PREDICTION OF INSTRUMENTAL AND SENSORY TEXTURAL CHARACTERISTICS OF MAHON CHEESE FROM ULTRASONIC MEASUREMENTS

Ultrasonic velocity was related to sensory and instrumental texture measurements. A semi-logarithmic model (Weber-Fechner) was used to relate the sensory and instrumental texture measurements. The ultrasonic velocity ranged from 1650 to 1723 m/s for the softest and hardest cheese, respectively. As expected from theoretical equations, the ultrasonic velocity was related to the square root of the instrumental measurements. The deformability modulus (r²=0.93) and the slope in puncture (r²=0.85) were the most closely related parameters. A model developed from the relationship between sensory and instrumental texture and the relationship between ultrasonic velocity and instrumental texture, was used to relate velocity to sensory measurements. Elasticity (r²= 0.84) and firmness (r²= 0.81) were the sensory attributes which best correlated with ultrasonic velocity. From the obtained results, it was concluded that ultrasonic velocity measurements could be used to assess instrumental and sensory properties of Mahon cheese texture nondestructively, and therefore could be used for grading purposes.     

INSTRUMENTAL AND SENSORY TEXTURE ASSESSMENT AND FRACTURE MECHANISMS OF CHEDDAR AND CHESHIRE CHEESES

Textural attributes of Cheddar and Cheshire cheeses, falling within narrow compositional ranges, were assessed by sensory panels, and from force-compression curves generated by compression between two plates, and, for Cheddar cheese only, by penetrometry. Individual sensory measurements did not relate well to any instrumental one, and were better at discriminating between cheeses. Samples of each cheese variety were fractured in different ways and the fracture surfaces were examined in a scanning electron microscope. Fracture surfaces were formed by cutting directly through the matrix, tearing of the matrix along planes high in fat or cracking at grain boundaries. It is suggested that consideration of fracture mechanism may aid the selection and development of useful instrumental methods for texture assessment of cheese.     

Relationship between Sensory and Instrumental Hardness of Commercial Cheeses

ABSTRACT: The effect of deformation (10% to 90%) and deformation rate (0.2 to 10 mm/s) on both maximum compression force and correlation between sensory and instrumental measurements of hardness were investigated for 26 commercial cheeses. Log-linear regression models were used to model the relationship between deformation rate and maximum compression force and fitted well to the relationship, indicating that maximum compression force is a log linear function of deformation rate. Deformation had a large effect on the correlation between sensory and instrumental hardness, while deformation rate had a small effect. The optimal deformation and deformation rate for the maximum correlation were 70% to 90% and 1.0 mm/s, respectively. This implies that an optimal combination of deformation and deformation rate can be used for maximizing the correlation between sensory and instrumental hardness for cheese products.     

TEXTURE ANALYSIS OF CHEDDAR CHEESE MADE FROM ULTRAFILTERED MILK

The textural properties of Cheddar cheese made from ultrafiltered milk were assessed. Cheddar cheeses were prepared from 1.5- and 2.0-fold concentrated milk and ripened for three months. Textural characteristics of the UF cheeses were compared to control and commercial Cheddar cheeses by sensory and instrumental measures. The texture of cheese made from UF milk differed from the control commercial Cheddar cheeses. According to the trained sensory panel, the UF cheeses were harder and more rubbery, crumbly, chewy and grainy than the control and commercial Cheddar cheeses (P <0.01). The texture profile analysis (TPA), conducted using the Instron, did not correspond to the sensory measurements nor was it successful in discriminating among the cheese samples. Lack of agreement between the sensory and instrumental tests was attributed to differences in the testing conditions and procedures of the two methods. Instrumental tests should be validated against sensory measures in order to be useful as measures of palatability. Consumer preferences for the commercial, control and UF Cheddar cheeses were significantly different (P < 0.01), the UF cheeses being less preferred in terms of flavor, texture and overall acceptability.     

Modelling of sensory and instrumental texture parameters in processed cheese by near infrared reflectance spectroscopy

This study investigated the application of near infrared (NIR) reflectance spectroscopy to the measurement of texture (sensory and instrumental) in experimental processed cheese samples. Spectra (750 to 2498 nm) of cheeses were recorded after 2 and 4 weeks storage at 4 degrees C. Trained assessors evaluated 9 sensory properties, a texture profile analyser (TPA) was used to record 5 instrumental parameters and cheese 'meltability' was measured by computer vision. Predictive models for sensory and instrumental texture parameters were developed using partial least squares regression on raw or pre-treated spectral data. Sensory attributes and instrumental texture measurements were modelled with sufficient accuracy to recommend the use of NIR reflectance spectroscopy for routine quality assessment of processed cheese.     

