Prediction of chemical,physical and sensory data from process parameters for frozen cod using multivariate analysis

Physical, chemical and sensory quality parameters were determined for 115 cod (Gadus morhua) samples stored under varying frozen storage conditions. Five different process parameters (period of frozen storage, frozen storage temperature, place of catch, season for catching and state of rigor) were varied systematically at two levels. The data obtained were evaluated using the multivariate methods, principal component analysis (PCA) and partial least squares (PLS) regression. The PCA models were used to identify which process parameters were actually most important for the quality of the frozen cod. PLS models that were able to predict the physical, chemical and sensory quality parameters from the process parameters of the frozen raw material were generated. The prediction abilities of the PLS models were good enough to give reasonable results even when the process parameters were characterised by ones and zeroes only. These results illustrate the application of multivariate analysis as an effective strategy for improving the quality of frozen fish products. © 1998 Society of Chemical Industry.     

Changes in aroma quality of ‘Golden Delicious’ apples after storage at different oxygen and carbon dioxide concentrations

‘Golden Delicious’ apples were stored in semicommercial chambers in normal atmosphere and in various controlled atmospheres (CAs) in which oxygen and carbon dioxide contents were held at 10, 20 or 30 l m⁻³ for 3, 5 or 7 months. Following storage, fruits were kept at 20 °C for 1, 5 or 10 days, after which quality parameters were determined and aroma components were obtained and analysed by the dynamic headspace method and quantified by gas chromatography–mass spectrometry. The highest emission of volatile components was obtained after 5 months of storage. Esters were the main compounds released after cold storage in all conditions. Normal cold storage gave the highest amounts of straight‐chain esters, while low‐oxygen atmospheres gave the highest amounts of branched‐chain esters. After 3 and 7 months there were no significant differences in volatiles on comparing fruits from different storage conditions. Low‐oxygen atmospheres had beneficial effects on fruit firmness, titratable acidity and colour. Apples coming from low‐oxygen atmospheres gave the highest sensory score after 5 months of cold storage. © 2000 Society of Chemical Industry     

烟丝挥发性香味物质与卷烟感官质量的相关性研究

选取中国市场价为每条200～300元的卷烟(30个样品)为研究对象,采用同时蒸馏萃取法测定其挥发性香味物质含量,并对其感官质量进行评价。运用简单相关分析、逐步回归分析和主成分分析对各项指标间的相关性进行了统计分析。结果表明:不同卷烟烟丝中的总香味含量,各类香味物质和感官评价结果符合正态分布;不同卷烟烟丝中致香成分和感官质量之间具有一定的相关性,其中,卷烟香气和杂气与烟丝所含的总香味物质以及大部分香味物质呈显著正相关。得到香气和谐调性指标的预测模型方程,经显著性测验均达到了极显著水平。总香味物质含量、新植二烯、酮类、醛类和酚类是主要的影响因子,其中,总香味物质含量是影响卷烟感官质量的主体因子。     

Effect of controlled atmospheres and shelf life period on concentrations of volatile substances released by ‘Pink Lady®’ apples and on consumer acceptance

BACKGROUND: ‘Pink Lady^®’ (Malus × domestica Borkh.) apples were harvested at commercial maturity and stored at 1 °C under either air or controlled atmosphere (CA) conditions (2.5 kPa O₂: 3 kPa CO₂ and 1 kPa O₂: 2 kPa CO₂) for 15 or 28 weeks. Standard quality parameters, consumer acceptance and volatile compound emission were evaluated after cold storage plus shelf life period at 20 °C. RESULTS: A shelf life period of 17 days after long‐term storage in controlled atmosphere allowed the regeneration of the characteristic esters associated to the aroma of this variety. Sixty‐five per cent of consumers preferred apples with higher emissions of aroma‐active volatile compounds, despite the fact that these apples displayed lower values for standard quality attributes. The most accepted samples corresponded to fruit stored in air for 15 weeks regardless of post‐storage period, in air for 28 weeks plus 1 day at 20 °C, and in 2.5 kPa O₂: 3 kPa CO₂ for 15 weeks plus 7 days at 20 °C. CONCLUSIONS: Concentrations of specific aroma volatile compounds are suggested to be more important than total aroma emission for consumer acceptance of ‘Pink Lady^®’ apples. Copyright © 2009 Society of Chemical Industry     

Relationships between volatile composition and sensory evaluation in eight varieties of netted muskmelon (Cucumis melo L var reticulatus Naud)

