青砖茶压制压力优化及GCG近红外快速检测模型建立

青砖茶压制压力的选择至关重要,为探求压力与青砖茶品质及内含成分间的相互关系,并尝试对关键成分进行快速预测。以青砖茶为研究对象,设置了5个等级的压力值,通过感官审评和相关关系法分析了最佳压力值与品质和内含成分间的相关关系;应用标准变量变换、多元散射校正、一阶导数和二阶导数及组合方法进行降噪处理,应用反向区间偏最小二乘法筛选特征光谱区间并进行主成分分析,将主成分分别输入到3种信息传递函数的jump connection nets结构人工神经网络中建立定量分析模型。结果表明,最佳压力值为18MPa;关键内含成分为:没食子儿茶素没食子酸酯(Gallocatechin Gallate,GCG)(P<0.05);最佳预处理方法:多元散射校正+一阶导数组合方法;特征光谱区间:9 734.9~10 000,8 924.9~9 191.1,5 368.9~5 638.8,7 011.9~7 281.9,6 190.4~6 460.4,4 821.2~5 091.2,9 194.9~9 461.1,7 559.6~7 829.6,5 916.5~6 186.5 cm^-1,前3个主成分累积贡献率为97.82%,以应用tanh传递函数建立的GCG人工神经网络模型结果最佳(Rp^2=0.980,RMSEP=0.027),并有较好的实际应用效果(Rp^2=0.948,RMSEP=0.041)。研究结果为其它重量规格青砖茶产品的研发和品质的快速检测奠定了理论基础。     

Characterization of espresso coffee aroma by static headspace GC-MS and sensory flavor profile.

The aromas of three espresso coffee (EC) samples from different botanical varieties and types of roast (Arabica coffee, Robusta natural blend, and Robusta Torrefacto blend (special roast by adding sugar)) were studied by static headspace GC-MS and sensory flavor profile analysis. Seventy-seven compounds were identified in all of the EC samples. Among them, 13 key odorants have been quantified and correlated with their flavor notes by applying multivariate statistical methods. Some correlations have been found in the EC samples: some aldehydes with fruity flavors, diones with buttery flavors, and pyrazines with earthy/musty, roasty/burnt, and woody/papery flavors. By applying principal component analysis (PCA), Arabica and Robusta samples were separated successfully by principal component 1 (60.7% of variance), and Torrefacto and Natural Robusta EC samples were separated by principal component 2 (28.1% of total variance). With PCA, the aroma characterization of each EC sample could be observed. A very simple discriminant function using some key odorants was obtained by discriminant analysis, allowing the classification of each EC sample into its respective group with a success rate of 100%.     

Effect of sucrose on functional properties of soy globulins: adsorption and foam characteristics

In this contribution, we have analyzed the effect of sucrose on dynamic interfacial (dynamic surface pressure and surface dilatational properties) and foaming (foam capacity and foam stability) characteristics of soy globulins (7S and 11S). The protein (at 1 x 10(-3), 1 x 10(-2), 0.1, and 1 wt %) and sucrose (at 0, 0.25, 0.5, and 1.0 M) concentrations in aqueous solution and the pH (at 5 and 7), and ionic strength (at 0.05 and 0.5 M) were analyzed as variables. The temperature was maintained constant at 20 degrees C. We have observed the following. (i) The dynamics of adsorption (presence of a lag period, diffusion, and penetration at the air-water interface) of soy globulins depend on the peculiar molecular features of proteins (7S or 11S soy globulin) and the level of association/dissociation of these proteins by varying the pH and ionic strength, as well as the effect of sucrose in the aqueous phase on the unfolding of the protein. The rate of adsorption increases with the protein concentration in solution, at pH 7 compared to pH 5, at high ionic strength, and in the absence of sucrose. (ii) The surface dilatational properties reflect the fact that soy globulin adsorbed films exhibit viscoelastic behavior. The surface dilatational modulus increases at pH 7 compared to pH 5, but decreases with the addition of sucrose into the aqueous phase. (iii) The rate of adsorption and surface dilatational properties (surface dilatational modulus and phase angle) during adsorption at the air-water interface play an important role in the formation of foams generated from aqueous solutions of soy globulins. (iv) The increased interfacial adsorption (at high surface pressures) and the combined effects of interfacial adsorption and interfacial interactions between adsorbed soy globulin molecules (at high surface dilatational modulus) can explain the higher stability of the foam, with few exceptions.     

