基于二元Logistic回归分析的苹果汁鉴伪模型的建立

苹果汁中特征有机酸指纹图谱可以用来鉴别苹果汁掺假。本文共收集了170个中国产苹果样本,通过高效液相色谱法测定样本中有机酸的种类及含量。数据与现有文献中相关数据不完全吻合,但所得数据反应的是中国不同产区苹果中有机酸数据特征。在测得的有机酸种类和含量的基础上利用二元Logistic回归分析方法建立了一个判别模型,用以区别掺假苹果汁。模型为：π=1/[1+exp(79.545X1+14.255X2+ 3.4X3-5.02)],此模型的精确度和重现率分别为87.4%和94.51%。统计数据显示该模型判别效果良好,可用于苹果汁的质量控制。     

磁性壳聚糖微球吸附苹果汁有机酸的动力学及热力学特性

为充分利用中国丰富的苹果资源,开发多品类的苹果深加工产品,以磁性壳聚糖微球为吸附剂,通过磁分离技术,吸附获得苹果汁中的天然有机酸,并对其吸附过程进行研究。利用Lagergren准一级动力学方程、准二级动力学方程、Elovich方程及内扩散方程对吸附反应动力学过程进行拟合;利用Langmuir等温吸附模型、Freundlich等温吸附模型及Temkin等温吸附模型对吸附等温数据进行拟合,并对其吸附反应热力学特性进行分析。通过比较线性拟合方程的决定系数,发现磁性壳聚糖微球吸附苹果汁中有机酸的动力学过程更加符合Lagergren准二级动力学模型,吸附温度越高,吸附速率常数和初始吸附速率越大,但平衡吸附量越低。等温吸附过程更加符合Langmuir等温吸附模型,表明该吸附过程更趋向于单分子层的化学吸附。298 K时,有机酸的饱和吸附量可达到188.679 2 mg/g,表明磁性壳聚糖微球是苹果汁中有机酸的1种高效吸附剂。热力学参数ΔG°0,ΔH°0,ΔS°0,表明磁性壳聚糖微球对苹果汁有机酸的吸附过程为熵增加的可自发进行的放热过程。动力学及热力学结果为磁性壳聚糖微球吸附苹果汁有机酸的研究提供了理论基础与技术支持。     

近红外光谱联合CARS-PLS-LDA的山茶油检测

为了寻找快速判别山茶油掺假的检测方法,本研究利用近红外光谱技术对掺杂大豆没油山茶油进行掺假检测研究.试验在350～1 800 nm波段范围内采集样本的透射光谱,利用CARS方法筛选重要的波长变量,应用偏最小二乘-线性判别分析(PLS-LDA)建立山茶油掺假的判别模型,并与未经变量优选的判别模型进行比较.结果表明,近红外光谱技术联合CARS-PLS-LDA方法可以有效判别纯山茶油和掺假山茶油,校正集、预测集及独立样本组样本的判别正确率、灵敏度及特异性均为100％.CARS-PLS-LDA判别模型性能优于未经变量优选的判别模型,表明CARS方法可以有效筛选重要波长变量,能简化判别模型及提高判别模型的稳定性和判别精度.本研究可为山茶油掺假快速检测提供理论依据.     

基于生物散斑图像和惯性矩谱分析的牛肉掺腐检测

牛肉掺假严重危害消费者的健康与经济利益,因此对牛肉掺假进行无损检测具有重要意义。该文基于生物散斑技术对牛肉掺假进行定量检测。试验将新鲜牛肉和非新鲜牛肉按不同比例(0、1%、3%、5%~60%(5%梯度)和100%)混合制备掺假样本,并采集样本的生物散斑图像。针对单列惯性矩(inertia moment,IM)表征样本生物活性存在稳定性差的问题,首次提出惯性矩谱(IM谱)分析的方法并用于建立基于支持向量回归机(support vector regression machine,SVR)的牛肉掺假检测模型。结果表明基于IM谱建立的SVR模型能较为准确预测牛肉中掺假物含量,校正集和测试集的决定系数分别为0.85和0.81,均方根误差分别为0.12和0.11。该研究证明了利用生物散斑技术和惯性矩谱分析方法对新鲜牛肉中掺杂腐败牛肉进行定量检测是可行的。     

