Chemical, physical, and sensorial characteristics of "Terrincho" ewe cheese: changes during ripening and intravarietal comparison

The objectives of this study were to monitor the changes in chemical [moisture, acidity, pH, and water activity (a(w))] and physical (color and texture) parameters of "Terrincho" ewe cheese during 60 d of ripening, and to determine the correlations between the changes in instrumental texture and color parameters and the ripening time of the product. Intravarietal comparison of Terrincho ewe cheese from 5 different dairy plants was performed by evaluation of mechanical parameters from texture profile analysis (TPA) and color parameters in terms of CIELAB color space (L*, a*, and b*). In addition to mechanical and color tests, composition analyses and sensory tests were performed. The results were evaluated with statistical methods (single valued and multivariate analysis). During the first 20 d of ripening, an increase in hardness, fracturability, gumminess, chewiness, and yellowness occurred. Simultaneously, adhesiveness, resilience, L* (inside cheese, "i" and external "e"), and cohesiveness decreased. After 20 d of ripening hardness, fracturability, gumminess, and chewiness decreased and cohesiveness increased. The ripening time of Terrincho cheeses can be estimated with 6 variables: L* (external, e), L* (i), b* (inside cheese, i), hardness, a* (i), chewiness, and a constant. The estimation error was 4.2 d. Evaluation of composition, pH, texture profile analyses, color, and related sensory characteristics of Terrincho cheeses from 5 different dairy plants (with 30 d of ripening) revealed correlations between these parameters.     

Postharvest Ripening Characterization of Greenhouse Tomatoes

The determination of °Brix, pH, titratable acidity and antioxidant composition such as β-carotene, lycopene, and vitamin C was done in greenhouse “Savoura” tomatoes during maturation. The chromatic values L*, a*, b* were determined at the top surface of the tomato, and its strength-deformation curve was tested with a texturometer. Results pointed out that °Brix and titratable acidity did not change during postharvest, while β-carotene, lycopene, and vitamin C contents increased continuously toward the red stage of tomato. The colour values L*, a*, b*, and ratio a*/b* had a good correlation with the maturity stages. Also, a high correlation between lycopene content and (a*/b*) ratio was found, which was well represented with a second order polynomial function (r² = 0.95). This equation permits to appropriately estimate lycopene content of tomato as a function of its color, without any chemical analysis. During ripening, tomato texture changed from firm turgid to soft and the puncture deformation degree increased. Tomato firmness and chromatic values had a good correlation, and the lycopene content was a logarithm function of firmness (r² = 0.81). The strength in puncture test increased linearly with deformation until the bioyield point. The measured force was analyzed as the sum of the compression and the shear forces. The two force coefficients can be considered as tomato properties, independent of the puncture probe. These coefficients were found to decrease during tomato maturation.     

Physicochemical characteristics of Spanish-type dry-cured sausage

The colour and physicochemical parameters of Spanish-type dry-cured sausage during fermentation and ripening were evaluated. The CIE L*, a*, b* and pH, moisture content, lactic acid concentration and residual nitrite level were measured in two different zones (centre and peryphery). Sausage processing had two stages, fermentation and ripening. Lightness (L*) was the only colour parameter whose development (during the ripening stage) was dependent on the zone studied, in this case becoming lighter in the center zone. Redness (a*) increased during the fermentation stage and decreased during ripening, while the yellowness (b*) decreased throughout the process. The development of pH, lactic acid and residual nitrite levels were non related to the zone studied during both the fermentation and ripening stage.     

Color and Texture Change Kinetics in Ripening Bananas

Kinetics of color and texture changes in ripening bananas were investigated as a function of storage temperature (10, 16, 22, 28 °C). Color was evaluated in terms of L, a and b values as well as the total color difference (ΔE) representing the residual deviations from the ripe stage. Puncture force (PF) was used to evaluate the texture properties of banana. The results indicated that the time dependence of L, ΔE and PF values followed a logistic model, while a and b values were well described by a simple zero-order and fraction conversion models, respectively. The Arrhenius equation adequately described the temperature dependence of the reaction rate constants for both color and texture parameters, from which the activation energies and rate constant at reference temperature 15 °C were obtained. There were significant linear correlations between color parameters (L, a, b, ΔE) and texture parameter (PF).     

