黄秋葵真空干燥行为及干燥参数的响应面试验优化

为得到品质较高的黄秋葵干制品,采用真空干燥处理黄秋葵,直至其水分含量低于（5±0.5）%（湿基含水率）。采用含水率、复水比、灰度、总色差以及VC含量等指标来评价黄秋葵真空干燥过程中的品质特性,并通过非线性拟合得到适用于黄秋葵真空干燥的水分比变化的数学模型。为得到干燥速率快、品质高的干燥参数,以干燥温度、系统压强和切片厚度为试验因素,以干燥速率和VC含量为指标对黄秋葵真空干燥参数进行响应面试验优化。此外,采用模糊数学法对最佳干燥参数条件下的黄秋葵干制品进行感官评定。结果表明：Logarithmic模型能够描述出黄秋葵真空干燥过程中水分比的变化规律;干燥温度、系统压强、切片厚度分别为60 ℃、18 kPa和10 mm时黄秋葵综合加权评分值最高为0.911,该干燥条件下黄秋葵真空干燥的平均干燥速率和VC含量分别为1.059 kg/（kg·h）和8.315 mg/100 g干物质,均处于一个较高的水平。同时,通过模糊数学分析发现最佳参数组合条件下的产品能够被消费者接受。     

Compositional analysis and viscosity measurements of commercial oat brans

Chemical analysis of commercial oat brans (n=10) collected from five different countries showed wide variations in the contents of starch (40–61%), crude protein (9·6–21%), crude fat (8·2–12%), ash (2·0–4·1%), dietary fibre (10·7–19·4%) and mixed-linkage β-glucan (4·7–8·3%). A significant correlation (r=0·83; P<0·005) between the contents of total and extractable mixed-linkage β-glucan was found. Reproducible increases in viscosity were noted for all samples when the finely ground samples were dispersed in phosphate buffer and viscosity development was followed for 100 min. Addition of mixed-linkage β-glucanase greatly reduced the viscosity. Addition of amyloglucosidase, with no detectable mixed-linkage β-glucanase activity, increased viscosity, which could be related to an increased solubilisation of mixed-linkage β-glucan. Highly significant correlations (r>0·90) were found between the contents of both total and extractable mixed-linkage β-glucan and viscosity after dispersion. © 1998 SCI.     

Drying Conditions and Processability of Dried Rapeseed

The possibility of using the oil-point and compression tests for evaluation of dried rapeseeds processability was examined. Seeds of initial moisture 10, 14, 18 and 22% (w/w) were dried at 60, 80, 100 and 120°C to a final moisture of 6·5% (w/w). The values of pressure ( P ₀ ), work ( L ₀ ) and strain (ε₀) determined by the oil-point test, and pressure at strain ε=0·45 mm mm⁻¹ ( P_ε ) and degree of elasticity ( D ) determined by the compression test for bulk dried seeds differed markedly from those found for non-dried seeds. The P ₀ , L ₀ and P_ε values were strongly correlated with the initial moisture of rapeseeds and drying temperature. All the strain values (ε₀) were lower than those for non-dried seeds, and their changes depended solely on the initial moisture of seeds. Changes in the degree of elasticity were irregular and did not reach the value characteristic for overdried seeds, ie 100%. High correlation of the agglomeration test data (Δ_1–3 values) with those of the P ₀ , L ₀ and P_ε made it possible to develop appropriate equations that proved the usefulness of the variables for determining the dried rapeseed processability.     

Processing and consumer acceptance of fruit leather from the unfertilised floral parts of jackfruit

A fruit leather was developed from the unfertilised floral parts of jackfruit. The characteristics of the leather were as follows: moisture 12·26%, fat 0·26%, protein 2·85%, crude fibre 6·27%, ash 0·87%, pH 4·8, titratable acidity 0·0005 meq NaOH g⁻¹, vitamin C 0·023 mg ascorbic acid per 100 g, caloric value 440 kcal per 100 g and water activity 0·6. The colour was bright yellow. Microbial count of the leather was low throughout the storage period. The fruit leather was most stable when packaged in laminated aluminium foil (LAF) during storage. Sensory evaluation showed that samples were acceptable by the panelists. A market survey showed that the fruit leather was slightly better accepted by the consumer at large than laboratory sensory panelists, especially by male respondents and from ethnic Indians. However, more work is needed to further improve the new fruit leather. © 1997 SCI.     

