Determination of moisture in white flour,ground wheat and whole wheat by near infrared reflectance using a single calibration

A single calibration for the determination of moisture in white flour, ground wheat and whole wheat by near infrared (n.i.r.) reflectance analysis is presented. The predictive accuracy of the calibration compared with moisture determined by oven drying on 68 samples was 0.22%.     

Application of response surface methodology for the optimization of oxidants in wheat flour

The objective of this study was to apply the statistical technique known as response surface methodology (RSM) to optimize the proportion between three oxidant compounds compromising lipoxygenase enzymes (x₁), benzoyl peroxide (x₂) and ascorbic acid (x₃) on wheat flour colour and some rheological characteristics of the dough. P, L and W parameters were obtained using a “Chopin” alveograph. Flour colour, characterized by brightness (Lc) and hue (b), was measured using a HunterLab colorimeter and was ranked visually by selected judges. Three regression models were fitted to the dependent variables P, L and Lc and showed non-significant lack of fit (p > 0.114) with an elevated determination coefficient (0.92, 0.84 and 0.94, respectively). A mixture containing 0.27% of x₁, 4.80 ppm of x₂ and 325 ppm of x₃ was obtained from the regression optimization and used for validating the models. These results suggest that, instead of the empirical methods, RSM can be applied to determine the optimal proportion between oxidant compounds normally used to improve colour and rheological parameters in wheat flour.     

Collaborative evaluation of near infrared reflectance analysis for the determination of protein,moisture and hardness in wheat

Different methods for the calibration of near infrared reflectance (n.i.r.) instruments for determination of protein, moisture and kernel hardness in wheat by using 11 instruments of the same model series, were collaboratively assessed. The use of the same calibration constants (other than the bias or intercept constant which must be set separately for each instrument) resulted in significantly better reproducibility in the determination of protein in ground wheat than the use of constants determined separately for each instrument. In the case of accuracy against the reference Kjeldahl method the results using universal constants were not significantly different compared with those using constants individually determined by each laboratory for its own instrument. The use of different grinders of the same type resulted in between-grinder biases in some cases but not in worse reproducibility or accuracy than using one grinder. Therefore, using a common calibration and grinder brings the different laboratories' n.i.r. protein results closer to each other but not necessarily closer to Kjeldahl results. In any case, the agreement of the protein results from one instrument to another or between n.i.r. and Kjeldahl should be within about ±0.50% if the instruments are correctly adjusted. Wheat moisture was measured using unground samples and the same constants (other than the bias) for each instrument when the reproducibility was 0.20% and average accuracy against oven drying was 0.39%. Individual calibrations were not attempted. Wheat kernel hardness, classified as ‘hard’ or ‘soft’, was assessed by eight laboratories on 20 samples using different models of grinder and different constants. Six laboratories achieved a near perfect classification with only three errors in all, but the other two had seven errors between them.     

A rapid method for the determination of pentosans in wheat flour

A rapid and reproducible method is presented for the determination of pentosans in wheat flour.Flour (approximately 5 mg) is added to 2ml of water followed by 10ml of a solution of glacial acetic acid, hydrochloric acid, phloroglucinol and glucose in a stoppered boiling tube.The boiling tube is placed in a water bath for twenty-five minutes and the absorbance of the resulting solution measured at 552nm and 510nm.The absorbance of interfering sugars differs very little at these two wavelengths but is considerable for the pentosans. Accordingly, the pentosans may be estimated, even when an excess of interfering sugars is present, by subtracting the absorbance at 510nm from that at 552nm.     

