粮食储藏害虫检测方法研究进展

在面粉的各种污染物中,虫卵对面粉的污染最利害,不仅影响面粉及其制品的品质,也影响面粉的出口贸易,因此,研究与开发高效快速检测虫卵的方法十分必要。近年来,针对面粉中虫卵的检测,比较有代表性的方法有染色法、几丁质法、尿酸法、DNA指纹分析技术等;针对面粉中害虫碎片的检测,比较有代表性的方法有浮选法、太赫兹时域光谱等;针对粮食中幼虫的检测,比较有代表性的方法有电导法、近红外光谱法、X射线成像法、图像识别法、声测法等。总结并分析粮食储藏害虫的检测方法,预测其发展趋势,为害虫检测技术的研究提供参考。     

3种染色剂检测大米中米象虫卵感染效果比较

比较了改进后的高锰酸钾、酸性品红、碘 碘化钾溶液处理感染米象虫卵大米的染色效果和检出结果,研究了高锰酸钾对新陈大米卵斑的检测效果。试验结果显示,相对于感染虫卵的大米中幼虫达43.3%的情况,高锰酸钾溶液染色的百粒大米卵斑检出率最大,可达29.0%;新大米感染虫卵的第1天卵斑检出率最高,为26.0%,且不同感染时间的卵斑检出率差异显著;陈大米感染虫卵的第1天卵斑检出率也最高,为22.0%,不同感染时间的卵斑检出率差异不显著。结果表明,采用质量分数为1%的高锰酸钾溶液染色处理大米10 s,可较为快速、准确地检测大米中米象虫卵感染情况;新大米感染虫卵的时间对染色检出卵斑效果有显著影响,而陈大米感染虫卵的时间对染色检出卵斑效果影响不显著。     

3种染色剂检测大米中米象虫卵感染效果比较

比较了改进后的高锰酸钾、酸性品红、碘-碘化钾溶液处理感染米象虫卵大米的染色效果和检出结果,研究了高锰酸钾对新陈大米卵斑的检测效果.试验结果显示,相对于感染虫卵的大米中幼虫达43.3％的情况,高锰酸钾溶液染色的百粒大米卵斑检出率最大,可达29.0％;新大米感染虫卵的第1天卵斑检出率最高,为26.0％,且不同感染时间的卵斑检出率差异显著;陈大米感染虫卵的第1天卵斑检出率也最高,为22.0％,不同感染时间的卵斑检出率差异不显著.结果表明,采用质量分数为1％的高锰酸钾溶液染色处理大米10s,可较为快速、准确地检测大米中米象虫卵感染情况;新大米感染虫卵的时间对染色检出卵斑效果有显著影响,而陈大米感染虫卵的时间对染色检出卵斑效果影响不显著.     

花生壳的改性及其对酸性品红的吸附

研究了花生壳的改性及改性花生壳对酸性品红的吸附。结果表明,花生壳的最佳改性条件为:室温下,花生壳与0.04 mol/L高锰酸钾的固液比为1∶5,改性30 min;改性花生壳的最佳吸附条件为:室温下,于100 m L酸性品红质量浓度为30 mg/L、p H=2的水样中,投加90 mesh筛下改性花生壳0.7 g,吸附60 min。该条件下,酸性品红的脱色率为93.10%,稀释倍数为40倍,低于《污水综合排放标准》(GB 8978-1996)中的一级标准;从实际应用的角度出发,投加量为0.5 g/100 m L时,脱色率达到79.66%,稀释倍数为60倍,达到《污水综合排放标准》(GB 8978-1996)中二级排放标准;改性花生壳对酸性品红的吸附与Freundlich相关方程的拟合程度很高。     

3种HPLC检测器测定单甘酯含量的方法比较

比较高效液相色谱-紫外检测法(HPLC-UV)、高效液相色谱-示差折光检测法(HPLC-RI)、高效液相色谱-蒸发光散射检测法(HPLC-ELSD)测定乳浊液中单甘酯的含量。结果表明：UV法检测单甘酯,杂质干扰严重,样品信号不强,灵敏度低;RI法只有在较高的质量浓度范围内才有较好的线性关系,不适合用于检测较低质量浓度的单甘酯;ELSD法检测单甘酯含量,单甘酯质量浓度在0.040～5.000mg/mL范围内有良好的线性关系,R2为0.9998,样品回收率达到92.94%,相对标准偏差为2.24%,变异系数为2.41%。HPLC-ELSD法灵敏,准确,重复性好,可用于乳浊液中单甘酯含量的测定。     