Chemical evaluation of the effect of roasting on the nutritive value of maize (Zea mays, Linn.)

This study reports on the effects of roasting on the chemical composition of maize (Zea mays). Proximate analysis showed no significant difference (p > 0·05) between raw and roasted maize in ether extract, crude protein, crude fibre, ash and carbohydrate content; except moisture content (p < 0·05), which showed a 42·3% decrease. Elemental composition analysis showed decreases of potassium (13·8%) and calcium (41·1%). Significant differences (p < 0·05) were observed for vitamins B₁, B₂ and C contents with 26·8%, 32·4% and 35·1% destruction, respectively. Amino acid analysis showed losses for lysine (26·7%), iso-leucine (20·8%) and leucine (23·4%).There was significant (p < 0·05) variation in phytic acid, oxalic acid, tannin and hydrocyanic acid with reductions of 15·4%, 6·02%, 51·3% and 34·6% respectively.The effect of these changes on the nutritive value of roasted maize is discussed.     

香菇热风干燥工艺优化及其对主要营养物质和抗氧化活性的影响

以香菇为原料,通过单因素试验测定不同切片厚度、热风温度及装载量条件下香菇的干基含水率、水分比及干燥速率变化,通过三因素三水平的响应面试验对热风干燥的工艺参数进行优化,比较香菇在热风干燥前后可溶性蛋白质、总酚含量及1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除率的变化。结果表明:单因素试验中切片厚度在3~12 mm、热风温度在50~70℃、装载量在5~15 g/dm2范围时香菇干基含水率、水分比及干燥速率较合适;响应面试验优化后各工艺参数的最佳组合为切片厚度4.99 mm、热风温度55.21℃、装载量7.88 g/dm2;经热风干燥后香菇的可溶性蛋白质及游离氨基酸含量无显著下降,而总酚含量及DPPH自由基清除率都较干燥前显著降低,说明热风干燥可以较好保留香菇中可溶性蛋白质和游离氨基酸含量,但对香菇总酚含量及抗氧化活性的破坏较大。     

Drying kinetics and effective moisture diffusivity of bamboo shoot slices undergoing microwave drying

Effect of microwave power on moisture content, moisture ratio, drying rate, drying time and effective moisture diffusivity (D_eff) of bamboo shoot was investigated using microwave drying. To study the effect of microwave power on drying, bamboo shoot samples (250 g) were dried at different power levels ranging from 140 to 350 W. To determine the kinetic parameters, drying data were fitted to various models based on the ratios of differences between initial and final moisture contents and equilibrium moisture content. Among the models proposed, Wang and Singh model gave a better fit for all drying conditions used. By increasing microwave output power, the D_eff values increased from 4.153 × 10^?10 to 22.835 × 10^?10 m² s^?1. A third‐order polynomial relationship was found to correlate the D_eff with moisture content. Further scope of this research work would include the effect of certain factors (shrinkage, case hardening, distortion of product and shape of bamboo shoot samples as an infinite slab) of practical significance to improve the model.     

Mathematical modeling of thin-layer drying kinetics and moisture diffusivity study of apple slices using infrared conveyor-belt dryer

The drying features of apples at different infrared drying settings were investigated. The drying time, moisture-effective diffusion, and activation energy of infrared dried apples were measured experimentally and statistically as a function of slice thicknesses, radiation intensity, and air velocity. The infrared intensity of 0.225, 0.130, and 0.341 W/cm², slice thicknesses of 6, 4, and 2 mm, and airflow of 0.5, 1.0, and 1.5 m/s were used to dry apple slices. The data shows that the drying time reduced as IR increased, but airflow and slice thickness increased. Eight statistical factors were used to compare 11 alternative mathematical drying models. The experimentally acquired drying curves were matched to the thin-layer drying equations. According to the calculations, the Midilli et al. equation had the greatest (efficiency and R²) and lowest (χ², sum of squared errors, standard error of estimate, standard error, standard deviation of difference) values. As a result, this equation is the best for modeling the drying curves of apple slices across all drying circumstances. The optimum moisture diffusivity value varied from 2.59 to 9.07 × 10⁻¹⁰ m²/s. The mean activation energy was determined to be 19.02–29.83 kJ/mol under various experimental conditions.     

