品的品质,采用正交实验优化了热风与真空微波联合干燥蒜片的生产工艺。结果表明：前期采用真空度-90kPa,微波功率375W,微波干燥20min,后期60℃热风干燥60min,干燥总时间为80min,缩短了热风干燥时间,得到了高品质的蒜片产品。     

魔芋薄层干燥试验及数学模型的建立

在对魔芋进行三因素三水平薄层干燥试验的基础上,分析了热风温度(50、60、70℃)、风速(0.75、1.45、1.95 m/s)及芋片厚度(5、6、7 mm)对魔芋干燥速率的影响。试验表明,魔芋干燥时间随着热风温度的升高、风速的增大以及芋片厚度的减小而减少,且热风温度对魔芋干燥速率的影响最显著;用三个经典数学模型(Henderson and Pabis,Lewis和Page模型)及三次多项式模型对试验数据进行拟合,经拟合得出最适合魔芋干燥的模型为三次多项式模型;用BP神经网络建立魔芋干燥的数学模型,并与三次多项式模型的拟合结果进行对比,结果表明,BP神经网络拟合的含水率比平均相对误差为0.94%,精度明显高于三次多项式模型(5.64%)。     

苹果片红外热风联合干燥特性研究

以苹果为原料,研究不同红外辐射距离和热风温度下苹果片的干燥特性,并对苹果脆片的干燥时间、色泽、硬度、脆度和复水性进行分析。结果表明,在苹果片红外-热风联合干燥过程中,热风温度对干燥时间和脆片品质影响显著;干燥过程为降速干燥,水分有效扩散系数范围在2.92×10^-88.85×10^-8m²/s内,且随热风温度升高而增大;苹果片干燥活化能为75.67 k J/mol。苹果片在红外辐射距离50 mm,辐射功率1500 W,热风温度80℃,风速0.8 m/s的条件下,干燥时间仅162 min,并具有良好的色泽（L*值75.01,a*值8.92、b*值32.97）和质构（硬度1063.66 g,脆度0.531 s）。先红外后热风的联合干燥方式能有效抑制酶活和提高干燥速率,以及改善产品品质。      

Influence of pre-treatments on microbial load of stored dehydrated onion slices

Onions slices were pre-treated in potassium meta-bisulphite (KMS) and sodium chloride with different concentration levels to study the microbial load of tray and greenhouse-dried onion slices up to 6 months of storage. Data were analysed as per procedure of one-way classified anova using DMRT of AgRes statistical package for bacteria, yeast, fungi and Lactobacilli . Results revealed that in almost all samples, permissible levels of bacteria [18.33 × 10¹ colony-forming units (CFU) per gram], yeast (ND), fungi (0.5 × 10¹ CFU g⁻¹) and Lactobacilli (0.25 × 10¹ CFU g⁻¹) were observed after 5 months of storage. All the samples were also found to be free from Escherichia coli and no Mac Conkey growth was noticed. Onion slices pre-treated in 0.25% and 0.50% KMS and dried in tray and greenhouse, respectively, were found best after 6 months of storage period.     

脱水马兰加工特性的研究

通过在不同风温（52℃、56℃、60℃）和不同微波输出功率（150W、225W和300W）条件下对马兰进行脱水干燥试验，结果表明，热风干燥时间较长，效率较低，微波干燥随着输出功率的提高干燥率也相应增加，利用微波干燥可以从热风干燥可以从热风干燥所需的200－400min缩短到5－8min，同时，微波干燥能更好地保持马兰的色泽，并有更高的复水性。     

芒果切片热风干燥特性及模型

目的：为对芒果热风干燥过程进行预测与控制。方法：以新鲜金煌芒为试验材料,研究热风温度（60,65,70 ℃）和芒果切片厚度（0.8,1.0,1.2 cm）对芒果热风干燥曲线、干燥特性曲线、水分有效扩散系数等的影响,并选取常用的适用于果蔬的6种干燥模型进行拟合、分析及验证,选出最适合芒果热风干燥的模型。结果：随温度的升高,切片厚度的减小,加快了芒果片的干燥速率,所需的干燥时间越短。水分有效扩散系数随温度和厚度的增大而增大,为1.401 39×10^-10～3.655 46×10^-10 m²/s。Logarithmic模型的R²最大、X²和RMSE最小,分别为0.998 87,0.000 124 779,0.001 37。结论：Logarithmic模型预测值与试验值验证基本吻合,可以较好反映芒果片在干燥过程中水分含量的变化规律。