Use of principal component analysis to evaluate the physical properties of Mahon cheese

 The texture, colour and water activity of the seven existing types of Mahon cheese, manufactured under the Mahon cheese Appellation of Origin, were studied using eight physical variables. Four of the types are industrially manufactured [fresh (less than 10 days of ripening), half-ripened (2–5 months of ripening), ripened (5–10 months of ripening) and old-ripened (more than 10 months of ripening)] and three are traditionally manufactured (half-ripened, ripened and old-ripened). ANOVA, Tukey's multiple range test and principal component analysis (PCA) were used. Mahon cheeses from different ripening periods exhibited significant differences in water activity and yellowness values (P<0.001). PCA reduced the eight physical variables to two independent components, which accounted for 84.4% of the total variance. The first principal component (PC1) separated cheeses characterised by high water activity, high springiness values and slight yellowness from those with high hardness and puncture force; PC1 therefore distinguished among samples from different ripening periods. Cohesiveness, chewiness and gumminess were highly correlated in the second principal component, which could be interpreted as an index of cohesiveness. Received: 8 February 1999     

Cheese maturity assessment using ultrasonics

The relationship between Mahon cheese maturity and ultrasonic velocity was examined. Moisture and textural properties were used as maturity indicators. The ultrasonic velocity of the cheese varied between 1630 and 1740 m/s, increasing with the curing time mainly because of loss of water, which also produced an increase of the textural properties. Because of the nature of low-intensity ultrasonics, velocity was better related to those textural parameters that involved small displacements. Ultrasonic velocity decreased with increasing temperature because of the negative temperature coefficient of the ultrasonic velocity of fat and the melting of fat. These results highlight the potential use of ultrasonic velocity measurements to rapidly and nondestructively assess cheese maturity.     

Application of principal component analysis to chemical characteristics of Mahon cheese

 The chemical composition of the seven existing types of Mahon cheese, manufactured under the “Mahon” cheese Appellation of Origin, were studied. Of the cheeses, four were industrial (fresh, half-ripened, ripened and old-ripened) and three were traditionally manufactured (half-ripened, ripened and old-ripened). The chemical parameters were evaluated using ANOVA, Tukey’s multiple range test and principal component (PCA) analyses. Significant differences were found between Mahon cheeses ripened for different times in terms of moisture and non-protein nitrogen (NPN) contents (p <0.001); these differences were found to be independent of the manufacturing methodology, i.e. industrial or traditional. The ash and fat contents of industrially manufactured cheeses were significantly different from those in traditionally manufactured cheeses (p <0.001). PCA reduced chemical variables to two independent components: the first principal component was high in moisture, NPN content and water activity; the second, in NaCl, ash and fat contents. These results indicate that the seven types of Mahon cheese described by the “Mahon” cheese Appellation of Origin can be differentiated by their chemical characteristics. Received: 4 April 1997 / Revised version: 4 July 1997     

Differentiation and grouping of chemical characteristics of Mahon cheese

 Cluster analysis of cases (CAC) and variables (CAV) and stepwise discriminant analysis (SDA) were applied to estimate the usefulness of various chemical determinations for the characterization and differentiation of the seven types of Mahon cheese, four industrially manufactured (fresh, half-ripened, ripened and old-ripened cheeses) and three traditionally manufactured (half-ripened, ripened and old-ripened cheeses). CAV showed that, on the one hand, moisture, non-proteic nitrogen (NPN) and water activity measurements, and on the other ash, NaCl and fat measurements are very similar variables. Using SDA, it was possible to differentiate between industrially and traditionally manufactured cheeses by measuring NaCl and fat contents, and also between the four stages of ripening suggested by the "Mahon" cheese Appellation of Origin according to the moisture and NPN variables. Using classification functions obtained by SDA, 94.1% of cheese samples were correctly classified into traditional or industrial groups, and 89.7% of samples into fresh, half-ripened, ripened and old-ripened groups (jackknife validation). Received: 15 July 1997 / Revised version: 2 February 1998     

Comparison of instrumental and sensory evaluation of texture of cured and cooked beef meat