The quality parameter of muskmelon (Cucumis melo L var reticulatus Naud) is often identified with the sugar content, particularly sucrose. However, high soluble solids concentration at harvest does not always correspond with high overall fruit quality and should be used in conjunction with the evaluation of aroma. In order to find quality indices, correlations were checked between aroma compounds detected on the melon pulp by headspace gas chromatography and sensory evaluation. Eight cultivars of muskmelon were analysed for their aroma content and other quality parameters. Aroma compounds were mainly esters, while (Z)‐6‐nonenal and (E)‐6‐nonenol, characteristic of melon, were not detected with the technique used. The data were subjected to statistical analyses in order to find significant correlations. High values of correlation were not found between chromatographic and sensory data, but a high correlation was found between total aromas and ethyl esters, both data of analytical source. This fact means that ethyl esters could be very important compounds for melon flavour and could be considered as markers of a good‐quality aroma. © 2002 Society of Chemical Industry     

Physicochemical and sensory analysis of dry bean landraces in conjunction with multivariate analysis: an exploratory approach

Five landraces of Greek common dry bean (Phaseolus vulgaris L.), were analysed for thirteen physico‐chemical and eighteen sensory variables. Brightness, acceptance, odour and hardness were the most important sensory variables for the overall acceptability of the cooked product. Application of principal component analysis revealed a rather weak relationship between the sensory attributes and the physico‐chemical variables. However, a certain grouping of cultivars with corresponding properties [(PC1 vs. PC2, Kastoria with saltiness, hardness, grassiness, intensity, protein and metal; Byzitsa bushy with fat, odour and sourness; Ksanthi and Belestino with tenaciousness, chroma, pH and overall impression), (PC1 vs. PC3 Byzitsa bushy with odour and acridness; Ksanthi with metal, hardness and pH; Kastoria with colour, protein and intensity)] was made. On the contrary, cluster analysis showed a much more satisfactory grouping of dry bean varieties based on their geographical origin. The multiple regression equation explained 72.3% of the variation in total acceptance of dry beans. The relative importance of brightness, acceptance, smell and hardness in predicting the overall impression of dry beans was 13%, 13.7%, 26% and 10%, respectively. These results may indicate that smell, brightness and acceptance are the most important factors determining dry bean total acceptability, so effort should be directed at improving these attributes in an attempt to satisfy consumer experience.     

气相色谱-离子迁移谱法结合多元统计学分析不同陈酿时间白兰地的挥发性香气成分差异

目的 利用气相色谱-离子迁移谱（gas chromatography-ion mobility spectrometry, GC-IMS）结合化学计量学方法判别不同年份白兰地的差异,建立桶藏白兰地年份酒快速判别预测模型。 方法 基于GC-IMS技术,利用指纹图谱判别各年份白兰地差异和特征性挥发性物质,结合化学计量学方法对各物质吸收峰体积进行数据降维并且建立年份判别模型。 结果 共定性出50种挥发性风味物质,由指纹图谱可判断不同年份白兰地中VOCs含量及种类存在显著差异。利用多元统计方法对鉴定出的香味物质吸收峰数据进行降维分析和可视化操作,主成分分析（principal component analysis, PCA）累计贡献率可达85%,表明不同年份样品具有良好的聚类效果。通过偏最小二乘回归分析（partial least squares-discriminant analysis, PLS-DA）建立年份酒判别模型,得到不同年份酒样的特征性标记物,筛选出22种VIP值大于1的对陈酿白兰地年份判别贡献较大的香气成分。 结论 利用GC-IMS结合多元统计分析可判别年份白兰地中特征性呈味物质种类和含量差异并且建模效果良好,得到研究结果可为白兰地的年份鉴别和质量控制提供经验借鉴和应用思路。     

