不同烘干试样方法测定粮食、油料水分含量结果对比试验探讨

针对在GB/T 5497-1985中,105℃恒质法烘干试样步骤中,试样复烘至恒质的操作过程繁琐、费时,影响测定结果因素颇多,容易出现试验误差等问题,探究提出了3.5h(油料120min)1次烘干的改进方法。采用105℃恒质法和改进法分别测定了小麦、小麦粉、大米及大豆4个品种共32个样品的水分含量进行对比试验,结果表明:使用改进法测定的水分含量结果与105℃恒质法测定的水分含量结果的差值≤0.2%,符合GB/T 5497-1985规定的方法允许差≤0.5%的要求。用其测定粮食、油料水分含量是有效可行的。     

微波辅助提取—高效液相—电感耦合等离子体质谱法测定生米与熟米中各形态砷的含量

建立微波辅助提取—高效液相—电感耦合等离子体质谱(MAE—HPLC—ICP—MS)测定大米中各种形态砷含量的方法。通过对微波温度、时间、功率进行条件优化,在80℃、600 W、20min的微波条件下可得到最佳提取效果。As(Ⅲ)、DMA、MMA、As(Ⅴ)4种砷形态的标准曲线线性良好,样品加标回收率在86.15%~109.80%。所建方法与GB/T 5009.11—2014比较发现:两种方法测得的As(Ⅲ)、DMA、As(Ⅴ)含量无显著差异,而所建方法测得的MMA含量则高于GB/T 5009.11—2014的。根据所建方法分别测定生米和熟米中各种形态砷的含量,发现大米经过蒸煮后As(Ⅲ)和DMA比重下降,而MMA和As(Ⅴ)比重上升,总砷浓度下降了8.77%。     

影响红外水分仪测定粮食水分的因素

采用GB/T 5497—1985和红外水分快速测定仪分别对粮食样品水分进行了测定,结果表明红外干燥法大大地缩短了检测时间,且操作简便迅速,测量结果可靠,可以适应快速检验的要求。     

不同标准测定粮食水分的对比试验

研究旨在进一步提升粮食水分测定工作效率。针对粮食水分进行测定时，主要选用了对比试验的方式展开。为了确保测定结果的准确性，主要结合GB5497-1985《粮食、油料检验水分测定法》关于定温定时测定方法的标准方法处理，在130℃±2℃（40min）标准下去测定粮食水分数值。同时，还使用GB5009.3-2016《食品安全国家标准食品内水分的测定》关于第一法直接干燥标准方法应用下，得出测定出来的粮食水分数值。结果显示：针对两个不同标准方法下所测定得出的粮食水分差异，发现两个结果之间的差异并不明显，说明两种测定方法测定结果趋于一致。因此，为更好地提升粮食水分测定相关工作效率，在条件一致的情况下，可以重点选用130℃定温定时标准方法完成对比试验工作，且此种测定方法值得推广。     

水浸悬浮法测定玉米水分的研究

常规玉米水分主要依据GB5009.3规定的直接干燥法进行测定,高水分玉米的水分测定一般采用两次烘干法(GB/T20264—2006)。这两种方法皆耗时长,与之相比,用水浸悬浮法测定玉米水分更简便、快速。通过F检验法可知,水浸悬浮法与直接干燥法测定干玉米水分时,两种方法的精密度不一致;水浸悬浮法与两次烘干法测定湿玉米水分时,两种方法的精密度一致。由此可见,水浸悬浮法在测定高水分玉米的水分时优势更为显著。     

快速检测木质活性炭碘吸附值方法研究

碘吸附值是衡量活性炭质量优劣的重要指标,该实验以GB/T 12496.8—2015中（150±5） ℃烘箱法为参考,用卤素水分测定仪HX204确定木质活性炭快速检测方法主参数为温度130 ℃,加热模式标准,关机模式1 mg/32 s。用卤素水分测定仪测定的水分计算干基碘吸附值,与烘箱法测定的碘吸附值相对标准偏差为1.36%,在误差允许范围,两种方法碘吸附值无显著差异。     

用红外水分测定仪快速测定食品中的水分

本文采用GB/T5009.3-2003和红外干燥法对三种固体食品样品分别进行了水分检测。结果表明红外干燥法大大缩短了检测时间,且操作简便迅速。经过显著性检验,红外法检测结果与国标中(105±2)℃,(3+1)h的直接干燥法无显著性差异。     