The instrumental and sensory texture attributes of beef muscles (M. longissimus dorsi and M. semimembranosus) were compared after curing and thermal treatments. Shear, compression and puncture tests were carried out with an UTM Instron 4301 and the sensory evaluation was made with the score method. The force values obtained for puncture test gave a greater degree of correlation with the sensory tenderness, hardness and elasticity than the shear test forces. The shear test forces were found to significantly correlate with sensory tenderness only for muscles with perpendicular orientation of fibres to the direction of shear blade movement. The evaluation of beef texture with compression test was dependent on the level of sample deformation degree. The force values of compression were found to correlate significantly with elasticity and juiciness of meat up to 60% deformation levels, but at deformation levels higher than 60% appeared significant correlation with tenderness and hardness. The obtained results showed the usefulness of puncture test with proposed parameters for the instrumental measurements of beef texture.     

PREDICTION OF SENSORY TEXTURE OF FETA CHEESE MADE FROM ULTRAFILTERED MILK BY UNIAXIAL COMPRESSION AND SHEAR TESTING

The ability to predict sensory texture properties of Feta cheese made from ultrafiltered milk (UF-Feta) from uniaxial compression, small shear deformation measurements (frequency sweep, strain sweep, relaxation) and indices of proteolysis was studied. In principal component analysis (PCA) some of the instrumental variables were highly correlated, e.g. the moduli from uniaxial compression and shear measurements; and strain at fracture from uniaxial compression and indices of proteolysis. PCA of the six sensory attributes determined by a trained panel showed that mainly one type of information was present in the sensory results. Partial Least Squares regression (PLS) of all results revealed that stress at fracture from uniaxial compression was the individual instrumental parameter having the highest correlation with the sensory texture attributes. Of these, the three firmness attributes were best predicted by the instrumental parameters. As the shear measurements were not very useful for prediction of sensory texture properties by themselves, and as the increase in prediction precision by inclusion of these measurements was marginal, it is suggested that either stress at fracture alone, or together with three other parameters from uniaxial compression should be used to describe texture properties of UF-Feta cheese.     

Invited review: Sensory and mechanical properties of cheese texture

Instrumental mechanical properties (instrumental tests that measure force and deformation over time) of cheese and cheese texture (sensory perception of cheese structure) are critical attributes. Accurate measurement of these properties requires both instrumental and sensory testing. Fundamental rheological and fracture tests provide accurate measurement of mechanical properties that can be described based on chemical and structural models. Sensory testing likewise covers a range of possible tests with selection of the specific test dependent of the specific goal desired. Establishing relationships between instrumental and sensory tests requires careful selection of tests and consideration and analysis of the results. A review of these tests and a critical analysis of establishing relationships between instrumental and sensory tests is presented.     

Comparison of electromyographic pattern of sensory experts and untrained subjects during chewing of Mahon cheese

Use of electromyography (EMG) to monitor mastication is a relatively new concept in assessing food physical and sensory properties. Although expert assessment of cheese characteristics is widely used, the effect of training in sensory analysis on mastication patterns, as assessed using EMG is not well known. Nine samples of the same Mahon cheese (60 days ripening) were given to 24 subjects (8 experts, 16 untrained) and EMG recorded for each chewing sequence. Three samples were tested in a single session by each subject, and three sessions carried out on different days. EMG was recorded from four masticatory muscles for each subject. From EMG records the following was extracted: number of chews, chewing time, mean and maximum voltage of EMG bursts (i.e. chews) across chewing sequence, chewing work and chewing rate. No gender bias was found for the EMG parameters considered, therefore, as regards gender, each group was considered to be homogeneous. Variability within-subjects across samples was greater for experts than untrained subjects. Significant differences in chewing time, chewing work and chewing rate were found between the expert and untrained groups. Data analysis of the three sessions showed an influence of cognitive constructs, mediating states, on the chewing process. The experts were found to be goal driven as to their mastication process. Experts showed no significant differences between sessions, untrained subjects were found to vary their EMG output in successive sessions for number of chews, chewing time, mean voltage, and chewing work.     

