A VERSATILE FOOD RHEOMETER

A new texture test instrument is described that applies linear or rotary deformations, singly or in combination, to food samples. A range of texture test cells and mixing, consistometer or viscometer attachments are adaptable to this apparatus so that many test methods presently used to measure the properties of foods can be performed with the instrument. Different transducers can be installed to detect force, torque, deformation and deformation rate, which are precisely recorded electronically. Environmental and sample temperature controls are built into the equipment. Application of the apparatus is illustrated with measurements of consistency during the formation of wiener emulsions and the rupture property of the wieners.     

FOOD TEXTURE MEASUREMENTS IN CANADA

A survey of the food industry, government agencies and educational institutions dealing with foods has been conducted to establish the nature and extent to which instrumental texture measurements are employed in Canada. Two hundred and fifteen questionnaires were sent out and 123 (57%) returned. Of those replying, 52% were using texture evaluation instruments. Within the food industry the use of texture measuring instruments was as follows: meat 36%; fish 20%; canner/freezer 79%; dairy 42%; confectionery 73%; baking 50%; fats and oils 78%; multi product 77%; beverage 0%. Most widely used instruments in the quality control area were rotational viscometers and penetrometers. The more complex instruments, such as the Universal Testing Machine and the Shear Press, were used to a larger extent in the research area. The use of some instruments appeared to be restricted to particular commodity groups. The questionnaire dealt among other things with the use of taste panels, statistical evaluation of results, and the need for expanded use of instruments. There was general agreement that more standardization of methods is desirable.     

Use of gelatin gels as a reference material for performance evaluation of meat shear force measurements

Abstract: Establishing standards for meat tenderness based on Warner–Bratzler shear force (WBSF) is complicated by the lack of methods for certifying WBSF testing among texture systems or laboratories. The objective of this study was to determine the suitability of using gelatin gels as reference materials for performance testing of texture measurement systems. Three replications of 5 gels (15%, 20%, 25%, 30%, and 35% gelatin) were prepared, vacuum packaged, and stored at 4 °C until use. Three randomly selected strips from each gel were subjected to WBSF testing on 4 instruments (A, B, C, or D) on days 1 and 8. Additional strips from each gel were subjected to WBSF testing on instruments A and C on day 29. Regression line estimates for each set of gels were analyzed. Gel WBSF values ranged from 10 to 177 N. The WBSF by gel concentration response was highly linear (P < 0.0001) for all replications, instruments, and days of analysis. R²‐values across all sets of gels ranged from 0.9562 to 0.9998. On days 1 and 8, instruments A and D exhibited higher slope (P < 0.0001) and lower intercept (P < 0.0001) estimates than instruments B and C. Regression line parameters (slope, intercept, and R²‐values) were not influenced (P > 0.05) by length of gel storage (1, 8, and 29 d). Data from this study suggest that gelatin gels can be used for evaluating WBSF values from various instruments and for validating the performance of meat shear force testing. Practical Application: Validating the performance of meat shear force testing is vital to establishing meat tenderness standards. The gelatin gel standards developed in this study exhibited a highly linear, repeatable relationship with shear force and were found to be stable for at least a month. These gel standards would provide a tool for the meat industry to harmonize shear force measurements across laboratories and various texture measuring instruments.     

MEASUREMENT OF EGGSHELL STRENGTH*

Techniques used to measure the eggshell strength and associated parameters are reviewed. Much of the early research was based on crude instruments that did not adequately control test conditions, particularly the rate of applying force to the shell. Better instruments have been used recently to obtain precise readings. A significant advance has been the development of techniques to describe the physical properties of the shell material. This is potentially more meaningful than the empirical comparisons of egg behaviour, and is leading to a better understanding of the shell fracture mechanism. Two practical tests are currently available to the biologist for non-destructive measurements: specific gravity of the egg and shell deformation under a non-destructive force. Both predict - with acceptable precision - the shell fracture force. Eggshell strength has been investigated for over 70 years, but an ideal test method has yet to be found, and research is still required.     