微波预处理原料对苹果汁褐变的影响

为了防止苹果汁在贮藏过程中褐变,采用不同的微波功率和时间预处理原料苹果,研究微波预处理对苹果汁褐变的影响。结果表明,微波处理可以提高苹果汁的色值,降低多酚氧化酶的活性,引起氨基态氮含量的下降,并使苹果汁的酸度略微提高。在微波功率为720～900 W,处理时间75～125 s时,果汁色值较高。室温贮存45 d后,微波功率900 W,时间为100 s处理的果块,果汁色值为67.8,比未经微波处理的高91.5%。微波预处理是防止苹果汁褐变的一种简便安全、合理经济的加工方法。     

烤烟有机酸含量与土壤理化性状关系分析

对河南省2004年379个烤烟样品烟叶的有机酸含量进行了分析,并采用SPSS13.0软件,研究了烟叶的18种有机酸和对应土壤样品的23个土壤理化性状指标的相关关系。结果表明,河南省不同产区烤烟烟叶有机酸总量基本接近,但是不同种类有机酸的含量差异较大。各种有机酸中,以苹果酸的含量最高,柠檬酸含量次之。三类有机酸含量中,以多元羧酸的含量最高,不饱和脂肪酸含量次之,饱和脂肪酸含量最低。统计分析表明,土壤的23项理化指标和烟叶有机酸含量有不同程度的相关关系,其中以全磷、速效钾、有机质、全氮、镁、pH和钠等6个指标和烟叶有机酸含量关系较密切。采用逐步回归分析的方法,构建了土壤理化指标与烟叶有机酸含量的回归方程,逐步回归方程均达到显著水平。     

果园土壤中结合态腐殖质组成特征

通过化学分析方法研究延边地区典型苹果梨园盛果期土壤剖面中结合态腐殖质的空间分布特征.结果表明:(1)A1层(0-22 cm)松结态腐殖质含量表现为苹果梨园＞荒地,高出荒地42.61％,至A2层(22-53 cm)2种土壤松结合态腐殖质含量下降幅度分别60.79％,36.45％;苹果梨园土壤A1层的松结态腐殖质表聚现象比荒地土壤剧烈;在A1、A2层,松结态FA含量表现为苹果梨园＜荒地,HA/FA比以苹果梨园明显高于荒地.(2)苹果梨园稳结态腐殖质含量随土壤深度增加而下降,荒地土壤呈先升后降再升趋势;A1、A2层稳结态腐殖质含量表现为苹果梨园＜荒地;苹果梨园稳结态FA含量随土壤深度增加呈现升一降一升趋势;苹果梨园稳结态HA含量随土壤深度加深而减小,且A2层稳结态FA含量表现为苹果梨园明显小于荒地;A2层HA/FA比表现为荒地＞苹果梨园.(3)2种土壤紧结态腐殖质含量均随土层深度增加而减小;A1层表现为苹果梨园＜荒地,A2层表现为苹果梨园＞荒地.(4)A1层松结态腐殖质相对含量表现为苹果梨园＞荒地,A2层相反;A1、A2层稳结态腐殖质含量表现为苹果梨园＜荒地;紧结态腐殖质含量相当.苹果梨园松结态腐殖质含量表现为A1＞A2,稳结态腐殖质含量表现为A1＜A2.松/紧比在A1层表现为苹果梨园＞荒地,A2层表现为苹果梨园＜荒地;苹果梨园土壤A1层松结态∶稳结态∶紧结态为3.4∶2.0∶4.6,A2层为2.1∶3.2∶4.7.     