Lutein Is Stable in Strawberry Yogurt and Does Not Affect its Characteristics

ABSTRACT:  The impact of various levels of lutein on the physicochemical, microbiological, and sensory characteristics of yogurt over its shelf life was determined. Nonfat strawberry yogurts were prepared with 0, 0.5, 1.5, and 3.0 mg lutein per 170 g serving (20% overages were included to account for processing losses). The lutein was incorporated prior to homogenization of the yogurt mix. Stability of lutein, viscosity, pH, syneresis, standard plate counts, coliform counts, color (L*, a*, b*), and sensory evaluation (flavor, body and texture, and appearance and color) were measured at weeks 0, 1, 3, and 5 after product manufacture. The interaction effect between levels of lutein and storage time was significant for a* (redness-greenness) values. Lutein levels remained above target throughout the 5-wk storage study. Lutein did not affect viscosity, pH, syneresis, L* (lightness) and b* (yellowness-blueness) values, standard plate counts, coliform counts, flavor, body, texture, appearance, and color scores. These results suggested that lutein was suitable for inclusion in functional yogurts. The skin and eye health benefits provided by lutein can easily be incorporated into yogurt to complement inherent nutritional properties.     

不同条件对‘巴西蕉’和‘南天黄’香蕉后熟的影响

‘南天黄’为性状优良且抗枯萎病的香蕉新品种,其后熟条件与传统栽培品种‘巴西蕉’不同,然而生产中常以统一做法对‘南天黄’进行催熟,易造成生产误判。为提高香蕉品质,延长货架期,本研究以500 mg/L乙烯利喷雾处理后的‘南天黄’与‘巴西蕉’果实为材料,实验分为（22±2）℃处理组（T2）、（22±2）℃＋双向拉伸聚丙烯（biaxially oriented polypropylene,BOPP）薄膜包装处理组（T-2）、17 ℃处理组（T1）、17 ℃＋BOPP薄膜包装处理组（T-1）,观察果皮色差、果肉硬度、果实质量损失率、可溶性固形物质量分数的变化和货架期的特点,以此制定‘南天黄’合理催熟方案。T1、T-1处理组‘南天黄’褪绿转黄（催熟时间）比‘巴西蕉’早1 d,T1处理组‘南天黄’比‘巴西蕉’货架期长2 d;T2处理组‘南天黄’褪绿转黄比‘巴西蕉’迟1 d,货架期长2 d;与T2处理组相比,T1处理组香蕉后熟末期硬度、色差L*值、C*值、a*值更大,货架期长2 d,但后熟后颜色不如T2处理组的鲜黄;BOPP包装延缓了褪绿转黄,使催熟时间延长4 d,货架期缩短。因此前期高温（21 ℃）后期低温（17 ℃）是‘南天黄’获得较好的货架品质和货架期的后熟条件。     

密集烘烤过程中烤烟上部叶质地和色度变化研究

研究上部烟叶叶片、主脉在密集烘烤中质地和色度随干湿球温度变化的规律,为烘烤工艺的优化和完善提供理论依据。分别应用质构仪质地分析试验法和色差计研究了烘烤中烟叶硬度、回复性、粘聚性、咀嚼性4个质地参数和L*、a*、b*三个色度参数及水分的变化情况。结果表明:烘烤中烟叶叶片质地和色度各参数在变黄期38℃前后发生了明显的变化;主脉各参数主要在42℃之后,尤其是48~54℃。烘烤中烟叶TPA(texture profile analysis)测试评价参数硬度、回复性、咀嚼性曲线图的动态变化更为直观。烘烤中烟叶色度各参数差异性均极显著（P<0.01）,且a*值差异显著性好于b*值;叶片色度的差异显著性比主脉的更直观。相关分析表明,烘烤中烟叶叶片TPA测试参数硬度、粘聚性、咀嚼性的相关性较好（0.952~0.992）,是评价烟叶质地变化的可靠性指标;粘聚性和回复性可以灵敏地反映烟叶主脉的质地变化。相对于主脉,叶片色度的各参数的相关性更好（0.852~0.962）,呈显著或极显著正相关。色度各参数的相关分析表明,L*与a*的相关性明显好于L*与b*的相关性。      