大米中直链淀粉含量快速测定方法的探讨

建立一种快速、准确的测定大米中直链淀粉含量的方法.在GB/T 15683-2008方法的基础上,脱脂后样品与标准品,采用130℃恒温干燥3 h的水分校准法制备试样,再经碱液分散后与碘试剂呈显色反应,于720 nm处测吸光度.该方法显色液的吸光度值与直链淀粉含量具有良好的线性关系,相关系数R2为0.999 9,相对标准偏差小于2.0%,具有良好的稳定性,并可节省检测时间40 h.与国标水分平衡法制备样品测得的结果对比分析,水分校准法具有分析速度快、准确度高、重现性好等特点,适于大批量大米直链淀粉含量分析检测.     

兴化脱水香葱产品水分测定方法的探讨

以江苏兴化香葱的冷冻干燥产品(FD葱)和热风干燥产品(AD葱)为实验材料,按GB/T 5009.3-2003这<食品中水分的测定>中规定的方法,并参考中国药典附录中的相关规定,分别采用直接干燥法、减压干燥法、蒸馏法测定了样品的水分含量,同时测定了样品在105℃烘干前后的紫外光谱以及还原糖和总糖含量.结果表明:样品经105℃烘干后,还原糖及总糖含量均有所下降,紫外光谱亦发生明显变化,这表明样品的化学成分已有所改变,部分分子发生了脱水反应,导致分析结果偏高,而减压干燥前后样品外观和气味均未见明显改变.实验结果表明,对于高温干燥时容易发生焦化的某些果蔬产品,其水分测定应以减压干燥法为宜.     

美国蛋制品检验法及规格

总固体或水分 方法 方法的基础 参阅 (a)真空烘箱,法(法定) 水分在100℃和71—74厘米,真空干燥5小时除去。 AOAC 11版(1970),IAPI (b)普通烘箱法 液体的和解冻样品的水分在105—107℃过夜除去。干样品的水分烘1.75小时除去之。 IAPI(1968)     

A comparative evaluation of methodologies for water content determination in green coffee

The main objective of this study was to compare methods for mass loss evaluation in green coffee to water content determination by Karl Fischer titration (KFT). The following methodologies were tested: (i) ISO 6673 (oven drying at 105 °C for 16 h); (ii) the reference method employed by the Brazilian Agriculture Ministry (oven drying at 105 °C for 24 h)—BRAMw, employing whole beans and BRAMg, employing ground beans; and (iii) infrared drying (IRD). Reference oven drying methodologies ISO 6673 and BRAMw presented results statistically equivalent (p>0.05) to those from KFT in the moisture content range that is of interest for green coffee commercialization (8-13 g/100 g), whereas IRD results were lower than those for KFT. ISO 6673 and BRAMw also presented the highest values of correlation coefficients to KFT. Differences in moisture content determination became more significant for lower moisture content values (4-7 g/100 g), probably due to loss of organic volatile substances during drying and occurrence of moisture loss during sample grinding.     

Evaluation of Air Oven Moisture Content Determination Procedures for Pearl Millet (Pennisetum glaucum L.)

This study evaluated moisture content determination procedures for pearl millet using seven different air oven methods. The moisture content of the pearl millet samples varied from 11–41% (wet basis). The procedures included 130°C for 1 h; 130°C for 2 h; 105°C for 5 h; 105°C for 48 h; 105°C for 72 h; 130°C for 16 h; and 130°C for 20 h. Analysis of variance revealed that at high moisture content levels above 27% (wet basis), and the mean values of the moisture content determined were not significantly different (p > 0.05). Error analysis carried out showed that the moisture content determination methods were adequate to completely remove the moisture in pearl millet with moisture less than 35% (wet basis). Regression models were developed to predict the base moisture determination method (105°C for 72 h) as a function of other procedures.     

Determination of moisture and oil in the seed of winter rape (Brassica napus): I.-Comparison of oven methods for the determination of moisture

The method for estimating moisture in winter rape seed (Brassica napus) by drying at 130° for 1 h gives results significantly higher than methods of drying at 103° and 105°. For the routine estimation of moisture in large numbers of samples a convenient method is to dry 10 g of whole seed for 16 h. This method compares favourably with results obtained on milled samples dried at 103° for 5 h or 105° for 16 h.     