60Co-γ辐照对苹果汁中有机磷农药降解及品质影响

为了寻求一种能最大限度保持苹果汁品质又能有效降解有机磷农药残留的技术方法,该文采用0～9kCy的60Co-γ射线辐照方法,对苹果汁中国家标准规定必检的9种有机磷农药进行了系统的降解试验.结果表明:60Co-γ射线辐照处理对苹果汁中杀螟硫磷、对硫磷、甲基对硫磷、甲拌磷、毒死蜱降解效果最为显著,最高降解率均在85%以上;对苹果汁中甲胺磷、乙酰甲胺磷、马拉硫磷和乐果的降解效果不显著,最高降解率仅为35%;在0～9 kGy辐照剂量范围内降解苹果汁中有机磷农药的同时,会使苹果汁中的可溶性固形物、葡萄糖、果糖、蔗糖及总糖含量轻微降低,苹果汁的总酸度有所增加,苹果汁的色值及透光率提高:综合分析60Co-γ射线辐照对苹果汁中有机磷农药的实际降解效果及对苹果汁主要理化指标的影响,选用5kCy的辐照剂量已完全使苹果汁中的有机磷农药残留降低到一个很低的水平,又不会对苹果汁出口主要理化指标造成影响.     

超滤技术对苹果汁加工中主要芳香成分影响的研究

选用青香蕉苹果和国光苹果为原料,研究了超滤对苹果汁主要芳香成分的影响。苹果汁用国产平板膜超滤机澄清,用顶空动态采样法收集芳香物,用气相色谱法分析芳香成分。通过比较超滤前后青香蕉和国光苹果汁芳香成分的变化,截留分子量为10000daltons的聚砜膜PS—10对苹果汁芳香成分保留有良好效果,优于PS—30,PS—60和PS—80;聚砜膜对醇类芳香成分保留优于酯类芳香成分,并对其截留机理作了初步探讨,认为吸附起主要作用。芳香物回收实验表明,12000Pa,50℃为苹果汁芳香成分回收的适宜条件。     

基于电学参数的苹果可溶性固形物含量预测

为实现苹果可溶性固形物含量的无损检测，该研究提出了一种长短期记忆编解码和多层感知机（LSTMED-MLP,long short-term memory encoder-decoder-multi-layer perceptron）融合的介电特征预测方法。在0.158～3 980 kHz频率范围内的9个频率点下，采用介电谱测量仪获取300个富士苹果的电学参数，其中每个频率点对应15项电学参数，即每个苹果对应135项电学特性参数，之后通过苹果基因组学理化分析方法，获取可溶性固形物含量；根据电学参数与可溶性固形物含量，构建苹果关键基因组学参数的回归预测模型。为简化模型输入，提取样本变量特征，使用主成分分析（principal component analysis,PCA）和LSTMED模型，提取每个样本的40项特征值，作为非线性回归模型多层感知机（MLP）和XGBoost的输入，建立可溶性固形物含量预测模型。试验结果表明，LSTMED具有更好的适用性，且LSTMED-MLP模型的预测效果最好，在校正集和预测集上，决定系数分别为0.95和0.90，均方根误差分别为0.77和0.84，且对不同种...     

Detection of sugar adulterants in apple juice using fourier transform infrared spectroscopy and chemometrics

Fourier transform infrared spectroscopy and attenuated total reflection sampling have been used to detect adulteration of single strength apple juice samples. The sample set comprised 224 authentic apple juices and 480 adulterated samples. Adulterants used included partially inverted cane syrup (PICS), beet sucrose (BS), high fructose corn syrup (HFCS), and a synthetic solution of fructose, glucose, and sucrose (FGS). Adulteration was carried out on individual apple juice samples at levels of 10, 20, 30, and 40% w/w. Spectral data were compressed by principal component analysis and analyzed using k-nearest neighbors and partial least squares regression techniques. Prediction results for the best classification models achieved an overall (authentic plus adulterated) correct classification rate of 96.5, 93.9, 92.2, and 82.4% for PICS, BS, HFCS, and FGS adulterants, respectively. This method shows promise as a rapid screening technique for the detection of a broad range of potential adulterants in apple juice.     