不同产地库尔勒香梨生育期果实品质变化规律及综合评价

目的 分析库尔勒香梨果实外观品质与营养品质的时空变化规律,比较果实品质的区域差异,对不同产地商品果的品质进行综合评价。方法 采集花后60d~140d内不同产区（新疆库尔勒、阿克苏、甘肃酒泉）的10个果园共计90份库尔勒香梨样品,用常规方法测定单果重、纵径、横径等外观品质指标,通过直接滴定法测定还原糖和总酸的含量,用高效液相色谱法分析果实中的柠檬酸、苹果酸、酒石酸、富马酸、丁二酸和山梨糖醇、果糖、葡萄糖、蔗糖,采用方差分析比较生育期产地的品质差异,通过主成分分析法综合评价果实的品质优劣。结果 库尔勒香梨果实在花后60~140d,随着果实的不断成熟,硬度呈快速下降的趋势,由7.19 N/cm2下降至2.91 N/cm2。还原糖的含量由1.1g/100g上升到7.3g/100g,总酸由3.63g/kg下降到0.71g/kg。成熟期4种糖中果糖、葡萄糖、山梨糖醇占比为99%,5种有机酸中苹果酸和酒石酸占比为96%。果糖∶葡萄糖∶山梨糖醇含量比值由花后60d时的1∶1.5∶7.5上升为花后140d的1∶0.9∶0.6,苹果酸∶酒石酸∶柠檬酸含量比值由花后60d时的1∶0.37∶0.03变化为花后140d的1∶0.27∶0.13,糖酸比由花后60d的24上升到花后140d的174。成熟期三个产地糖类含量无显著差异,横径、果形指数、柠檬酸新疆与甘肃产地存在显著差异（P＜0.05）。主成分分析结果表明,前四个主成分累计方差贡献率为89.14%,果形指数、果糖、横径、山梨糖醇、葡萄糖、苹果酸、总酸可作为库尔勒香梨品质评价的重要指标。结论 库尔勒香梨在花后60d~140d的生育期内,果实中山梨糖醇的比例随着成熟度的增加逐渐降低,果糖和葡萄糖比例显著增加,有机酸以苹果酸和酒石酸为主,呈显著下降趋势,花后140d糖酸比最大,风味最好。在采样果园中库尔勒4个果园的品质最好,酒泉3个果园次之,阿克苏3个果园品质较差。     

Implementation of quality control methods (physico-chemical, microbiological and sensory) in conjunction with multivariate analysis towards fish authenticity

Nowadays authenticity of foods and fish in particular has become of crucial importance because of high number of adulteration cases. Authenticity control has gained ground thanks to the development of several rapid physico‐chemical and microbiological methods aiming at distinguishing one species from another based on solid scientific evidence. It has been proven that despite the precision and accuracy of robust analytical and protein and DNA‐based techniques, detection of authenticity could not be claimed without resorting to multivariate analysis. This review summarizes both the most advanced and state of the art used techniques for detecting fish and seafood authenticity (both in terms of species and geographical origin). Another issue reported in this review is the preservation of fish and seafood through the implementation of old and novel techniques (ice, modified atmosphere packaging). Several informative tables were included in this paper referring to the employed quality control and sensory analysis methods and multivariate analysis for fish and seafood.     

Non-destructive evaluation of maturity and quality parameters of pomegranate fruit by visible/near infrared spectroscopy

In this study, the potential of visible and near infrared spectroscopy was investigated to classify the maturity stage and to predict the quality attributes of pomegranate variety “Ashraf” such as total soluble solids content, pH, and titratable acidity during four distinct maturity stages between 88 and 143 days after full bloom. Principal component analysis was used to distinguish among different maturities. The prediction models of internal quality attributes of the pomegranate were developed by partial least squares regression. The transmission spectra of pomegranate were obtained in the wavelength range from 400 to 1100 nm. In this research several preprocessing methods were utilized including centering, smoothing (Savitzky–Golay algorithm, median filter), normalization (multiplicative scatter correction and standard normal variate) and differentiation (first derivative and second derivative). It concluded that different preprocessing techniques had effects on the classification performance of the model using the principal component analysis method. In general, standard normal variate and multiplicative scatter correction gave better results than the other pretreatments. The correlation coefficients (r), root mean square error of calibration and ratio performance deviation for the calibration models were calculated: r = 0.93, root mean square error of calibration = 0.22 °Brix and ratio performance deviation = 6.4 °Brix for total soluble solids; r = 0.84, root mean square error of calibration = 0.064 and ratio performance deviation = 4.95 for pH; r = 0.94, root mean square error of calibration = 0.25 and ratio performance deviation = 5.35 for titratable acidity.     