Identification and quantitation of key aroma compounds formed in Maillard-type reactions of fructose with cysteamine or isothiaproline (1,3-thiazolidine-2-carboxylic acid)

Fructose was reacted in the presence of either cysteamine (model A) or isothiaproline (model B) in aqueous buffer at 145 degrees C and pH 7.0. Application of an aroma extract dilution analysis on the bulk of the volatile compounds formed in model A revealed 5-acetyl-3,4-dihydro-2H-1,4-thiazine (19), N-(2-mercaptoethyl)-1,3-thiazolidine (16), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (15), and 2-acetyl-2-thiazoline (11) as the key aroma compounds among the 10 odorants detected. A similar set of aroma compounds was formed when isothiaproline was reacted (model B), but the flavor dilution factors were generally lower. Substitution of the buffer by silica gel/water (9 + 1 w/w) in both models and application of 150 degrees C for 10 min also gave the same key odorants from both thio compounds; however, under these conditions isothiaproline was the better precursor of, in particular, 19 and 11. Quantitative measurements performed by means of stable isotope dilution assays revealed a significant effect of the pH on odorant formation. For example, in model A, formation of 19 as well as of 11 was suppressed at pH values <5.0. A clear maximum was, however, found for 19 at pH 7.0 (approximately 1 mol % yield), whereas 11 increased with increasing pH from 7.0 to 9.0.     

A new insight into the formation of odor active carbonyls by thermally-induced degradation of phospholipids in self-assembly structures

The role of molecular organization in heated aqueous dispersions of egg phosphatidylcholine (PC) and egg phosphatidylethanolamine (PE) was studied with respect to the formation of key odorants. Evidence was found for the crucial role of self-assembly structures adopted by phospholipid molecules on the quantitative composition of volatile constituents. The concentrations of seven aldehydes and one vinyl ketone were determined by isotope dilution assay in heated aqueous dispersions of PC and PE present in various ratios. Addition of PE to PC drastically decreased the amount of (E,E)-2,4-decadienal formed, which cannot be explained by the differences in the fatty acid composition of PC and PE. The free amino group in PE does not explain this phenomenon either, as replacing PE by phosphatidic acid distearylester also reduced the amounts of (E,E)-2,4-decadienal. We suggest that the type of self-assembly structure adopted by phospholipids in water significantly influences the reaction yields. However, the mechanisms leading to the preferred formation of phospholipid-derived odorants in a lamellar phase, as compared to the reversed hexagonal phase, remain unknown.     

主成分分析方法在长期施肥土壤质量评价中的应用

以长期定位试验玉米季成熟期6种土壤微生物活性和9种土壤化学性质指标组成的土壤生物肥力性质为评价指标对不同施肥条件下的土壤质量水平进行主成分分析。结果表明,经18年连续不同施肥处理后,各土壤性质在处理间均产生显著差异,但各土壤性质在处理间的变化趋势并不完全一致。上述15个土壤性质指标最终可以用两个主成分来综合表征土壤质量,其中有机C、全N、碱解N、pH值、微生物生物量C、微生物生物量N、脲酶、转化酶、FDA酶和脱氢酶活性等10个土壤性质在第一主成分（PC1）上有较高因子负荷;全P、全K、速效N和速效P在第二主成分（PC2）上有较高的因子负荷。同时各施肥土壤质量水平在主成分1上的分异程度大于主成分2。根据两个主成分的综合得分结果显示,长期不同施肥土壤质量水平高低依次表现为OM＞1/2OM＞NPK＞NP＞PK＞NK＞CK。     

The composition of the soil solution as influenced by fertilization and nutrient uptake