DETERMINATION OF THE MOISTURE CONTENT OF BARLEY

The method of the International Organization for Standardization, (ISO 712–1985) for the determination of moisture in cereals and cereal products, has been tested by members of the Analysis Committee of the European Brewery Convention on samples of barley. The method, which relies on loss in mass on drying at 130–133°C for 2 h, is recommended for use as a replacement for the current method, based on loss in mass on drying at 105–107°C for 3 h. It was judged that precision values were independent of concentration over the range 11 to 13% m/m. Repeatability (r₉₅) and Reproducibility R₉₅) values of 0.13 and 0.55 respectively were obtained over this range. At a mean level of 21.7% m/m, the r₉₅ and R₉₅ values were 0.27 and 2.6 respectively. This was probably due to errors associated with the double drying technique which is necessary for samples at this moisture content.     

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。     

两种干燥方式对鸡油菌氨基酸组成及评价的影响

为探究烘干（干燥箱60℃ 16 h）、自然晾干（在室温（25±2）℃、湿度38%±1%、东南三级风、晒干5 d）两种干燥方式对西藏林芝野生鸡油菌样品19种氨基酸的组成及评价的影响。采用2,4-二硝基氟苯衍生高效液相法检测18种氨基酸,色氨酸检测采用比色法。结果表明,林芝鸡油菌的蛋白质较为丰富,烘干（22.52%）较自然晾干（31.13%）有损失;必需氨基酸占总氨基酸的比值（自然晾干28.27%、烘干28.10%）低于理想蛋白模式;有较高的鲜味氨基酸（F/T为自然晾干37.38%、烘干32.02%）和药用氨基酸（D/T为自然晾干57.01%、烘干54.78%）;谷氨酸、天冬氨酸、精氨酸、丝氨酸、丙氨酸含量相对较高,烘干较自然晾干有减少;从3种氨基酸评价模式（WHO/FAO氨基酸模式成人需要量、11~18岁需要量和鸡蛋白）看,两种样品的第一限制性氨基酸均为赖氨酸,烘干样品的化学评分（CS）和氨基酸评分（AAS）均高于自然晾干样品,含硫氨基酸（蛋氨酸＋半胱氨酸）的评分最高,两份样品EAAI均低于鸡蛋白模式。可采用烘干方式干燥鸡油菌以提高干燥效率。     

Comparison of various methods for determination of water in white yoghurts

Water content was determined in 11 samples of white yoghurts. Several techniques, namely Karl Fischer (KF) volumetric titration, near and middle infrared spectroscopy (MIR), oven drying and moisture analyser were used. Optimisations of solvent, titration temperature and extraction time were carried out for the KF titration. Methanol at room temperature with 5 min extraction period was used as final conditions. For the infrared spectroscopy (FTIR) the suitable solvent and the appropriate wavenumbers for water analysis were chosen. The measurement in the near infrared (NIR) region at the wavenumber 10270 cm⁻¹ using acetonitrile as solvent and transmission method was evaluated as the best of the FTIR methods. Based on the comparison of individual methods the oven drying at 105 °C seems to be the most suitable, but it is the most time consuming. However, KF volumetric titration and especially FTIR methods appear to be good alternatives to the drying methods.     

固定床热风干燥模式对荔枝干制特性的影响

采用固定物料位置固定热端(模式I)、变换物料位置固定热端(模式II)和固定物料位置变换热端(模式III)三种模式对荔枝果实进行固定床热风多阶段干燥,分别测定了不同物料层(A、B和C三层)物料的热风风速、温度、水分含量、干燥速率、有效扩散系数(Deff)和体积收缩率。结果表明,不同的干燥层物料的热风和温度分布不均匀。经过四阶段共26 h干燥,模式I、II和III中整体样品的水分含量分别为45.70%、42.07%和41.18%。模式I中A层物料的终水分含量为28.44%,显著低于B层和C层样品(p<0.05),Deff为1.48×10-6m2/s,显著大于B层和C层物料(p<0.05)。模式II各层间物料终水分含量和Deff差异不显著(p>0.05),干燥较均匀。模式III中A层物料的终湿基含水量和Deff与B、C层的物料的相比差异不显著(p>0.05),干燥较均匀,可实现简约操作和规模加工。