五种苹果质构测定方法的比较及与感官评价的相关性分析

为比较5种苹果质构不同测定方法,采用剪切法、穿刺法和TPA压缩法测定了辽宁地区5种主栽苹果的质构特征,同时研究了不同测试条件对测定指标的影响,并分析了仪器测定与感官评价结果的相关性。结果表明剪切、穿刺和TPA压缩均能测得苹果的硬度特征,并区分不同品种间的差异,去皮果肉硬度大小依次为王林 > 红富士 > 国光 > 乔纳金 > 黄元帅;穿刺法检测显示果皮对苹果质构有显著影响(P<0.05),且不同穿刺部位的质构差异显著(P<0.05),其中果顶部位穿刺硬度值最大,其次为果肩和赤道;与感官评价相关性分析显示最大穿刺模量与感官脆性极显著相关(r=0.638,P<0.01),可作为苹果脆性的表征指标;对TPA法,随着压缩形变量增加,苹果硬度测定值显著增加(P<0.05),而内聚性显著减小(P<0.05),且形变量为25%时与感官评价相关性最好。本研究表明穿刺法和TPA法均适用于苹果质构的测定,果皮及穿刺位点对穿刺影响显著,最大穿刺模量可用于表征苹果脆性指标;压缩形变量为25%时TPA法所测得质构参数与感官评价结果相关性最好。     

A COMPARISON OF THREE INSTRUMENTAL TESTS FOR PREDICTING SENSORY TEXTURE PROFILES OF CHEESE

Multivariate analysis techniques were used to seek correlations between texture sensory attributes assessed by a trained professional panel and instrumental measurements (compression, puncture and penetration) carried out on various types of cheeses. Twenty-nine cheeses were assessed by the panel and instruments. Correlation was sought using Partial Least Squares regression. Hardness (R=0.87), springiness (R=0.98) and cohesiveness of mass (R=0.89) were best predicted by instrumental data from a cone penetration test. The prediction of cohesiveness was acceptable using any of the three instrumental tests performed (0.76相似文献   

FAT REPLACERS IN LOW-FAT MEXICAN MANCHEGO CHEESE

Low-fat Manchego cheeses (15 g fat/L milk) were prepared with three commercial fat replacers consisting of low methoxyl pectin (LMP), whey protein concentrate (WPC) and microparticulated whey protein (MWP). A low-fat cheese (15 g fat/L milk) without added fat replacer and a full-fat cheese (30 g fat/L milk) were prepared as controls. Cheeses were matured thirty days prior to instrumental texture profile analysis, microstructure analysis, and discriminative sensory evaluation. Scanning electron micrographs showed that the low-fat cheeses incorporating the LMP and WPC fat replacers lost the compact and dense protein matrix characteristic of the low-fat control cheese and exhibited hardness, springiness, cohesiveness and chewiness similar to the full-fat control cheese. No significant difference was found in the sensory characteristics between the full-fat control cheese and the cheese incorporating WPC.     

Free amino acids by high performance liquid chromatography and peptides by gel electrophoresis in Mahon cheese during ripening

The free amino acids and peptides contents of Mahon cheese during four months of ripening were studied using high performance liquid chromatography and gel electrophoresis, respectively. The total content of free amino acids generally increased throughout the ripening period, except in one batch. Phenylalanine, valine, proline, glutamic acid and isoleucine were the most abundant free amino acids in all the tests throughout the four month period. They accounted for between 67 and 80% of the free amino acids. No difference was found between the pattern of traditionally made and industrially made Mahon cheeses. Electrophoresis of soluble nitrogen showed the main whey proteins as well as other bands corresponding to peptides.     

Vane Rheometry for Textural Characterization of Cheddar Cheeses: Correlation with Other Instrumental and Sensory Measurements

The relationship between instrumental (vane method, texture profile analysis (TPA), uniaxial compression) and sensory texture measurements of Cheddar cheeses was investigated. A Haake VT 550 viscotester equipped with a four-bladed vane rotor was used for the vane test. Instrumental TPA was performed with a TA.XT2 Texture Analyser, and compression variables were calculated from TPA data. Vane parameters were significantly correlated with respective variables of compression and TPA (r=0.56-0.91), and sensory tests (r=0.54-0.88). Multivariate analysis indicated that seven sensory attributes of ten commercial Cheddar cheeses were satisfactorily predicted (calibration regression coefficient,R_cal >0.62) by variables of the vane, uniaxial compression and TPA tests. In particular, cheese firmness and cohesiveness evaluated by sensory panel were well described by vane stress and apparent strain. The results validate the vane method as an alternative to the existing cheese testing methods for rapid evaluation of cheese texture.