微波测定小麦水分的研究

对不同功率、微波时间和样品量与小麦水分的关系进行了分析,找出微波测定小麦水分最优条件出现的范围。并以此为基础,根据Box-Behnken试验设计原理,采用3因素3水平响应面分析方法,建立多项式回归方程的预测模型,确定微波测定小麦水分的最优条件。试验表明,最优条件为微波功率680W,微波时间10.8min,样品量2.63g,此时测定的小麦水分为11.52%,与GB/T 5497—1985测定结果相近。     

面粉中戊聚糖含量测定方法的探讨

对测定面粉中戊聚糖含量的地衣酚 -盐酸法进行了研究 ,得到如下结论 :面粉中存在的己糖干扰可通过双波长 (670、580 nm)下吸光度的差值消除 ;利用酵母发酵去除葡萄糖会带来更多干扰 ;对地衣酚 -盐酸法和间苯三酚法进行了比较 ,二者所得可溶性戊聚糖含量相似 ,但后种方法测得总戊聚糖含量略低。     

面粉白度优化研究进展

面粉白度是评价面粉质量重要指标,也是影响面制食品感官品质重要因素。该文从原粮品质、制粉工艺和色泽改良剂三个方面对影响面粉白度因素进行分析,并总结改善面粉白度具体方法,为提高面粉白度提供科学依据。     

面制品中溴酸钾残留量的测定方法

针对当前市场销售的面粉、面包粉、面包等面制品中存在的不遵循国家标准添加溴酸钾的现象,综述了目前国内外可用于溴酸钾残留量检测的分析方法,以求在食品生产和流通环节中加强监督管理,保障面制品的食用安全.     

高效液相色谱-紫外检测法快速测定小麦面粉中偶氮甲酰胺

建立小麦粉中偶氮甲酰胺的高效液相色谱快速检测法。方法 样品经二甲亚砜-丙酮混合溶剂超声振荡提取,采用Hypersil-C₁₈色谱柱(250 mm×4.6 mm,5 μm),流动相为10 mmol/L H₂SO₄水溶液,流速为1 ml/min,检测波长为275 nm,进样量20 μl,二极管阵列检测器定量。结果 偶氮甲酰胺在0.01～1.00 mg/ml范围内呈良好线性关系,相关系数r=0.999 2,RSD<4.3%,平均回收率为95.9%;山东地区85份样品偶氮甲酰胺含量检测结果均小于检出限,符合现行限量标准。结论 本方法准确可靠,方便快捷,灵敏度高,适合于大批量小麦粉中偶氮甲酰胺的检测。     

气相色谱法测定小麦粉中过氧化苯甲酰探讨

介绍了小麦粉中过氧化苯甲酰含量的气相色谱测定法,讨论了测定中的注意事项。     

小麦粉中溴酸钾含量快速测定方法研究

根据溴酸钾(KBrO3)可在酸性条件下氧化3,3',5,5'-四甲基联苯胺(TMB)而显色的原理,建立了小麦粉中溴酸钾定性检测的目视比色法和定量检测的分光光度法。研究了体系酸度、显色液用量、反应时间对显色的影响,并确立了最优化的实验条件。结果表明:在最优化实验条件下,显色体系的颜色随溴酸钾含量的升高而逐渐加深,溴酸钾浓度在0~4 mg/L范围内符合比尔定律,线性回归方程为ΔA=0.2437C-0.005 2,R2=0.999 3。可用于实际样品的测定,目视比色法可快速确定溴酸钾的含量范围,分光光度法的回收率为96.51%~101.70%,RSD为1.79%~3.12%,能够满足市场监管的需求。     

小麦粉自由巯基(-SH)测定方法的对比研究

小麦粉自由巯基的含量直接影响小麦粉的加工品质,从而影响小麦粉的用途。对比研究了3种自由巯基检测方法在巯基的提取、显色反应等方面的优劣,并分别以低筋粉、中筋粉和高筋粉面粉加工厂原粉及市售饺子粉(低筋粉)、标准粉(中筋粉)和面包粉(高筋粉)为原料,并分析了几种方法对不同原料的检测适用性。结果表明:从加标回收率的角度看,方法一、方法二均可用于市售低筋粉和中筋粉的自由巯基含量的检测,几种方法均不适于测定市售高筋粉的巯基含量;3种方法均可用于小麦原粉巯基含量的检测。总体来讲,方法一是适用性和方便性最佳的检测小麦粉自由巯基的方法。     