亚硫酸品红法检测水发食品中甲醛的线性关系

探讨亚硫酸品红法测定水发食品中甲醛含量的线性关系。用亚硫酸品红法检测鱿鱼、虾仁和腐竹中甲醛含量,将试样匀浆,其蒸馏液中有甲醛存在时,亚硫酸根离子与品红生成紫色络合物,显色时间与试液中甲醛含量成反比,由此可定性检测或在一定范围内半定量检测试样中甲醛。待测样液中甲醛含量在1～10μg/mL区间,显色时间在55～13 min之间,且甲醛含量与显色时间有很好的相关性(相关系数r=0.9949),其结果与SC/T 3025-2006推荐的乙酰丙酮法的检测结果在一个数量级内,是一种操作简便、条件要求低、而有参考价值的定性检测法,适合现场定性检测水发食品中甲醛含量及对大批该类样品中甲醛含量的分级检测。     

小麦粉及其制品中偶氮甲酰胺检测方法研究进展

偶氮甲酰胺（azodicarbonamide,ADA）是小麦粉常用的食品添加剂,具有增白、强筋作用。ADA在湿热环境下不稳定,能够转化为联二脲（biurea,BIU）和氨基脲（semicarbazide,SEM）。SEM是兽药呋喃西林的代谢物,具有较强的致癌、致畸、致突变作用。小麦粉及其制品中ADA检测方法可分为直接检测法和间接检测法,直接检测法以ADA为目标检测物,间接检测法以BIU和SEM为目标检测物。本文综述了小麦粉及其制品中ADA检测方法研究进展,分析了我国现行ADA检测标准存在的问题,展望了ADA分析检测研究的发展趋势,为ADA分析检测研究与实践提供参考。     

山野菜营养面条的研制

以小叶芹、刺嫩芽、婆婆丁的汁液为辅料,加到小麦粉中,做成面条,研制出山野菜营养面条。对面条做感官评价,并测定其断条率和吸水率,通过单因素实验和正交实验,确定山野菜营养面条的最佳工艺配方。结果表明:以小麦粉质量为100%,添加小叶芹汁12%、刺嫩芽汁11%、婆婆丁汁6%,制得的面条综合分数最优,感官品质佳,断条率低,吸水率高。     

高效液相色谱法快速测定青海牛羊肉和内脏组分中尿酸和嘌呤

建立青海牛羊肉和内脏组分中尿酸和4种嘌呤(鸟嘌呤、次黄嘌呤、黄嘌呤和腺嘌呤)的2种分析方法,一种是采用高效液相色谱(high performance liquid chromatography,HPLC)法同时测定上述5种组分,并折算出尿酸总含量;另一种是采用生物酶解法将嘌呤全部转化后,采用HPLC法快速测定其降解产物尿酸。2种方法均采用Agilent Zor Bax Eclipse XDB-C18色谱柱分离,浓度为7×10~(-3) mol/L的KH_2PO_4-H_3PO_4(pH=3.83)溶液作为流动相,紫外检测波长为254 nm。结果表明:同时测定法中,被测物质在上述条件下分离良好,在较宽的浓度范围内线性良好,相关系数(r)均在0.998 4以上,平均回收率为92.2%~119.8%,相对标准偏差(relative standard deviation,RSD)为0.78%~10.43%;转化后尿酸快速测定法中,被测物质在1~70 mg/L质量浓度范围内与峰面积间的线性关系良好,r=0.999 4。将2种分析方法得出的总尿酸含量进行比较,经配对t检验,结果无显著性差异(P=0.7730.05)。2种方法均可用于牛羊肉和内脏组分中嘌呤类物质的检测。     