The composition of the soil solution in unfertilized and well-fertilized plots of three long-term field experiments has been determined at the beginning and at the end of the growing season. All the plots were manured and the K and P fertilizers given in the autumn before the growth of sugar beet. N was applied in the spring, 3–4 weeks before the first soil sampling.The soil solution was removed at a pressure of 5 atm. The composition and the corresponding osmotic pressure were calculated for the moisture contents at field capacity and wilting point.In spring the salt concentrations, cations + anions, at the field capacity were in the range 91–97 mmoles/l in the fertilized plots. In autumn the concentration had dropped to 13.9–20.3, a decrease of 78–85%. At the wilting point, the concentrations in spring were as high as 211–307 mmoles/l and in autumn 31.5–69 mmoles/l. The corresponding osmotic pressures at field capacity in the spring ranged 2.2–2.3 atm. and at wilting point 5.1–7.4 atm.In spring the unfertilized plots showed concentrations of 16–21 mmoles/l and osmotic pressures of 0.38–0.51 atm., the values decreasing 52–65% during the growing season.It was pointed out that the high soil-solution concentration and osmotic pressure at low moisture contents may lead to an unfavourable effect on root metabolism. Further, the obscuring effect of the varying soil-solution concentration on the relationships between root ion exchange and nutrient uptake by plants has been discussed.     

用电子鼻区分霉变燕麦及其传感器阵列优化

应用电子鼻对燕麦（Avena sativa L）霉变程度进行区分,为了提高区分准确度,对电子鼻传感器阵列进行了优化的研究。每天随机选择10个燕麦样品进行电子鼻检测,试验连续进行5 d,将检测数据耦合入非线性双稳态随机共振系统,以外部Gaussian白噪声激励系统产生共振,选择输出信噪比特征值进行主成分分析,初期试验主成分1和主成分2贡献率之和为96.43%,且相同霉变程度样品离散度较大,不同霉变程度样品之间距离较近。为了提高电子鼻对霉变燕麦样品区分效果,进行了电子鼻传感器负荷加载分析,优化选择了传感器阵列,优化后主成分1和主成分2贡献率之和为99.31%,相同霉变程度燕麦样品的聚合度更高,使不同霉变程度燕麦样品之间的区分更加明显,为进一步的定量化检测奠定了基础。     

Aroma Stability of Millet Powder During Storage and Effects of Cooking Methods and Antioxidant Treatment

Foxtail millet is a cereal crop that contains high levels of unsaturated fatty acids, so that processed food such as instant millet powder is susceptible to lipid oxidation, which gradually leads to deteriorated flavor and quality. In this work, volatiles of millet powder samples with or without storage at room temperature for 12 months were extracted and analyzed by gas chromatography–olfactometry/mass spectrometry. In fresh steamed millet powder, hexanal, 2‐pentylfuran, and 3‐octen‐2‐one might be dominant odorants, whereas in deteriorated steamed millet powder, volatiles such as 1‐octen‐3‐ol, (E)‐2‐octen‐1‐ol, (E)‐2‐octenal, 3‐nonen‐2‐one, (E)‐2‐nonenal, decanal, 2‐undecanone, and 2‐methylnaphthalene emerged or increased over time, among which 1‐octen‐3‐ol and (E)‐2‐nonenal were highly responsible for its rancid flavor. We also compared millet powder prepared with two different processing methods, steaming and extrusion. Compared with steaming, extrusion was a cooking method of millet that helped slow the generation of oxidized flavor to some extent. When 0.04 g/kg (w/w millet) of ascorbyl palmitate was added as an antioxidant before drying, the production of unpleasant odorants was significantly inhibited, so that the quality of final products was improved. Analysis of odorants can be an alternative method for evaluating the storage stability of processed food.     

