The effect of low-temperature blanching on the quality of fresh and frozen/thawed mashed potatoes

The effect of low‐temperature blanching (LTB) prior to cooking on colour, textural, firmness and oscillatory parameters, sensory attributes and overall acceptability of either fresh or frozen/thawed mashed potatoes was studied using response surface methodology (RSM) to establish the optimum temperature and time for blanching in both types of mashed potatoes. A central composite rotatable design was used to study the effects of variation in levels of blanching temperature (57.93–72.07 °C) and time (15.86–44.14 min) on the quality parameters. Stationary points showing maximum thickening had critical temperatures (approximately 67–69 °C) and times (approximately 26–30 min) in the ranges of temperature and time used for each independent variable for both fresh and frozen/thawed mashed potato. Results showed a high correlation between structural reinforcement and overall acceptability under optimum experimental blanching conditions. This demonstrates the potential of this experimental approach in terms of tailoring physical properties to predetermined levels in order to meet consumer preferences in mashed potatoes, and of altering the changes that occur after freezing and thawing.     

南极磷虾酶解液氯化钙法脱氟工艺的研究

为解决南极磷虾酶解液氟含量过高问题,以脱氟率为指标,利用响应面法对南极磷虾酶解液氯化钙法脱氟工艺进行优化。优化结果表明,在氯化钙添加量1.38%,初始pH9.0,反应温度20℃时,脱氟率达到89.43%。而且,氯化钙法脱氟过程对酶解液氨基氮、总氮的影响都不显著,是一种较为理想的脱氟方法。     

The effect of addition of calcium and processing temperature on the quality of guava in syrup

The effect of process temperature and calcium concentration in the cooking syrup of guava in syrup were studied. A central composite rotatable design (CCRD) was used to optimize the quality indices of the final product, such as texture and colour. All of the processed guava quality parameters were compared with those of the fresh fruit and of a commercial sample to evaluate the effects of processing on the final product quality. Increase in the process temperature promoted changes in the final product colour, the fruit becoming darker. On the contrary, higher calcium concentrations in the cooking syrup produced lighter samples, with colour parameters closer to those of the fresh fruit. In general, the addition of calcium promoted better texture and minimized the negative effects of temperature on the mechanical properties. Processed guavas had higher rupture stress and strain than fresh fruit, indicating an increase in hardness and elasticity.     

响应面优化单溶剂体系棉酚提取工艺研究

为了降低棉粕的毒性及最大限度地提取棉酚,以棉仁为原料,以甲醇为溶剂,采用溶剂浸出法对棉仁中游离棉酚的提取工艺进行研究。在单因素试验的基础上,通过响应面法对工艺条件进行优化。结果显示各因素影响游离棉酚提取率的主次顺序为:提取时间料液比提取温度搅拌速率;得到的最佳工艺条件为:料液比1∶24,提取温度35℃,提取时间42 min,搅拌速率2 600 r/min,提取次数2次(即先以料液比1∶12提取,提取21 min,再以料液比1∶12提取,提取21min);在最佳工艺条件下,游离棉酚的提取率为68.9%±0.81%,其纯度为81.9%±0.85%。此时,棉粕中游离棉酚残留量为839.7 mg/kg,小于饲料卫生标准(GB 13078—2001)中所规定的棉籽饼、粕中允许的游离棉酚最大残留量1 200 mg/kg。     

响应曲面法优化白豆蔻中钙的测定条件

利用响应曲面法优化火焰原子吸收光谱法（FAAS）测定白豆蔻中钙的测定条件。通过实验确定了光谱带宽为0.4nm,在单因素实验的基础上,根据Box-Behnken实验设计原理,对影响白豆蔻中钙测定的3个因素进行回归分析,模拟得到预测模型,并确定了最佳测定条件为:硝酸镧的质量浓度为6.23mg/mL、乙炔流量为2073mL/min、燃烧器高度为4.92mm。在此条件下,测定白豆蔻中钙的质量分数为0.165%,与理论预测值基本一致,精密度高,RSD为1.30%,检出限为0.17μg/mL,加标平均回收率为97.5%,相对标准偏差为1.54%。      

响应面法优化连续超临界甲醇制备生物柴油的研究

以大豆油为原料,采用三因素三水平组合设计的响应面法优化了连续反应器中超临界条件下制备生物柴油的工艺条件.研究了反应温度、醇油摩尔比、反应时间以及它们的交互作用对生物柴油产率的影响,并得到了制备生物柴油的最佳反应条件,即反应温度为342℃,醇油摩尔比为15∶1,反应时间为45.4 min,最佳条件下生物柴油的产率高达98.74％.不同原料的反应结果进一步验证了所优化的工艺条件,表明该方法可广泛适用于不同原料.     