利用DNA分子指纹图谱技术检测小麦粉中害虫的研究

为开发快速检测我国成品粮中害虫的技术,研究了DNA分子指纹图谱技术检测小麦粉中主要害虫的碎片和虫卵的含量。结果表明,通过对害虫的延长因子EF1基因片段引物的筛选和PCR条件的选择,确定了有效地检测出来小麦粉中的赤拟谷盗、杂拟谷盗和锯谷盗的成虫碎片、幼虫和卵通用引物和PCR扩增条件。通过改良的PCR技术可在4 h内快速检测杂拟谷盗、锯谷盗的卵、幼虫和成虫碎片。最低检出限为可检测出小麦粉中0. 05%(m/m)卵和幼虫、1%成虫的碎片,灵敏度超过了国际标准。DNA指纹图谱中电泳条带亮度(Y)与被检测的不同害虫碎片含量(X)成正相关,回归方程为Y=858. 36X+74. 540相关系数R为0.961 9。利用该技术检测随机取样的小麦粉中成虫的碎片,检测的准确率最高可达80. 56%。结果说明了利用DNA分子指纹图谱技术可快速检测出小麦粉中害虫的碎片、幼虫和卵含量,并可预测小麦粉中害虫的感染程度。本研究为开发快速小麦粉中害虫的快速检测技术具有重要的参考意义。     

Detection of eggs of stored-product insects in flour with staining techniques

Chemical stains were investigated with the aim of developing a method for detecting eggs of stored-product insects in refined wheat flour (white flour), so that eggs and flour particles could be distinguished easily. Eggs of the rust-red flour beetle, Tribolium castaneum, the saw-toothed grain beetle, Oryzaephilus surinamensis and the rice moth, Corcyra cephalonica were detected by staining with 0.1% bromocresol green or 1:1 mixture of bromocresol green+0.5% orange G solution after acid digestion of the flour particles. In contrast to the standard AACC method of staining with iodine solution where both eggs and flour particles were stained brownish-yellow or yellow, bromocresol green alone or in mixture with orange G, differentially stained the insect eggs and the flour particles distinct orange and green, respectively. Eggs in flour could also be detected using 0.05% acid fuchsin but both eggs and flour particles were stained uniformly pink.     

Influence of malathion resistance status on survival and growth of Tribolium castaneum (Coleoptera: Tenebrionidae), when fed on flour from insect-resistant and susceptible grain rice cultivars

The effect of insecticide resistance on the potential for control of stored product insect pests based on plant resistance was evaluated. Flours made from three rice cultivars (cvs.) that showed resistance or susceptibility to feeding by Tribolium castaneum were studied, using two strains, resistant and susceptible to the organophosphate insecticide, malathion. Flours made from rough, brown and milled rice were used to help identify the locus of any cultivar resistance mechanisms. The insect-resistant (Dawn) and moderately resistant (Lebonnet) cvs. had fewer eggs laid and caused greater mortality of the insects than the susceptible cultivar (cv.) (IR8). For all cvs., flour from brown rice was the most suitable for insect survival, whereas the highest larval weights were found in milled and the lowest in rough rice flours. On the other hand, the highest mortality of the susceptible strain occurred in milled rice flours. The larvae resistant to malathion survived significantly better than those of the susceptible strain, when fed on flour from the insect-resistant cv. (Dawn). The cause of this positive interaction between the insecticide resistance status of T. castaneum and the grain resistance is not known. The mechanism of malathion resistance occurring in this strain is enhanced malathion-specific carboxylesterase activity but it is not known how this can confer survival benefits, when the insect feeds on flour from the resistant cv. These results could have practical implications for the efficacy of stored product pest control using varietal resistance in situations where insecticide resistance is prevalent.     

Alkali Gelatinization of Flours

Flours from 12 different species of grain, pod seed, and tuber plants were gelatinized with aqueous sodium hydroxide at room temperature. Changes in physical appearances and viscosity patterns were noted over a 7-day quiescent period in graded-strength alkali solutions in sealed jars. The alkali strength, 0.07–0.85-N , was sufficient to peptize proteins and hemicelluloses. Color development was strong and rapid and several flours evolved notable amounts of ammonia and perhaps amines. No two flours produced the same viscosity development patterns as time progressed. From the observed visual and viscosity changes, it was apparent that alkali gelatinization of the flours generally was complete within several hours at levels of 2.82-3.52 meq NaOH/g flour. Some discussion centers on differences between flours, between some species of flours and the starches obtained from those species, and the possible role of other flour constituents on the gelatinization behavior.     