蒙顶黄芽不同加工工序中色泽变化与品质相关性研究

研究不同加工工序制成的蒙顶黄芽干茶、汤色及叶底色泽,并进行色素成分检测及品质审评,分析干茶、汤色及叶底色泽L*a*b*值与各审评因子得分、色素含量、品质总分的相关性,为黄茶闷黄程度及色泽的评价提供一定的参考依据。以蒙顶黄芽加工过程中的茶样为试验材料,采用色彩色差计CR410测定干茶、汤色及叶底的L*a*b*值,再与干茶、汤色、叶底得分做显著性分析,与茶色素、叶绿素及品质总分做相关性分析。结果表明,干茶L*、a*、b*值与干茶色泽审评得分呈显著或极显著相关（P<0.05, P<0.01）,茶汤L*、a*、b*值与汤色审评得分均呈极显著相关（P<0.01）,其相关系数分别为?0.93、0.97、0.93,叶底L*、a*、b*值与叶底得分均呈极显著相关（P<0.01）,其相关系数分别为?0.96、0.97、0.98;干茶、汤色及叶底的L值与茶色素含量呈极显著负相关（P<0.01）,a*、b*值与茶色素含量呈极显著正相关（P<0.01）;干茶、汤色及叶底的L*值与叶绿素含量呈极显著正相关（P<0.01）,a*、b*值与叶绿素含量呈极显著负相关（P<0.01）。蒙顶黄芽感官品质与L*、a*、b*值及色素之间的相关性表现为:与干茶 L *值、汤色L *值、叶底L *值、叶绿素a*、叶绿素b*含量均呈极显著负相关（P<0.01）,与干茶a*b*值、汤色a*b*值、叶底 a*b*值及茶色素含量均呈显著或极显著正相关（P<0.05, P<0.01）,除干茶a*值外,相关系数均在0.80以上。本试验表明,就各审评因子及品质总分而言,采用色泽Lab值测定方法可为黄茶色泽与品质相关性研究提供一定的理论基础。     

烤烟表面颜色的量化及其与胡萝卜素类物质的关系

为揭示我国不同产区烤烟颜色特征差异的成因,采用L*a*b*均匀颜色空间的颜色表征方法对我国11个省60个产烟县的C3F烟叶进行了测量分析,并研究了烤烟颜色的色空间分布指标与类胡萝卜素含量的关系。结果表明:①我国不同产区烤烟颜色的色空间指标明度L*、红度a*、黄度b*、色饱和度c*及类胡萝卜素类物质差异明显,东南烟区烟叶的明度、黄度和色饱和度较低,红度较高,类胡萝卜素含量较低,叶黄素比例较高;长江中上游和西南烟区烟叶的明度、黄度和色饱和度较高,红度相对较低,类胡萝卜素含量较高;北方烟区烟叶的明度相对较高,色饱和度相对较低,类胡萝卜素含量较低。②烤烟类胡萝卜素类物质与颜色色空间分布指标关系密切,随类胡萝卜素含量的提高,红度、黄度、色饱和度等指标均呈现出显著上升趋势,明黄度比值呈显著下降趋势。     

冷却猪肉新鲜度的色差快速分析评价方法

为了得到冷却猪肉新鲜度的变化规律,本研究以冷却猪肉里脊部分为研究对象,进行球蛋白沉淀实验、感官评价、pH值、水分含量、肉浸液以及肌肉表面颜色值测定。结果表明：球蛋白沉淀实验、pH值能够较好地反应肉品新鲜度的变化,色差分析符合一定的规律：肌肉表面色差测定中,20℃条件下,a*变化与贮藏时间显著相关(P＜0.05),L*变化显著(P＜0.05);4℃条件下,b*、C变化与贮藏时间极显著相关(P＜0.01),L*值与pH值极显著相关(P＜0.01);对于肉浸液,L*、b*、C、ΔE*均发生显著性变化(P＜0.05),20℃条件下L*、b*、C、ΔE*与贮藏时间和pH值显著相关(P＜0.05),而4℃条件下,L*、C、ΔE*与贮藏时间显著相关(P＜0.05),L*、a*、b*、C、ΔE*值与pH值极显著相关(P＜0.01);冷链过程中,当L*高于48.73、a*高于4.72、b*高于9.18时可认定冷却肉为新鲜肉。     

OBJECTIVE COLOR MEASUREMENT OF FRESH DATE FRUITS AND PROCESSED DATE PRODUCTS

Because of significant international trade in date fruits, the need for objective color measurement for maintaining strict quality standards has become obvious. The results on color measurement of specimens of fresh date fruits at four stages of maturity and some processed date products in terms of CIE L*a*b* color coordinate values and hue angle (η) are presented. The L*, a*, b* and η values were found to indicate the color of date fruits and processed date products objectively. Measurements utilizing a Macbeth Color Checker spectrophotometer may, therefore, be extremely useful in quantifying the color of date fruits for objective color comparison between different date cultivars and for quality control of processed date products in the international trade.     