云南不同产地玛咖挥发油成分的GC-MS检测及多元统计分析

为研究云南玛咖挥发油成分,对云南具有代表性的八个玛咖种植区样品采用同时蒸馏萃取法提取挥发油,利用气相色谱-质谱联用技术对所得挥发油进行分离鉴定,应用相似度评价、聚类分析和主成分分析等多元统计方法进行分析,结果鉴定出挥发油成分59种,其中共有成分39种,这些共有成分总含量在各地玛咖样品挥发油总量中占比都超过99%。含量较高的共有成分有:异硫氰酸苄酯、苯乙腈、4-甲氧基苄基异硫氰酸酯、3-甲氧基苯乙腈、棕榈酸、9,12,15-十八碳三烯酸、苯甲醛、9,12-亚油酸、9,12,15-十八碳三烯酸乙酯、亚油酸乙酯。云南八个玛咖种植区样品挥发油成分相似,但由于含量差别而呈现出具有明显差异的两个类别。      

中国进口红葡萄酒香气特征与价格之间的关联分析

葡萄酒样本选择673 款不同价格水平的进口干红葡萄酒。葡萄酒的香气特征采用经过培训的品尝员的感官描述分析得到,而后香气特征采用“葡萄酒香气轮”上的香气标准术语归类。供试葡萄酒香气特征被标准化后被分为12 个香气类别,每一香气特征和香气类别在不同价格区段的出现频率经统计计算得到。结果表明：不同价格区段的进口葡萄酒具有的香气特征有差异,除了＞1 400 元/瓶的葡萄酒之外,其余价格区段的葡萄酒香气特征的出现频率与价格水平之间存在多元线性关系。偏最小二乘回归模型确认了进口干红葡萄酒价格与香气特征之间的数学联系,即来源于陈酿中的香气特征与价格呈正相关,并且确认＞1 400 元/瓶的进口葡萄酒产品属于奢侈品的特例。     

Impact of different temperature abuse scenarios on sensory quality and off-odour formation in ready-to-eat salad leaves

Packages of ready-to-eat (RTE) wild rocket and lettuce baby leaves were subjected during 8 days of cold storage to a chronic temperature abuse (CTA) at sub-optimal storage temperature (10 °C) or to a short-term (6 h) abuse at ambient temperature (STA) to evaluate the impact of two temperature abuse scenarios on gas composition within the packages, leaf sensory quality and volatile organic compounds (VOCs). In both species, the CTA scenario had a markedly higher impact on gas composition, sensory quality and off-odour formation than the STA, and the limit of sensory acceptability was reached in the CTA scenario 4 days or more earlier than in the STA. Sulphur compounds were the main responsible for off-odour perception in both leafy salads. Results from the present study may be useful in the assessment of critical points in the cold chain of RTE fresh produce and in prioritising actions towards improved cold-chain management.     

Water retention properties and solubility of the myofibrillar proteins: Interrelationships and possible value as indicators of the gel strength in cod surimi by a multivariate data analysis

The quality of surimi made from fish aged on ice for up to 14 days was evaluated by compression test on a model product. Water holding capacity (WHC) and pH in the fish mince, and protein content, pH, salt solubility of the myofibrillar proteins and hydration index of the insoluble proteins (HUP) in the surimi, were determined. Their interrelationships and utility as indicators of surimi quality were evaluated by a multivariate data analysis. The main tendencies of variation among the chemical parameters were examined by the use of principal component analysis. Correlations between the chemical parameters (X-variables) and the gel strength of surimis (Y-variable) were studied by the use of partial least squares regression. Age of the raw material and protein content of the surimi seemed to be the main determinants of the gel strength. Among the remaining variables only HIIP showed a potential value as indicator of the gel strength. WHC and HIIP seemed to reflect two different water retention properties of the proteins.     

基于GC-IMS技术的不同产地青钱柳茶挥发性成分表征及分析

目的：研究不同产地青钱柳茶挥发性气味物质差异。方法：以湖南常德、湖南张家界、湖南邵阳、江西修水、贵州黔东南、湖北恩施的青钱柳茶为研究对象,采用气相色谱—离子迁移谱联用（GC-IMS）技术并结合偏最小二乘判别分析（PLS-DA）,探讨不同产地青钱柳茶中特征差异挥发性物质及其相似度。结果：不同产地青钱柳茶共检测出120种挥发性有机物,包括部分物质的单体及其多聚体,分别为醛类34种、烯烃类21种、醇类19种、酮类16种、酯类10种、羧酸类8种、呋喃类5种、吡嗪类4种、醚类2种及苯系物1种。其中γ-松油烯、苯乙烯、4-甲基-1-戊醇、正辛醛为主要特征差异挥发性物质。结论：不同产地间青钱柳茶挥发性有机物质均存在一定差异（P＜0.05）,GC-IMS技术可有效实现青钱柳茶的产地鉴别和质量控制。