Detection of insect fragments in wheat flour by near-infrared spectroscopy

Insect fragments in commercial wheat flour are a major concern to the milling industry because consumers expect high quality and wholesome products at the retail level. Thus, the US Food and Drug Administration (FDA) has established a defect action level of 75 insect fragments per 50 g of flour. Millers routinely test their wheat flour to comply with this federal requirement and to deliver sound flour to their consumers. The current standard flotation method for detecting fragments in flour is expensive and labor intensive. Therefore, we examined the possible use of a rapid, near-infrared spectroscopy (NIRS) method for detecting insect fragments in wheat flour. We also compared the sensitivity and accuracy of the NIRS method with that of the current standard flotation method. Fragment counts with both techniques were significantly correlated with the actual number of fragments present in flour samples. However, the flotation method was more sensitive than the NIRS method with fragment counts below the FDA defect action level. We were unable to predict whether the number of fragments in a sample exceeded the FDA action level with our NIRS instrumentation. However, we were able to predict accurately whether flour samples contained less than or more than 130 fragments. Although current NIRS instruments are unable to detect insect fragments at the FDA action level, this method should be re-examined in the future because NIRS technology is rapidly improving.     

Comparison of properties of native and extruded amaranth (Amaranthus cruentus L. - BRS Alegria) flour

The aim of this study was to compare some of the properties of native and extruded amaranth flour obtained under mild and severe extrusion conditions. The chemical composition of the flours was similar. Flours obtained by both extrusion processes presented high solubility in water, low values of L∗ (luminosity) and an absence of endothermic peak on the DSC method. Water absorption, retrogradation tendency, final viscosity and the viscous behavior by rheology analysis were also studied. The results indicate that extruded flours have a good potential as an ingredient for food exposed to heat treatment at a high temperature and mechanical shear, for use in instant meal products. On the other hand, original flour properties are comparable to those of amaranth starch, which exhibits similarly high quality paste stability, low solubility in water, and elastic behavior, and could be used as a substitute for raw flour in a range of food formulas.     

Effect of cold plasma on insect infestation and keeping quality of stored wheat flour

Cold plasma has been applied as an alternative technology for pest control of stored commodities. Wheat flour is infested with three different insect species and subjected to plasma treatment at two power levels (40 W and 60 W) with three-time intervals. Further, the growth of larvae and pupae of insects was examined at different storage periods by sieving and visual inspection methods. There was a significant increase in the death of larvae and pupae of insects. Iodine and bromocresol green staining tests were used to detect the eggs in the flour. The parameters related to the quality of flour during the storage, like lipase enzyme activity and oxidation of fats, were analyzed. A decrease in lipase enzyme activity by 35% on the 90th days was observed in 60 W-30 min treated samples. The reduction in lipase enzyme activity resulted in a lower Thiobarbituric acid value. No significant change was observed in the color profile of wheat flour after the plasma treatment. This study shows that cold plasma can be applied as a novel technology for pest control management to enhance stored food product quality.     

The efficacy of sieving, filth flotation and Tullgren heat extraction for detecting various developmental stages of Tribolium castaneum and Ephestia kuehniella in samples of wheat grain, flour and semolina