Changes in color parameters of corn kernels during roasting

Changes in color parameters (L*, a*, b*, ΔE*, h°, and C* values) of corn during roasting were investigated and subsequently described using mathematical models. Corn kernels were roasted for 50 min at 160, 180, 200, 220, and 240°C. The L*, b*, h°, and C* values tended to decrease more rapidly as the roasting temperature and time increased up to 220°C and 50 min, whereas a* and ΔE* values tended to increase. Variation of L* and ΔE* values was found to be proportional to the roasting temperature and time. Variation of L* value during roasting above 180°C was adequately described by a first-order model. Cubic model satisfactorily described changes in all of color parameters over the temperature range. Activation energies of L* and ΔE* values were determined as 34.04 and 79.16 kJ/mol, respectively. Results suggest that L* and ΔE* values may be used as color control indicators during roasting of corn kernels.     

Image Processing Applied to Classification of Avocado Variety Hass (Persea americana Mill.) During the Ripening Process

This work was undertaken to analyze the ripening process of avocados variety Hass (Persea americana Mill.) by image processing (IP) methodology. A set of avocados (10 samples) was used to follow the changes in image features during ripening by applying a computer vision system, extracting color and textural parameters. Other 16 avocados were used to evaluate the firmness and mass loss. Three maturity stages of avocados were established, and a classification was obtained by applying principal component analysis and k-nearest neighbor algorithm. During the ripening process (12 days), avocado firmness decreased from 75.43 to 2.63 N, while skin color values kept invariable during 6 days; after that, a decrement in the peel green color (a*) was observed (−9.68 to 2.32). Image features showed that during ripening the color parameters (L*, a*, and b*), entropy (4.29 to 4.00), angular second moment (0.287 to 0.360), and fractal dimension (2.58 to 2.44) had a similar path as compared to mass loss, a*, and firmness ripening parameters, respectively. Relationships between image features and ripening parameters were obtained. The parameter a* was the most useful digital feature to establish an acceptable percentage of avocado classification (>80%) in three different maturity stages found. Results obtained by means of IP could be useful to evaluate, at laboratory level, the ripening process of the avocados.     

Meat Color and Biochemical Characteristics of Unacceptable Dark-colored Broiler Chicken Carcasses

Spectrocolorimetry, pH, TBARS, total pigment and myoglobin were measured in normal and abnormally dark-colored broiler chicken breast muscle. Analyses of L*, a* and b* values revealed that a* values were highly sensitive and specific to differentiate normal from dark-colored carcasses and thus could be used as a potential diagnostic method for carcass classification at slaughter. Color characteristics (L*, a*, and b* values), pH, total pigment, myoglobin, and iron concentrations were all significantly different in dark-colored muscle when compared with normal muscle. TBARS values and percentage moisture for the two groups were not different.     

Evaluation of Venison Color by an Objective Method using CIELAB Values

A trained color panel was used to score both venison color and color acceptability for comparison with instrumental color measurements. Panel color scores were highly correlated with acceptability (r = 0.97) and could be predicted from CIE L*, a* and b* values by regression (R² (adj) = 0.84). The use of a* alone explained the greatest amount of variation R² (adj) = 0.78), and the inclusion of both L* and b* significantly improved the model. The use of hue angle and chroma either individually or in combination with L* did not provide better relationships. The use of L*, a* and b* is recommended for satisfactory prediction of panel color scores of venison with no less than three observations per sample.     

DIFFERENCES IN THE RATE OF COLORATION IN TOMATO FRUIT

The evolution of fruit color of twelve tomato (Lycopersicon esculentum Mill.) cultivars during ripening was evaluated. Final color of each of the cultivars was determined by calculating its fresh tomato color index (TCI_f). Luminosity (L*), red-green component (a*), a*/b* ratio, hue angle (h*), dominant wavelength (DW) and fresh tomato color index (TCI_f) were the parameters that best differentiated the ripening stages of tomato fruit. Dominant wavelength and purity of excitation were correlated with a* and b*. Fresh tomato color index (TCI_f) was related to the luminosity (L*) and yellow-blue component (b*).     