Effects of the combination of hydrophobic polypeptides, iso-alpha acids, and malto-oligosaccharides on beer foam stability

The influence of hydrophobic polypeptides concentrated in beer foam, together with the composition of iso-alpha acids and the content of malto-oligosaccharides in beer on foam stability, has been investigated. The objective was to find out whether a shortage of one of these positive contributors to foam stability could be compensated for by an increased presence of another or whether optimum levels of each contributor is necessary. For that purpose, an image analysis method to evaluate beer foam quality was developed. The foam collapse time was the parameter chosen to group beers according to their foam stability. Profiles of hydrophobic polypeptides that concentrate in beer foam, iso-alpha acids, and malto-oligosaccharides of 14 beer brands were acquired by high-performance liquid chromatography. Principal component analysis (PCA) was performed to show the relationship between beer brands and its composition. Beers that contained propylene glycol alginate as a foam enhancer showed high foam stability except for one beer, which had a low content of hydrophobic polypeptides, thereby highlighting the requirement of threshold levels of hydrophobic polypeptides to obtain stable foam. The data of samples that were devoid of a foam additive were subjected to a discriminant statistical analysis. Foam stability declined in proportion to decreases in hydrophobic polypeptides and to a lesser extent to decreases in iso-alpha-acid contents. Apparently, the content of malto-oligosaccharides were found to have no major influence on foam stability. The model of discriminate analysis was found to explain 100% of the variance in data with 85.2% success in classifying all samples according to the model, suggesting that foam stability is mainly governed by the beer constituents evaluated in this study.     

基于机器视觉的板栗分级检测方法

为实现合格和缺陷板栗的分级,研究了1种基于BP神经网络与板栗图像特征的板栗分级方法。试验以罗田板栗为研究对象,提取的颜色及纹理等8个特征值,通过主成分分析提取相应的主成分得分向量构成模式识别的输入。利用BP神经网络方法建立了板栗分级模型。试验结果表明,在图像信息主成分因子数为3,中间层节点数为12时,建立的模型最佳,模型训练时的回判率为100%,预测时识别率达到了91.67%。研究结果表明基于机器视觉技术的针对缺陷板栗分级检测方法是可行的。     

基于主成分分析的高丛蓝莓品种果实品质综合评价

比较分析不同品种蓝莓果实品质特性,确定代表性品质指标,建立蓝莓品质综合评价体系,为蓝莓品质合理评价和优良蓝莓品种筛选提供理论参考。以26个高丛蓝莓品种果实为材料,测定其11项品质指标（单果质量、果实横径、果实纵径、果形指数、果实硬度、可溶性固形物质量分数可溶性糖质量分数、可滴定酸质量分数、糖酸比、维生素C质量分数、花色苷质量分数）,并采用主成分分析方法进行果实品质综合评价。结果表明：26个蓝莓品种的11项果实品质性状中糖酸比、可滴定酸质量分数、单果质量和花色苷质量分数的变异系数较大,其变异系数分别为33.67%、32.25%、30.84%和28.48%。通过主成分分析确定单果质量、果形指数、可溶性糖质量分数、可滴定酸质量分数、花色苷质量分数和果实硬度可作为评价蓝莓果实品质的代表性指标;建立综合品质评价模型,并依据各品种的综合品质得分进行优良度排序,得分排名前10位的蓝莓品种依次为‘大果蓝金’‘莱格西’‘公爵’‘日出’‘维口’‘蓝片‘早蓝’‘蓝丰’‘爱国者’‘红利’,研究结果为大连地区蓝莓品种合理开发和应用提供了依据。     

基于近红外光谱和机器视觉的多信息融合技术评判茶叶品质

首次提出利用近红外光谱和机器视觉的多传感信息融合技术评判茶叶品质.试验以4个等级的炒青绿茶为试验对象,对获取的图像特征信息和光谱特征信息,通过主成分分析提取相应的主成分得分向量构成模式识别的输入.利用BP神经网络方法建立茶叶综合品质评判模型.在模型的建立过程中,对各个信息的主成分因子数进行了优化.从试验的结果看,在图像信息主成分因子数等于6,光谱信息主成分因子数等于3时,建立的模型最佳,模型训练时的回判率为99%,预测时的识别率为89%.研究结果表明基于近红外光谱和机器视觉技术的多传感信息融合技术评判茶叶综合品质的方法是可行的,评判结果的准确性和稳定性都较单个信息模型有所提高.     