Understanding and predicting sensory crispness of deep‐fried battered and breaded coatings

Crusted crispness refers to coatings with a dry and brittle surface contrasting a high‐moisture core; it is desirable for the enjoyment and quality of deep‐fried goods. This study aims to investigate instrumental measurements and sensory measurements of crispness. Deep‐fried breadcrumb coatings of eight sizes were investigated: 4.0 mm, 2.8 mm, 2.0 mm, 1.4 mm, 1.0 mm, 710 μm, 500 μm, and 355 μm. Sensory profiling was carried out to develop a tailored lexicon for deep‐fried battered and breaded shrimp. Principal component analysis highlights that large breadcrumb sizes correlate with crispness, hardness, particle size, surface color, color uniformity, surface irregularity, total porosity, maximum force, area, drop in force, number of sound peaks, and sound pressure level. Agglomerative hierarchical clustering was used to confirm clustering of samples according to breadcrumb size. Multiple factor analysis confirmed overall correlation between sensory measurements and instrumental measurements (RV = 0.810). Partial least squares regression was used to develop a predictive model for crispness from instrumental measurements (R² = .854). The use of texture analysis and Acoustics provide information of the structures strength and deformation behavior, while X‐ray microCT provides a high resolution and noninvasive method that acquires information on the internal morphology. These instrumental methods collectively demonstrate the relationship between microstructure to sensory. This study investigates how a change in the microstructure of deep‐fried battered and breaded coatings affect crispness perception. These changes were investigated analytically and by using a sensory panel, this is important from a manufacturing perspective in order to understand what the major contributors are to a crisp texture. The key highlights of this study include both instrumental measurements and sensory measurements can be used to measure crispness as both types of testing are correlated. Changes in the size of breadcrumbs affect both instrumental measurements and sensory measurements. A predictive model can be re‐simulated to allow prediction of crispness in deep‐fried battered and breaded coatings.     

Mechanical behaviour of hazelnuts used for table consumption under compression loading

Nuts of four hazelnut varieties and five new selections used for table consumption were compressed at the moisture content of 6% wet basis to measure shell resistance to breakage. Rupture force, rupture energy and nut specific deformation were measured under three compression loading positions. Physical parameters of nuts were also evaluated to relate them to the data obtained by compression test measurements. Rupture force and nut specific deformation are the most discriminant parameters that can be used to describe the behaviour under compression, while rupture energy values show fewer differences among the considered varieties. The values of force required to break nut shell ranged from 322.2 to 769.3 N. The lowest values of force were generally obtained along the y‐axis, the transverse axis containing the major dimension at right angles to the longitudinal axis. Nut specific deformation ranged from 3.35 to 11.76%. Correlations between physical and texture parameters showed that values of force, energy and deformation were dependent on different parameters that varied in the three considered axis. The most used varieties, Ennis and Barcelona, showed high mean values of force rupture to break shell and low deformability, while Tonda Giffoni and Tonda Bianca were easy to break. Among the new selections, L35 and B6, with mean values of force rupture less than 428 N and values of nut specific deformation higher than 8%, were suitable for table consumption. Copyright © 2006 Society of Chemical Industry     

SELECTING DEFORMATION RATES IN TEXTURE TESTS *

Abstract . Since mastication involves high deformation rates (150cm min^?1), the arbitrarily selected slow deformation rates usually used in instrumental texture tests can lead to erroneous results and lack of correlation with sensory evaluation with respect to the order of sample ranking. Sophisticated instrumentation that is costly to operate is required to accurately simulate the deformation rates operating in the mouth. It is suggested that instrumental data obtained at slow rates could be evaluated in a more meaningful manner if series of similar samples were tested at increasing deformation rates and the plotted force/deformation curves extrapolated to 150cm min^?1. It is implied that recording systems would be more useful, if in addition to force, they sensed the rate of force change with deformation rate.     

Pin Versus Disk Punch Measurements of Frankfurter Texture

Puncture measurements were made of frankfurter texture using either a pin (straight-sided shaft) or a disk (narrow shaft) punch. The forces resisting pin punch puncture were compression, tension, and friction, whereas no frictional forces were involved when the disk punch was used. Within a given set of samples, both pin and disk measurements gave the same value (avg. = 413.6 ± 1.9) for the maximum force at the yield points when extrapolated to zero penetration distance. For heterogeneous samples from a previous study, the values ranged from 34.7 to 574.9g. Negative force increments in puncture measurements are explained on the basis of deformation of the gel.     