Adulteration of apple with pear juice: emphasis on major carbohydrates, proline, and arbutin

Detection of juice-to-juice adulteration based on chemical composition studies is a common method used by government regulatory agencies and food companies. This study investigated the use of major carbohydrate (fructose, glucose and sucrose), polyol (sorbitol), proline, and phenolic profiles as indicators of pear adulteration of apple juice (PAAJ). For this work, a total of 105 authentic apple juice samples from 13 countries and 27 authentic pear juice samples from 5 countries were analyzed. Because the major carbohydrate ranges for these juices showed significant overlap their use as markers for PAAJ detection would be very limited. It was found that sorbitol and proline means for apple and pear were significantly different; however, their broad natural ranges would afford PAAJ at levels up to 30% without detection. In addition, careful selection of the pear juice used as the adulterant would further limit the usefulness of these markers for PAAJ detection. Arbutin was conclusively identified as a marker for pear juice on the basis of its presence in all 27 authentic pear samples and its absence (<0.5 microg/mL) in all 105 apple juice samples analyzed in this study. The application of the developed HPLC-PDA method for arbutin analysis to detect PAAJ at levels as low as 2% (v/v) was demonstrated. A confirmation method for the presence of arbutin in pure pear juice and apple adulterated with pear juice was introduced on the basis of the hydrolysis of arbutin to hydroquinone employing beta-glucosidase, with reactant and product monitoring by HPLC-PDA.     

Composition of apple juice

Thirty-one samples from 8 geographic growing regions of the United States and 15 varieties common to these areas were converted to apple juice and analyzed for their attributes over the 3 year period 1979, 1980, and 1981. The total of 93 samples were analyzed for ash, brix, pH, proline, specific gravity, total acid, sorbitol, sucrose, fructose, and glucose. The elements cadmium, calcium, iron, lead, phosphorus, potassium, sodium, and zinc were also determined. These data are presented to serve as a data base for the detection of fraudulent or adulterated apple juice.     

Characterization of paprika (Capsicum annuum) extract in orange juices by liquid chromatography of carotenoid profiles.

The carotenoid pigment profiles of authentic pure orange juices from Spain and Florida and an industrial paprika (Capsicum annuum) extract used for food coloring were obtained using reversed-phase liquid chromatography with a C18 packed column and an acetone/methanol/water eluent system. The procedure involving the carotenoid extraction is described. Both retention times and spectral properties using photodiode array detection for characterization of the major carotenoids at 430 and 519 nm are given. The influence of external addition of tangerine juice and/or paprika extract on orange juice color is described using the U.S. Department of Agriculture scale and adulterated orange juice. The procedure for quantitation of externally added paprika extract to orange juice is investigated, and the limit of quantitation, coefficient of variation, and recoveries are determined.     

Liquid chromatographic methodology for the characterization of orange juice

Liquid chromatographic (LC) methodology potentially useful for the characterization of orange juice, with particular regard to detecting adulteration of orange juice by computer pattern recognition analysis, has been developed. After dilution with methanol the juice is extracted with hexane to remove the carotenoids, which are chromatographed on a C18 column with an acetonitrile-methanol-methylene chloride mobile phase and detection at 450 nm. Further extraction of the juice with methylene chloride isolates the methoxylated flavones, which are chromatographed by reverse phase LC with an acetonitrile-methanol-water mobile phase and detection at 280 nm. The flavanone glycosides remaining in solution are chromatographed on a C18 column with an acetonitrile-water mobile phase and detection at 280 nm. The precisions of the heights of the 32 LC peaks selected for pattern recognition analysis were determined from 5 replicate analyses of a single juice. Coefficients of variation of the replicates ranged from 0.3 to 4.5%, with an average of 2.1%. Adulteration of products with sodium benzoate-fortified pulpwash or grapefruit juice can be detected by this method. Pattern recognition analysis of the data obtained for 80 authentic and 19 adulterated orange juices showed that the method is potentially useful for distinguishing between authentic and adulterated products.     