Cassava and soyabean flours and resting time effects on sensory and physical characteristics of reconstituted miondo

Sensory and physical characteristics of miondo made with three types of cassava flour (CF) (CF1, shredding of roots and drying; CF2, shredding of roots, 24-h natural fermentation, and drying; CF3, 3-day steeping of roots and drying) containing 0, 5 and 10% of added soybean flour (SF) were evaluated after 0, 1, 2, 3 and 4 h of resting (RT) before cooking to determine the optimum CF and SF levels and RT. Results indicated that miondo made with CF3 were more palatable (P<0·05) and firmer (P<0·05) than those of CF1 and CF2. Upon resting, there was no significant changes in sensory characteristics of cooked miondo, although the instrumental firmness (hardness) of miondo (made with CF3) increased (P<0·05). Upon addition of SF, products became less palatable, more yellow in colour, softer, less sticky; weight loss of raw miondo decreased; water retention ratio (WRR), crude protein contents, and total ashes of CF3 increased. WRR and protein content of CF3–SF blends correlated negatively with hardness of miondo (r=-0·90 and -0·99, respectively). CF3 with no added SF was most appropriate for making palatable miondo, regardless of the resting time. © 1998 SCI.     

Spray Drying of Spinach Juice: Characterization,Chemical Composition,and Storage

The 1st aim of this study is to determine the influence of inlet and outlet air temperatures on the physical and chemical properties of obtained powders from spinach juice (SJ) with 3.2 ± 0.2 °Brix (°Bx). Second, the effect of 3 different drying agents (maltodextrin, whey powder, and gum Arabic) on the same properties was investigated for the selected inlet/outlet temperatures (160/100 °C) which gives the minimum moisture content and water activity values. For this purpose, the total soluble solid content of SJ was adjusted to 5.0 ± 0.2 °Bx with different drying agents. Finally, the effects of different storage conditions (4, 20, and 30 °C) on the physical and chemical properties of spinach powders (SPs) produced at selected conditions were examined. A pilot scale spray dryer was used at 3 different inlet/outlet air temperatures (160 to 200 °C/80 to 100 °C) where the outlet air temperature was controlled by regulating the feed flow rate. Results showed that the moisture content, water activity, browning index, total chlorophyll, and total phenolic contents of the SP significantly decreased and pH and total color change of the SP significantly increased by the addition of different drying agents (P < 0.05). In addition, the changes in the above‐mentioned properties were determined during the storage period, at 3 different temperatures. It was also observed that the vitamin C, β‐carotene, chlorophyll, and phenolic compounds retention showed first‐order degradation kinetic with activation energy of 32.6840, 10.2736, 27.7031, and 28.2634 kJ/K.mol, respectively.     

Microwave drying of lucerne and grass samples

Microwave drying of fodder crop samples appeared to be a suitable technique, especially when the organic components are to be determined. Eleven lucerne and 17 pasture grass samples were dried by both oven drying at 80°c and microwave drying. The dry matter content of the samples dried by microwaves was 0·8% higher on average than that of the oven-dried samples; the carotene and xanthophyll contents were almost twice as high in the samples dried by microwaves. The digestibility coefficient of the organic matter, determined in vitro, was 1·6 units lower on average in the oven-dried samples; this was due partly to the higher crude fibre content and much lower content of soluble carbohydrates in these samples. There were no significant differences in the total ash and crude protein contents of the samples dried by the two methods. A 500 g sample of fresh grass can be dried in 10 min in the microwave energy apparatus; the moisture content of about 10% obtained after drying guarantees a good grinding and storage ability of the samples.     

姜片热风干燥模型适用性及色泽变化

为研究姜片的热风干燥特性,以姜片厚度、热风温度、热风风速3 个干燥条件为变量,考察其对姜片干燥特性的影响,将不同干燥条件下姜片的水分比、干燥速率进行比较并建立模型。结果表明：姜片的热风干燥以降速过程为主,而且姜片的水分比MR下降的速率随着热风温度、风速的增加而变快,随姜片厚度的增加而变慢。本实验选用常用的8 个薄层干燥模型进行拟合,经拟合后选择Modified Page模型作为姜片干燥过程的最优模型,解出模型为MR=exp[－（kt）n],其中k=－0.023 85＋0.000 505T＋0.023 38V－0.004 993L,n=1.318 307＋0.003 016 5T－0.204 05V－0.002 859L,式中T为干燥温度（℃）;V为热风风速（m/s）;L为姜片厚度（mm）。此模型的平均R2值是0.997 9、χ2最小值是0.000 4、RMSE最小值是0.012 2。模型求解后,以模型外的实验组数据验证表现出较好的拟合度。姜片的有效水分扩散系数Deff随干燥温度、物料厚度、风速的增加而增加,且其值在1.763×10－8～1.054×10－7 m2/s之间变化,活化能为Ea=35.23 kJ/mol（R2=0.948 0）。此外还对姜片在干燥前后的色差进行了测定和分析。     