Formulation engineering can improve the interfacial and foaming properties of soy globulins

In this contribution, we have analyzed the effect of different strategies, such as change of pH (5 or 7) or ionic strength (at 0.05 and 0.5 M), and addition of sucrose (at 1 M) and Tween 20 (at 1 x 10(-4) M) on interfacial characteristics (adsorption, structure, dynamics of adsorption, and surface dilatational properties) and foam properties (foam capacity and stability) of soy globulins (7S and 11S at 0.1 wt %). We have observed that (1) the adsorption (presence of a lag period, diffusion, and penetration at the air-water interface) of soy globulins depends on the modification in the 11S/7S ratio and on the level of association/dissociation of these proteins by varying the pH and ionic strength (I), the effect of sucrose on the unfolding of the protein, and the competitive adsorption between protein and Tween 20 in the aqueous phase. The rate of adsorption increases at pH 7, at high ionic strength, and in the presence of sucrose. (2) The surface dilatational properties reflect the fact that soy globulin adsorbed films exhibit viscoelastic behavior but do not have the capacity to form a gel-like elastic film. The surface dilatational modulus increases at pH 7 and at high ionic strength but decreases with the addition of sucrose or Tween 20 into the aqueous phase. (3) The rate of adsorption and surface dilatational properties (surface dilatational modulus and phase angle) during adsorption at the air-water interface plays an important role in the formation of foams generated from aqueous solutions of soy globulins. However, the dynamic surface pressure and dilatational modulus are not enough to explain the stability of the foam.     

Preparation of spread oils meeting U.S. Food and Drug Administration Labeling requirements for trans fatty acids via pressure-controlled hydrogenation

On July 11, 2003, the U.S. Food and Drug Administration (FDA) announced final regulations for trans fatty acid (TFA) labeling. By January 1, 2006, the TFA content of foods must be labeled as a separate line on the Nutrition Facts label. Products containing <0.5 g of TFA/14 g serving may be declared as zero. This paper describes technologies allowing compliance with TFA labeling requirements. Soybean oil was hydrogenated in a 2-L vessel at temperatures ranging from 120 to 170 degrees C at a hydrogen pressure of 200 psi. A commercial nickel-supported catalyst (25% Ni) was used at 0.02% Ni by weight of oil. The hydrogenated oils were characterized for fatty acid composition, solid fat content, and melting point. Compared to commercially processed soybean oil basestocks that typically contain approximately 40% TFA, those obtained at lower temperatures and higher pressures contain >56% less TFA. Basestocks prepared in the laboratory when blended with liquid soybean oil will yield spread oils meeting FDA labeling requirements for zero TFA, that is, <0.5 g of TFA/serving.     

Statistical and geostatistical techniques for geospatial modeling of soil cation exchange capacity

Soil cation exchange capacity (CEC) is a main criterion of soil quality and pollutant sequestration capacity. This research was carried out to evaluate cokriging prediction map of soil CEC spatial variability with the principal components derived from soil physical and chemical properties. Two hundred and forty-seven soil samples were collected that 75% of them were used for training soil CEC and 25% for testing of prediction. The first principal component (PC1) was highly correlated with soil CEC (r = 0.81, P < 0.01), whiles there was no significant correlation between CEC and PC2 (r = -0.19). Then, the PC1 was used as an auxiliary variable for the prediction of soil CEC in cokriging method. The determination coefficient (R²) of cross-validation for the test dataset was 0.47 for kriging and 0.71 for cokriging. Therefore, according to the results, principal components that have the highest positive and significant correlation with the dependent variable have the most potential for cokriging prediction.     