How to improve bayberry (Myrica rubra Sieb. et Zucc.) juice color quality: effect of juice processing on bayberry anthocyanins and polyphenolics

Fresh bayberries (Myrica rubra Sieb. et Zucc.) were processed into juice at an industrialized scale with four treatments: control, SO2 addition, pasteurization of the crushed pulp, and blanching before fruit crushing. Changes in anthocyanin pigments and polyphenolics (hydrobenzoic acids and flavonol glycosides) were monitored during processing. Centrifuged juice yield ranged from 73 to 78% (w/w), but only 12-27% of the anthocyanins and 20-32% of the polyphenolics were recovered in the ultrahigh-temperature (UHT) juices. Fifty-two to 58% of anthocyanins and 30-35% of polyphenolics were present in the centrifuged cakes. The initial processing steps of blanching, crushing, pasteurization, and depectinization caused a great loss of total and individual polyphenolics. Total monomeric anthocyanins were significantly higher (p < 0.05) in pasteurization- and blanching-treated samples than those in the SO2 treated samples, whereas those in the SO2-treated sample were significantly higher (p < 0.05) than those in the control juice. Overall polyphenolic levels were significantly higher (p < 0.05) in pasteurization- and blanching-treated samples than in the SO2-treated and control samples after each processing step. Important changes occurred in the polyphenolic profile with a 50-150% of hydroxybenzoic acids increase due to the free gallic acid from the flavonol glycoside-gallates during the initial processing steps. Flavonol deoxyhexosides were more stable than the flavonol hexosides during bayberry juice processing.     

Stable isotopic carbon composition of apples and their subfractions--juice, seeds, sugars, and nonvolatile acids

The 13C:12C ratios of 8 authentic apple juice samples and their subfractions were determined by mass spectrometry. Apples from Argentina, Mexico, New Zealand, and the United States were processed into juice; pulp was collected from the milled fruit and seeds were collected from the press-cake. Sugars, nonvolatile acids, and phenolics were isolated from the juice by treatment with ion-exchange resins and polyvinylpyrrolidone (PVPP). The mean value for all juice samples was -24.2% which is close to the values reported by other investigators. Juice from apples grown in Argentina, Mexico, and New Zealand did not differ from U.S. samples. The isotopic composition of the subfractions ranged from -22.0 to -31.0%. The values for the pulp were essentially the same as for juice. The sugar fraction was slightly less negative than the juice; the nonvolatile acid and phenolic fractions were more negative. The levels of nonvolatile acids and phenolics in apple juice are low, however, so these compounds contribute little to overall delta 13C values in juice.     

Characterization of cider apples on the basis of their fatty acid profiles

In the current study, the fatty acids composition of 30 monovarietal apple juices from six cider apple varieties belonging to two categories was analyzed. The different apple juices were obtained from three consecutive harvests (1997, 1998, and 1999). The fatty acids concentration in apple juice together with chemometric techniques such as principal components analysis (PCA), soft independent modeling of class analogy (SIMCA), and linear discriminant analysis (LDA), allowed us to differentiate apple juices on the basis of the sweet or sharp category to which the cider apple variety belongs. Fatty acids such as the unsaturated oleic and linoleic acids, and saturated caprylic, capric, stearic, and palmitic acids were related to the sweet cider apple category, while pentadecanoic acid is related to the sharp class.     

Physiological effects of extraction juices from apple, grape, and red beet pomaces in rats

In comparison to classical fruit juice processing, polyphenols and dietary fiber can be extracted from pomace by means of pectinases and cellulases. In the present study, rats were fed with such produced extraction juices from apples, grapes, and red beets as drinking fluids instead of water for 4 weeks to evaluate their physiological effects. In all test groups, the intake of extraction juices was greater as compared to control (water intake), resulting in a higher urine excretion. In the apple and grape group, pH values in feces was lower than control. Administration of extraction juices from apples increased fecal counts of Lactobacillus and Bifidobacterium. More acetate and total short-chain fatty acids appeared in intestinal contents of the apple and red beet group. Furthermore, the intestinal contents of test groups contained higher concentrations of primary bile acids, cholesterol, and cholesterol metabolites but lower concentrations of secondary bile acids. The total amount of steroids excreted by these groups was also greater than control. Quercetin and isorhamnetin appeared in urine of rats fed extraction juices from apples and grapes; in urine of the former group, phloretin was found also. Administration of the extraction juices, enriched in secondary plant metabolites and dietary fiber, resulted in beneficial nutritional effects in rats.