Effect of Drying and Roasting on the Quality Attributes of Fufu Powder

Abstract

The effect of drying and roasting on the physicochemical and sensory qualities of fufu powder were investigated. The four samples of fufu: cooked dried fufu, cooked roasted fufu, dried fufu slurry and roasted fufu slurry, respectively, were subjected to physicochemical and sensory analysis. The water binding index, water solubility index, and water absorption index, varies between 3.44 and 0.17 (g/g sample), 0.07 and 0.01 (g/g), and 4.73 and 0.83 (g/g) respectively, while the starch damage and amylose content varies between 50.8% and 0.4%, 10% and 13% respectively, with roasted fufu slurries recording the highest values. The proximate composition of dried and roasted fufu samples showed the values of fat (0.6%–0.4%), protein content (0.2%–0.1%), ash content (37.8%–1.0%), moisture content (8.2%–10.2%), crude fibre (1.25%–8.5%) and carbohydrate content (43.0%–84.65%) respectively. Generally, there were no appreciable differences in the proximate composition of dried fufu samples. The pasting temperature of fufu samples varies from 78 to 95°C with roasted fufu slurries recording the highest values. The peak viscosity of dried fufu samples ranges between (80 and 900BU) and viscosity at 50°C ranges between (260 and 460BU). There are no significant differences (P > 0.01) for the sensory qualities in term of color, taste, and overall acceptability except for odor and texture at (P < 0.01).     

Drying and conservation conditions of pollen

In this study, drying and conservation conditions of pollens (for Anzer Honey) were experimentally investigated, and the general drying curve equation was derived by applying the Least Squares Method. Drying experiments were conducted in solar‐ and electric‐assisted dryers. Pollens were placed on the shelves as 50 each g in a single layer having a depth of 2.5 mm. During the drying experiments, the shelf temperatures of the drying cupboard were regulated between 40 °C and 45 °C. Weight losses, moisture contents and mass shrinkage of pollens and average temperatures in the shelves were determined and calculated based on drying time. Additionally, the experimental uncertainty values were calculated as approximately 18%, depending on the experimental results. It was concluded that pollens should be dried at temperatures between 40 °C and 45 °C for between 2.5 and 3 h so as not to change the colour, flavour, smell and structure, and conserved in brown bottles under vacuum in a shady medium. © 2000 Society of Chemical Industry     

红心火龙果热风干燥动力学模型及品质变化

为提高红心火龙果干燥效率及产品品质,研究了不同火龙果片厚度（6、8、10、12?mm）和干燥温度（50、60、70、80?℃）条件下火龙果片干燥特性和品质变化。结果表明：厚度越小,干燥温度越高,火龙果片的干燥速率越快,干燥时间越短。通过模型拟合发现,Page模型能够较好地反映热风干燥过程中火龙果片水分比随厚度和干燥温度的变化。红心火龙果片有效水分扩散系数在3.537?4×10－10～19.942?6×10－10?m2/s之间;厚度为6、8、10、12?mm时,对应的活化能分别为32.985?7、27.086?1、26.889?4、17.792?9?kJ/mol。在干燥温度70?℃、切片厚度6?mm、干燥时间6?h下,火龙果片的总酚含量和抗氧化能力较高。干燥温度和切片厚度对火龙果片色泽影响不明显。     

Study of the nutritional value of black cumin seeds (Nigella sativaL)