基于主成分与聚类分析的苹果加工品质评价

为了探讨苹果品种间理化品质的差异,给选育新品种和苹果合理加工利用提供理论支持,采集了30个苹果品种为试材进行模式识别分析。该试验所用苹果在2011年8-10月份按照苹果可采成熟度(九成熟)在辽宁省兴城市国家种质资源圃进行采集。试验测定了单果质量、体积、密度、果皮颜色、硬度、糖酸比、维生素C等20项理化品质指标,采用描述性统计、主成分和聚类分析方法对苹果品种和品质关系进行了分析。结果显示,30个品种苹果的密度、果型指数和含水率3项指标未表现出差异。对剩余17项品质指标进行了主成分分析,依据主成分解释总变量和碎石图提取了6个主成分反映原变量的82.3%的信息。第一主成分主要综合了可滴定酸、糖酸比及固酸比的信息即口尝品质因子;第二主成分主要综合了L值,a值和b值的信息,命名为颜色因子;其余主成分依次为甜度因子、质构因子、内在品质因子和果个大小因子。结合主成分得分图直观地显示了苹果品种和理化指标间关系:辽伏、理想、早金冠和瑞光分布在PC1和PC2的正向区间,糖酸比和固酸比值较大、口感好,但是果皮颜色较绿,是品质较好的早熟苹果;寒富、赤阳和红富士依次落在PC1和PC2第四区间,食用品质好、果皮颜色较红,是较为常见的晚熟苹果。分布在第二区间的普利阿姆,白星,Pvma果皮颜色绿且口感酸涩,不适宜鲜食,这些品种可能较为适宜进行加工。第三区间品种固酸比、甜酸比取值较小但是果皮颜色红,为选育果皮颜色受消费者喜爱且内在品质好的早熟品种提供了理论支持。聚类分析将30个品种苹果分为5类,聚类结果与主成分得分图结果基本一致,该试验初步判定30个品种苹果是否适宜鲜食,为苹果品种选育和加工应用利用提供理论依据。     

Beta-carotene isomer composition of sub- and supercritical carbon dioxide extracts. Antioxidant activity measurement

In the present work sub- and supercritical extraction conditions using carbon dioxide were studied in order to obtain extracts with different compositions from the green microalgae Dunaliella salina. Different compositions of beta-carotene isomers were identified in the extracts by using HPLC-DAD. Also, antioxidant activity of the extracts was measured using a TEAC assay. An experimental design was applied considering two factors, extraction pressure and temperature, in a wide range of values, trying to maximize the extraction yield. Higher yields were obtained at high pressures and low temperatures, that is, at higher CO2 densities. Attempts were made to correlate the antioxidant activity of the extracts with their chemical composition by means of principal component analysis. A certain relationship was found between their antioxidant activity and the isomeric composition of beta-carotenes. As a result, an original equation is proposed to predict the antioxidant activity of extracts from D. salina in terms of the ratio 9-cis-beta-carotene/all-trans-beta-carotene, the concentration of alpha-carotene, and, especially, the concentration of 9-cis-beta-carotene.     

Synergistic effect of high and low molecular weight molecules in the foamability and foam stability of sparkling wines

The foam of sparkling wines is a key parameter of their quality. However, the compounds that are directly involved in foam formation and stabilization are not yet completely established. In this work, seven sparkling wines were produced in Bairrada appellation (Portugal) under different conditions and their foaming properties evaluated using a Mosalux-based device. Fractionation of the sparkling wines into four independent fractions, (1) high molecular weight material, with molecular weight higher than 12 kDa (HMW), (2) hydrophilic material with molecular weigh between 1 and 12 kDa (AqIMW), (3) hydrophobic material with molecular weigh between 1 and 12 kDa (MeIMW), and (4) hydrophobic material with a molecular weight lower than 1 kDa (MeLMW), allowed the observation that the wines presenting the lower foam stability were those that presented lower amounts of the MeLMW fraction. The fraction that presented the best foam stability was HMW. When HMW is combined with MeLMW fraction, the foam stability largely increased. This increase was even larger, approaching the foam stability of the sparkling wine, when HMW was combined with the less hydrophobic subfraction of MeLMW (fraction 3). Electrospray tandem mass spectrometry (ESI-MS/MS) of fraction 3 allowed the assignment of polyethylene glycol oligomers (n = 5-11) and diethylene glycol 8-hydroxytridecanoate glyceryl acetate. To observe if these molecules occur in sparkling wine foam, the MeLMW was recovered directly from the sparkling wine foam and was also analyzed by ESI-MS/MS. The presence of monoacylglycerols of palmitic and stearic acids, as well as four glycerylethylene glycol fatty acid derivatives, was observed. These surface active compounds are preferentially partitioned by the sparkling wine foam rather than the liquid phase, allowing the inference of their role as key components in the promotion and stabilization of sparkling wine foam.