小麦粉加工精度结果判定的探讨

以库存检查收集到的小麦制成的小麦粉为研究对象,统计分析小麦粉粉色、麸星对照实物标准样品的分等情况,进一步研究小麦粉等级判别、加工精度同粉色、出粉率的关系。结果表明:241份小麦的平均出粉率61.4%,最大值68.9%,最小值50.1%;平均白度值为76.9。出粉率与白度值不完全呈负相关关系,说明粉色与小麦品种有较大关系。     

奇亚籽水分、脂肪、蛋白质和灰分的近红外 光谱快速检测模型优化

水分、脂肪、蛋白质、灰分是重要的奇亚籽品质指标,目前主要依赖于化学法测定,过程烦琐,耗时费力,且不能多指标同时监测。以103份不同产地的奇亚籽为建模样本,通过19种光谱预处理方法和最佳谱区范围的筛选分别建立了奇亚籽中水分、脂肪、蛋白质、灰分的偏最小二乘模型。结果表明:对于水分采用Savitzky-Golay滤波平滑(SG)对光谱进行预处理,脂肪采用一阶导数(1st)和多元散射校正(MSC),蛋白质采用1st、标准正态变化(SNV)和SG,对于灰分采用1st、SNV和Norris微分平滑(ND)组合光谱进行预处理,针对各参数最佳预处理光谱采用人工法进行谱区筛选建立模型,得到水分、脂肪、蛋白质和灰分的验证集相关系数分别为0. 993、0. 972、0. 925和0. 923。结果显示,利用近红外光谱可以实现对奇亚籽的水分、脂肪、蛋白质以及灰分的同时快速无损检测,在大规模奇亚籽原料的分选中提高检测效率。     

紫外二阶导数光度法测定小麦粉中过氧化苯甲酰的研究

研究了紫外二阶导数分光光度法快速测定小麦粉中过氧化苯甲酰的方法，同时对样品提取和基体干扰进行了研究。回收率为95％-110％，最低检出限1．0μg/ml。该方法准确可靠，成本低，检测快速。     

Possibilities of using near infrared reflectance/transmittance spectroscopy for determination of polymeric protein in wheat

Possibilities of using near‐infrared reflectance and near‐infrared transmittance (NIR/NIT) spectroscopic techniques for detecting differences in amount and size distribution of polymeric proteins in wheat were investigated. To evaluate whether differences in polymeric protein due to genetic or environmental variations were detectable by NIR/NIT techniques, wheat materials of different background were used. Size‐exclusion high‐performance liquid chromatography was applied to detect variation in polymeric protein. Partial least squares regression gave high R² values between many protein parameters and NIR/NIT spectra (particularly second‐derivative spectra of NIR 1100–2500 nm region) of flours, while no such relationship was found for whole wheat grains. Most and highest correlations were found for total amount of extractable and unextractable proteins and monomer/polymer protein ratio. Some positive relationships were found between percentage of total unextractable polymeric protein in the total polymeric protein and percentage of large unextractable polymeric protein in the total large polymeric protein and NIR/NIT spectra. Thus, it was possible to detect differences in polymeric proteins with NIR/NIT techniques. The highest amount of positive correlations between NIR/NIT spectra and protein parameters was found to be due to environmental influences. Some correlations were found for breeding lines with a broad variation in gluten strength and polymeric protein composition, while a more homogeneous sample showed less correlation. Thereby, detection of variation in amount and size distribution of polymeric protein due to cultivar differences with NIR/NIT methods might be difficult. Copyright © 2007 Society of Chemical Industry     

谷氨酰胺转胺酶在面制品中的应用

简要回顾谷氨酰胺转胺酶的发展历史,描述其理化性质和作用机理。详细阐述谷氨酰胺转胺酶在面条、烘焙食品等面制品中的应用,并展望其在食品中广阔的应用前景。