The nutritional value of five samples of black cumin seeds from five different sources available in the local market were studied. The average values of the proximate analysis on dry matter basis were 216 g kg⁻¹ for crude protein, 406 g fat, 45 g ash, 84 g crude fibre and 249 g of nitrogen-free extract, whereas moisture content was 38 g kg⁻¹. The mineral and vitamin analyses showed that black cumin seeds contained iron, (105 mg kg⁻¹) copper (18 mg), zinc (60 mg) phosphorus (527 mg), calcium (1860 mg), thiamin (15·4 mg), niacin (57 mg), pyridoxine (5·0 mg) and folic acid (160 μg). The protein quality of black cumin seeds was evaluated using net protein utilisation (NPU), protein efficiency ratio (PER) and net dietary protein energy percent (NDPE %) for two samples imported from Syria and Turkey, while PER was determined for the Syrian sample only. The results indicated that the NPU standardised of Turkish black cumin seeds was significantly higher than that of Syrian type (P<0·05). The mean results (±SD) were 54·6±2·72 for the Syrian type and 63·1±3·74 for the Turkish type. The NDPE% mean results (±SD) were 5·3±0·79 and 5·6±0·26 for the Syrian and the Turkish samples, respectively. The PER adjusted value for the Syrian samples was 1·9. The results of protein quality evaluation and those of the nutrient composition suggest that black cumin is of relatively good nutritional value. © 1998 SCI.     

INFRARED AND HOT-AIR DRYING OF ONIONS

The combination of infrared (IR) and hot‐air drying of onion slices was explored, and the effects of processing conditions such as drying temperature, slice thickness, air temperature and velocity on onion slice characteristics were studied. The onion slice quality was evaluated on the basis of the color and the pyruvic acid content, an index of flavor. Drying of thin slices of onion (2 mm) at low temperature (60C) with a moderate air velocity (2 m/s) and air temperature (40C) retained greater flavor and color. An empiric equation developed to correlate the drying process variables and the onion slice moisture with the drying time provided a good fit (R² = 0.92). Similar equations developed to correlate the drying process variables and the drying time with the pyruvic acid content provided an excellent fit (R² = 0.96), while the equations fit for the total color change of onion slices were satisfactory (R² = 0.86). Combination drying resulted in shorter drying process time and in better onion slice quality as compared to IR and hot‐air drying applied individually.     

Drying behaviour of hazelnuts

A diffusion-based drying model has been used to model the single-layer drying of whole hazelnuts (hull, air-gap and kernel). The drying of whole hazelnut was simulated by means of the numerical solution of Fick's second law for a composite solid consisting of an air gap which is between two solid bodies. The Crank–Nicholson implicit numerical method has been applied to solve the diffusion equation with variable mass diffusivity for whole hazelnut. The numerical data so obtained has been presented in the form of a series of curves which represent the drying characteristics of a whole hazelnut. Experimental results from whole hazelnuts were correlated with the theoretical results. A correlation describing the diffusivity of the whole hazelnut with moisture content and temperature was established, when the expression of diffusivity for hazelnut was used. Predicting the drying behaviour of the hazelnut for a known value of initial moisture content, equilibrium moisture and equivalent radius, a good agreement was obtaind between the experimental data and prediction. Whole hazelnut diffusivity was determined at 25–45°C, air velocity 0·2–0·3 ms⁻¹, 60% relative humidity of air, using the theoretical curves that best fit the data. The diffusivity of whole hazelnut was determined as a function of drying air temperature and velocity. © 1998 SCI.     

山药切片真空干燥特性及模型研究

为了探究山药切片的真空干燥特性,建立干燥模型.在不同干燥温度(40、50、60、70、80 ℃)、真空度(0.03、0.04、0.05、0.06、0.07 MPa)和切片厚度(2、4、6、8、10 mm)条件下进行真空干燥试验,分别利用BP神经网络模型和Weibull分布函数拟合试验数据;并计算有效水分扩散系数、干燥活...     

Influence of drying treatments on the physical and chemical properties of cucumber

This work aimed at determining the properties of cucumber exposed to convective air drying and freeze-drying. The samples were analysed in terms of colour, texture, chemical properties (moisture content, fibre, ash, vitamin C and sugars), phenolic compounds and antioxidant activity in fresh and after drying. The trials in the convective chamber were done at 40 and 60 °C, in the drying tunnel at 60 °C and in the freeze dryer at ?50 °C. The results showed that the antioxidant activity and the phenolic compounds were not affected by any of the drying treatments tested, since the values were quite similar in the fresh product as compared to the dried cucumbers. With respect to colour, the freeze drying treatment was identified as the one originating less colour change, when compared with the colour of the fresh product. Finally, texture was less affected by drying in the chamber at 40 °C and freeze drying.