A prerequisite for effective pest risk management in food is the unbiased interpretation of results obtained by various detection methods. In this study we compared the sensitivity of filth flotation tests, sieving and heat extraction in Tullgren–Berlese funnels for detecting insect contaminants. Samples of wheat grain, flour and semolina were contaminated with eggs, juveniles and adults of Tribolium castaneum, and eggs or larvae of Ephestia kuehniella. Calibration methods were applied for every detection method, and total and sample recoveries and detection limits were calculated for each method, food substrate and contaminant type. The tested contaminants were not detected on a qualitative level by any single technique, instead a combination of techniques was necessary for detection. Sieving was the method with the highest total recoveries, ranging from 90 to 100%. Filth flotation was a uniquely effective for egg detection, with total recoveries ranging from 65 to 95%. The extraction of adults and larvae of both species in Tullgren–Berlese funnels failed in semolina and flour, and was of very limited success in grain. The detection limits for sieving were from 1 to 16 contaminants/kg commodity. The detection limits for filth flotation were from 224 to 508 eggs, and 58 to 507 adults or larvae/kg commodity. The sample recoveries were usually influenced by sample size, species, stadium and their interactions, and indicated how to optimize method protocols. The calibration of methods provided estimates of contaminant densities different from those obtained without calibration. Our work revealed that some currently used methods are not sensitive enough to detect all stages of insect pests, or in some cases, low levels of pest infestation. This lack of sensitivity potentially enables the infested cereal food product to continue down the food processing chain even after laboratory inspection.     

An overview of near-infrared spectroscopy (NIRS) for the detection of insect pests in stored grains

Applications of near-infrared spectroscopy for measuring various aspects of grain quality have expanded rapidly in recent years. One application that could be of particular use to growers and industry is the detection of insect pests across a range of stored grains. This prospect was first reported over 20 years ago, but the accuracy of this technique does not currently meet FDA standards for the quantification of insect fragments in bulk wheat and flour samples. When considering bulk samples, near-infrared spectroscopy may be suitable for identifying the presence of infestation in samples, followed by flotation testing to provide an accurate quantitative value. Much higher accuracy has been found for the detection of pest species at the single-kernel level. With faster spectrophotometers and kernel sorting systems, single-kernel analysis is likely to be utilised more in the future and could even render bulk analysis of samples redundant. This technology could allow for the detection and identification of pest species in every single kernel of a representative grain sample. The development and application of more sensitive spectrophotometers, such as FT-NIR (Fourier transform near infrared) and more powerful chemometric data analysis techniques are also likely to provide significant improvements, through allowing the minute chemical differences present in bulk infested grains to be accurately detected and quantified.     

Rheological and functional properties of flours from banana pulp and peel

Unripe banana flour can be an alternative to minimize post‐harvest loss and to increase the aggregate value of banana fruit. Flour from unripe banana is rich in phytosterols and resistant starch, being proposed as health food. Flours from unripe banana peel and pulp were evaluated on their composition, phytosterols content, thermal and rheological properties, and pasting profiles. High amounts of β‐sitosterol, campesterol, and stigmasterol were found in flour from banana peel. These samples showed lower viscosity values of pasting profiles, lower energy enthalpy on gelatinization, and higher temperature of gelatinization than those ones from pulp. Anti‐oxidant treatment of fruits with citric acid does not change pasting profiles of flours from pulp, but resulted in slight increase in viscosity, suggesting that structure of starch could be modified by acidification.     

Incorporation of pulse flours of different particle size in relation to pita bread quality

BACKGROUND: To increase pulse consumption, pita bread was fortified with pulse flours milled from green lentils, navy beans and pinto beans, which were ground to produce fine and coarse flours. Pita breads were prepared using composite flours containing pulse flours (25, 50, 75%) and wheat flour or 100% pulse flours and adjusting the amount of water required for mixing based on farinograph water absorption. Pita bread quality was evaluated according to diameter, pocket height, specific loaf volume, texture and crust colour. RESULTS: Blends made from pulse flours with coarse particle size showed higher rates of water absorption. All composite flours and 100% pulse flours produced pitas with pockets, confirming their suitability for this product. Crust colour of pitas was affected less by navy bean flour than by lentil flour. Pita breads made with pinto bean flour were superior in texture. Overall, navy and pinto bean flours appeared more suitable for pita bread. Flours with coarse particle sizes produced pitas with better colour and texture. Sensory parameters of pitas containing 25% coarse pinto or navy bean flour were as good as or better than those from the wheat control. CONCLUSION: Acceptable pita breads can be made using pulse flours, although the substitution level is limited to 25%. Copyright © 2012 Society of Chemical Industry