基于计算机视觉的鲶鱼肉色泽测定系统

采用色差计与计算机视觉系统(computer vision system,CVS)两种方法分别测定鲶鱼(Clarias leather)冰藏18 d期间鱼肉的色泽变化,探讨CVS方法测定鱼肉色泽(L*、a*、b*)的可行性。结果表明,两种方法所得的冰藏期间鲶鱼肉色泽变化趋势相同,且所得的总色差(ΔE值)基本相等。鱼肉冰藏期间明度(L*值)和ΔE值随着冰藏时间延长而逐渐升高(P0.05);红度(a*值)在前3 d缓慢升高,之后显著下降(P0.05);黄度(b*值)无显著性变化(P0.05)。通过色差计测量值对CVS测量值进行校正并验证可知,其校正值与色差计测量值无显著性差异(P0.05),且二者L*、a*、b*值的线性相关系数为0.89~0.97,表明CVS测量值经校正后,能准确地检测出冰藏期间鲶鱼肉的色泽变化,从而实现鱼肉色泽的快速测定。     

Computer Vision System Applied to Classification of “Manila” Mangoes During Ripening Process

Mango is an important crop that is marketed on a large scale around the world. The degree of ripeness of mangoes is an important quality attribute that has traditionally been evaluated manually through their physicochemical properties and color parameters, but recent non-destructive technologies such as computer vision systems (CVS) are emerging to replace these destructive, slow, and costly methods by others that are faster and more reliable. In the present work, physicochemical properties and color parameters obtained using a CVS at laboratory level were linked to establish the ripening stages of mango cv. “Manila.” Classification process involving multivariate analysis was applied with the aim of using only color parameters to estimate levels of ripeness. A set of 117 mangoes was used to estimate the ripening index (RPI) from the physicochemical properties, and another set of 39 mangoes was used to validate the classification process in mangoes harvest in a different season. The RPI was useful for establishing three phases of maturation, namely: pre-climacteric, climacteric, and senescence. These showed correspondences with the color changes evaluated in two color spaces (CIELAB and HSB). Principal component analysis was efficient in selecting the most significant variables and separating the mangoes into the three ripening stages. Multivariate discriminant analysis made it possible to obtain classification rates of 90 % by using only a*, b*, H and S color coordinates, the CIELAB system being, in general, more efficient at classification than HSB. The results obtained showed that CVS developed for the study can be used as a useful non-invasive, efficient method for the evaluation of the ripeness of mangoes.     

COLOR CHANGES IN BANANAS AND PLANTAINS DURING STORAGE

Two cultivars, namely Cavendish bananas (Musa AAA Group) and plantains (Musa AAB Group) were used to study the changes in their peel color during storage at various temperatures. Gas-treated and nontreated fruits, and the L* a* b* system were used. The temperature effect on the color parameters was mainly through the interaction with the gas treatment, variety and storage time; however, redness (a*) for gas-treated bananas was expressed as a *=−20.1 + 0.14TD, (T= temperature, D = day). Similarly, a*=−27.5 + 55 (TD)^1/2− 0.2 T D, predicted the degreening process in gassed plantains. The gas-treatment, storage time and variety all had a significant effect (p<0.01) on the L*a*b* parameters. Plantains lost the greenness during storage faster than bananas.     

纸片型1-MCP处理对安溪油柿果实采后生理和贮藏品质的影响

研究了纸片型1-甲基环丙烯（1-methylcyclopropene,1-MCP）处理对安溪油柿果实采后生理和贮藏品质的影响。采后安溪油柿果实用1.35 μL/L的1-MCP处理12 h后,在（20±1）℃、相对湿度85%下贮藏。结果表明：与对照相比,1-MCP处理能有效降低采后安溪油柿果实呼吸强度;抑制果实表面色度a*值、b*值、C*值、L*值和色调角h的变化,抑制果皮叶绿素含量下降和类胡萝卜素含量上升,降低果实转红指数,并保持较好的果实外观色泽;此外,1-MCP处理能保持较高的果实硬度及可溶性固形物、可滴定酸、总糖、蔗糖、还原糖质量分数和VC、单宁含量,减少果实质量损失。因此认为,1.35 μL/L纸片型1-MCP处理可有效延缓采后安溪油柿果实后熟衰老、改善果实贮藏品质。