响应面法优化板栗面包复合改良剂的研究

利用响应面分析法优化三种面包改良剂在板栗面包中的添加量.以板栗面包评分为评价指标,在考察单因素对板栗面包抗老化效果及面包评分影响的基础上,利用Box-Beheken响应面分析法确定三种改良剂的最佳组合.实验表明:在板栗面包制作过程中按板栗粉及面包粉总质量添加0％α-淀粉酶、1.1％黄原胶、0.3％单甘酯时,板栗面包具有良好的焙烤品质,且在贮存7d后,面包芯硬度比对照组下降46.4％,有效延缓了面包老化,延长了其货架期.     

Optimisation of red pepper seed oil extraction using supercritical CO2 and analysis of the composition by reversed‐phase HPLC‐FLD‐MS/MS

Oil extractions from red pepper seed were performed by supercritical CO₂. Three‐level Box–Behnken factorial design (BBD) from response surface methodology (RSM) was applied to optimise the main extraction conditions including pressure, temperature and concentration of modifier (ethanol). The optimum conditions were as follows: extraction pressure, 27.17 MPa; extraction temperature, 47.67 °C; and the added concentration of modifier, 8.11 vol.%. Under the optimum conditions, the oil yield of 18.4% was obtained, which was well matched with the predicted yield. A simple, stable and sensitive method for the simultaneous determination of saturated and unsaturated free fatty acids in extracted oils using 2‐(11H‐benzo[a]carbazol‐11‐yl)‐ethyl‐4‐methylbenzenesulfonate (BCETS) as labelling reagent with fluorescence detection has been developed. All of free fatty acids (FFA) were found to give a linear response with correlation coefficients of >0.9991. The detection limits at a signal‐to‐noise ratio (S/N) of three are in the range of 19.06–41.19 fmol. This method should have powerful potential for the trace analysis of short‐ and long‐chain FFA from edible oils, foodstuff and other complex samples.     

Apple pomace in gluten‐free formulations: effect on rheology and product quality

The objective of the present work was to formulate a gluten‐free (GF) baked product based on a cassava starch, rice flour and egg white mixture and enriched with apple pomace with minimum processing as source of fibre. Effects of apple pomace and water amount on batters and product quality were analysed by response surface methodology (RSM). Dynamic moduli of batters, specific volume and crumb texture were highly dependent on both apple pomace and water. Higher levels of fibre rendered less cohesive and less resilient crumbs and diminished specific volumes. A suitable balance between amounts of apple pomace and water led to products with enough specific volume and sponginess. Up to 12.5 g apple pomace and water ranging from 115 to 150 g (each 100 g mixture), specific volumes were maintained higher than 2 cm³ g^?1; if apple pomace was increased up to 20 g, water amounts higher than 140 g were necessary to obtain similar results.     

Natural Fiber Improvement by Laccase; Optimization,Characterization and Application in Medium Density Fiberboard

Crystallinity of cellulosic fiber directly affects the physical and chemical behavior of the individual fiber and ultimately the product made from. In a controlled condition, if the natural fiber is exposed to enzymatic hydrolysis, its crystallinity improves without affecting the cellulose component of the fiber. In this work, four basic factors for enzymatic reaction, i.e., temperature, time, pH, and enzyme amount, were optimized using response surface methodology (RSM). The response was taken as the fiber crystallinity index, measured by X-ray diffraction method. The optimum treated fiber was further analyzed for the field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA) and results were compared with untreated fiber. Medium density fiberboards (MDF) were manufactured from optimum treated fiber and its tensile properties and water resistance properties were compared with MDF made from untreated fiber. The observation revealed a maximum of up to 14% increment in fiber crystallinity index (CrI) as compared to untreated fiber. The MDF prepared from optimum treated fiber exhibits improved tensile property and lower water absorption property as compared to MDF prepared from untreated fibers.     

