基于电子鼻与气相色谱-质谱法探究小麦与碎麦挥发性香气成分差异

目的 解析小麦与碎麦挥发性香气成分差异。方法 采用顶空固相微萃取(headspace solid-phase microextraction, HS-SPME)技术联用电子鼻(electronic nose, E-Nose)与气相色谱-质谱法(gas chromatography-mass spectrometry, GC-MS)分析小麦与碎麦香气成分, 通过多元统计分析正交偏最小二乘法(orthogonal partial least squares-discriminant analysis, OPLS-DA)挖掘小麦与碎麦差异挥发物。结果 小麦与碎麦的香气成分存在显著差异, 整体上小麦挥发物响应强度高于碎麦, 小麦变成碎麦后部分香气值损失, 氧化分子和芳香化合物显著降低, 脂肪酸类化合物变化不明显, 酮类和胺类化合响应值较为接近。通过GC-MS共鉴定出42种化合物, 10种挥发物组分在小麦和碎麦共同检出, 小麦和碎麦中烷烃类化合物较多, 小麦主要挥发物为柠檬烯、十五烯和壬醛; 碎麦的主要挥发物是苯乙烯, 柠檬烯和间乙基甲苯。基于小麦和碎麦挥发组分建立了OPLS-DA评估模型, 共筛选出7种差异挥发物判别小麦品质。结论 本研究成功建立了区别小麦和碎麦的方法, 分析了小麦与碎麦香气成分差异, 为小麦品质判别提供了科学依据。     

Removal of phenolic compounds in the production of high-quality canola protein isolates

Phenolic compounds are a major cause of the dark colour and undesirable taste of canola protein isolates. Based on our previous study of phenolic–protein interactions, a variety of treatments were tested for the removal of phenolic compounds from canola proteins. The combined use of these treatments was able to reduce the phenolic content of the products by 80–90%. Thus modified, the process produced two canola protein isolates, both of high protein content (>85%), low in phenolic acids (∼200 mg/100 g), and essentially free of condensed tannins. Colour measurement and sensory evaluation confirmed that the removal of phenolic compounds improved the colour and taste of canola protein isolates.     

Milling fractions fatty acid composition of common (Fagopyrum esculentum Moench) and tartary (Fagopyrum tataricum (L.) Gaertn) buckwheat

The objective of the present study was to determine the composition of fatty acids in the whole grain, hulls, bran and the light flour of common (Fagopyrum esculentum Moench) and Tartary (Fagopyrum tataricum (L.) Gaertn) buckwheat harvested in two consecutive years. Fatty acid composition for different milling fractions was determined as methyl esters using gas chromatography. Nine fatty acids were determined: lauric (12:0), myristic (14:0), palmitic (16:0), palmitoleic (16:1), stearic (18:0), oleic (C18:1; n-9), linoleic (C18:2; n-6), α-linolenic (C18:3; n-3) and arachidic (20:0) acid. The highest relative content was determined for linoleic acid (from 35.54 to 47.57%), followed by oleic acid (from 20.96 to 40.76%) and palmitic acid (from 13.86 to 26.42%). The total fatty acid content was the highest in bran (up to 62.64 g/kg), followed by whole grains (up to 22.93 g/kg), light flour (up to 9.69 g/kg) and hulls (up to 5.87 g/kg). Saturated fatty acid content was the highest in the hulls and the lowest in the bran. Polyunsaturated fatty acid content was the highest in light flour. High positive correlations were found between saturated fatty acids with 18 carbon atoms or less.     

Colorimetric sensor arrays based on chemo-responsive dyes for food odor visualization

BackgroundThe colorimetric sensor array technology simulates human olfaction to analyze, identify and examine complex gas and volatility based on chem-responsive dyes. Unlike human olfaction and electronic noses, colorimetric sensor array is more objective and not susceptible to interference. In additional, with the visualization, rapidity and non-destruction of analysis, colorimetric sensor array has been increasingly applied in food science and industry.Scope and approachThis review focuses on the colorimetric sensor array technology and its major applications in food industry. Technical considerations associated with the chemo-responsive dyes, substrate materials, and data processing methods are discussed. In application, any type of food samples including solid, liquid food samples could be directly analyzed using colorimetric sensor array. Additionally, the recent development, and future research trends are also involved.Key findings and conclusionsThe colorimetric sensor array technology offers an exciting method to establish the correlation between the output of a colorimetric sensor array and the odor components, thereby enabling visual quantification of odors. It provides a potential odor-image-based monitoring tool for the rapid, reliable and in-line assessment of food safety and quality.     

Selenium in cereals: Insight into species of the element from total amount

Selenium (Se) is a trace mineral micronutrient essential for human health. The diet is the main source of Se intake. Se-deficiency is associated with many diseases, and up to 1 billion people suffer from Se-deficiency worldwide. Cereals are considered a good choice for Se intake due to their daily consumption as staple foods. Much attention has been paid to the contents of Se in cereals and other foods. Se-enriched cereals are produced by biofortification. Notably, the gap between the nutritional and toxic levels of Se is fairly narrow. The chemical structures of Se compounds, rather than their total contents, contribute to the bioavailability, bioactivity, and toxicity of Se. Organic Se species show better bioavailability, higher nutritional value, and less toxicity than inorganic species. In this paper, we reviewed the total content of Se in cereals, Se speciation methods, and the biological effects of Se species on human health. Selenomethionine (SeMet) is generally the most prevalent and important Se species in cereal grains. In conclusion, Se species should be considered in addition to the total Se content when evaluating the nutritional and toxic values of foods such as cereals.