Optimisation of culture conditions and development of a novel fed‐batch strategy for high production of β‐galactosidase by Kluyveromyces lactis

The aim of this study was to enhance β‐galactosidase production by Kluyveromyces lactis CICC1773. Firstly, the optimum culture conditions were obtained by response surface methodology, and the maximum β‐galactosidase activity reached 20.6 U mL^?1, about two‐fold increase than that of the initial conditions (initial fermentation medium and conditions). To further improve β‐galactosidase production, a new fed‐batch strategy based on pH feedback control was developed successfully in a 7‐L fermenter, using 400 g L^?1 lactose as feeding medium. As a result, the β‐galactosidase activity and productivity reached up to 111.61 U mL^?1 and 5.31 U/(mL·h), enhanced by 15.3‐fold and 17.6‐fold superior than the results of initial conditions, respectively. To our knowledge, β‐galactosidase activity obtained was the highest value among the results reported by nonrecombinant strains. These results demonstrated that the new fed‐batch strategy based on optimum culture conditions could be automatic control easily and be conductive to further scale up for industrial fermentation.     

Encapsulationof lycopene from watermelon in calcium‐alginate microparticles using an optimised inverse‐gelation method by response surface methodology

Lycopene exhibits strong antioxidant activity due to its unsaturated molecular bonds, which also contributes to its susceptibility for degradation. Encapsulation techniques can reduce lycopene degradation, increasing its potential applications in functional foods and nutraceuticals. The objective of this study was to optimise the encapsulation of lycopene from watermelon in alginate microparticles using the inverse gelation method. Box–Behnken design was used for the optimisation of three variables: concentrations of alginate (w/v %) and CaCl₂ (g L^?1), and gelation time (min). Two types of alginate were investigated (low viscosity and high viscosity) and optimised separately using encapsulation efficiency and loading capacity as responses. Results indicated that the models had a good fit to the experimental data and the optimal conditions varied depending on the type of alginate. In general, particles prepared with low‐viscosity alginate exhibited higher encapsulation efficiency and loading capacity and could be used for further research.     

Enhancing the levels of 4‐vinylguaiacol and 4‐vinylphenol in pilot‐scale top‐fermented wheat beers by response surface methodology

Top‐fermented wheat beers are desired by consumers because of their distinctive clove‐like and phenolic aroma, in which two characteristic flavour substances, 4‐vinylguaiacol (4VG) and 4‐vinylphenol (4VP), are of vital importance. In this paper, the levels of 4VG and 4VP were the subject of an intensive and detailed investigation. The influence of wheat malt proportion, mashing‐in temperature, boiling time and fermentation temperature on 4VG and 4VP was studied by pilot‐scale brewing experiments using a 10 hL mashing vessel and 20 hL fermentation tanks. Response surface methodology (RSM) was used to explore the possibilities for enhancing the concentration of 4VG and 4VP in top‐fermented wheat beers. Statistical analysis of the results showed that for the ranges of wheat malt proportion studied, mashing‐in temperature, boiling time and fermentation temperature all had a significant influence (p <0.05) on 4VG and 4VP production. Based on the response surface plots, the optimal brewing parameters that maximized 4VG and 4VP levels were as follows: (a) wheat malt proportion 40%; (b) mashing‐in temperature 44°C; (c) boiling time 88 min; and (d) fermentation temperature 19.5°C, resulting in significantly increased levels of 4VG and 4VP (2.418 mg/L and 1.402 mg/L, respectively). These brewing and fermentation parameters were concluded to be the optimal conditions to highlight the typical flavour and aroma of top‐fermented wheat beers. Copyright © 2015 The Institute of Brewing & Distilling     

Production of α‐amylase by Aspergillus oryzae As 3951 in solid state fermentation using spent brewing grains as substrate

BACKGROUND: The optimisation of nutrient levels for the production of α‐amylase by Aspergillus oryzae As 3951 in solid state fermentation (SSF) with spent brewing grains (SBG), an inexpensive substrate and solid support, was carried out using response surface methodology (RSM) based on Plackett–Burman design (PBD) and Box–Behnken design (BBD). RESULTS: In the first optimisation step a PBD was used to evaluate the influences of related factors. Corn steep liquor, CaCl₂ and MgSO₄ were found to be the most compatible supplements to the substrate of SBG and influenced α‐amylase activity positively. In the second step the concentrations of these three nutrients were optimised using a BBD. The final concentrations (g/g dry substrate basis) in the medium optimised with RSM were 1.8% corn steep liquor, 0.22% CaCl₂ and 0.2% MgSO₄ · 7H₂O using SBG as the solid substrate. The average α‐amylase activity reached 6186 U g^?1 dry substrate under the optimised conditions at 30 °C after 96 h. Under the optimised conditions of SSF an approximately 17.5% increase in enzyme yield was observed. CONCLUSION: SBG was found to be a good substrate for the production of α‐amylase by A. oryzae As 3951 under SSF. Copyright © 2007 Society of Chemical Industry