SENSORY AND MECHANICAL ATTRIBUTES OF GEL TEXTURE

Eighteen experienced judges evaluated the texture of gels varying in gelatin concentration (22-45 g/L) in terms of firmness by oral and manual shear and compression, cohesiveness, and extent of breakdown in the mouth. Manual compression and biting with the front teeth discriminated well across gel concentrations. All sensory measures except extent of breakdown increased with gelatin concentration. Instron (IUTM) measurements showed that increasing gelatin concentration resulted in an increase in maximum force and force/deformation, but had little effect on deformation at yield and rupture or in elasticity and cohesiveness. Results from mechanical measurements varied with the type of force applied (compression, shear or puncture), the loading rate (50 or 200 mm/min), and the extent of deformation attained (40–90%). The highest discrimination across gel concentrations was achieved with shear force at a rate of 200 mm/min and at greater deformations. Sensory responses correlated most highly with the following IUTM measurements: (1) Compression forces at yield and at deformations of 70 and 85% at the higher crosshead speed; (2) Compression forces below the yield point at the lower crosshead speed; and (3) Shear forces measured at maximum deformation (90%) at 200 mm/min.     

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.     

质构仪在大米品质评价中的应用研究

以13种稻谷样品为材料,用质构仪测定米饭的硬度、黏度、黏着性、弹性、回复能量、回复形变、最终负载、硬度能量、僵化度9种质构指标;用蒸煮法测定大米吸水率、膨胀体积、米汤碘蓝值、米汤干物质等蒸煮指标,分析研究大米质构品质指标与蒸煮品质指标的相互关系。研究结果表明:米饭的弹性与膨胀率、碘蓝值呈显著的正相关,粳米相关系数为0.853、0.774,籼米为0.827、0.816;黏度与吸水率呈显著的正相关,相关系数为粳米0.971、籼米0.824;黏着性与米汤干物质也有显著的相关性,粳米相关系数为0.788,籼米为0.829;回复能量、回复形变等指标与蒸煮品质指标间没有显著的相关性;可用硬度、黏度、黏着性、弹性来评价大米的食用品质。     

ENGINEERING ASSESSMENT AND CRITIQUE OF INSTRUMENTS USED FOR MEAT TENDERNESS EVALUATION*

A review of the methods used to measure meat texture indicates considerable confusion in terminology, test conditions, and interpretation of the readings that makes evaluation of the results a complex task. Standardization of the methods appears premature and until this is accomplished, the applied methodology must be reported fully. Errors due to instrument design can no longer be accepted since modern instruments that overcome this are readily available. A common error in terminology or interpretation is the use of the term shear to describe the rupture imposed on meat samples in popular tests. It is shown that meat generally ruptures in tension which is also the case during mastication; this explains why empirical measurements often relate to sensory readings. It is concluded that there is room for improvement in existing methods, particularly in the interpretation of the results using common sense, close observation and theoretical analysis.     

CONTROL OF DEFORMATION IN TEXTURE TESTS *

Abstract. The motion of the Instron crosshead during small deformations (e. g. 0.25 mm) in tensile tests performed at the available range of deformation rates was examined. Large errors are introduced in the deformation readings if it is assumed that the deformation rate was constant at the rate selected because, as with any instrument of this type, the crosshead requires time to accelerate to the selected speed. The characteristic behaviour of the food is subject to misinterpretation if the applied deformation profile is unknown. It was found that the errors are larger when the instrument is used incorrectly by performing tensile tests below the crosshead. The work demonstrated some of the limitations that must be recognized when applying the Instron, or any deformation mechanism, to certain texture tests. It is concluded that food behaviour, under small deformations, could be recorded precisely and interpreted correctly providing that both the force and deformation are recorded against time. Control of the crosshead stopping and reversal points was also examined, particularly in relation to the instrumental texture profile analysis. Crosshead acceleration affects the readings and interpretation of the data at the reversal point. If the deformation rate is changed, the stopping point must be adjusted.     

Understanding the texture of low moisture cereal products: mechanical and sensory measurements of crispness

The texture of extruded starch products has been measured sensorially and instrumentally. The instrumental data were analyzed using different approaches such as fractal analysis and peak analysis. The data showed useful correlations between sensory crispness and crackliness and a parameter obtained from the application of a newly developed fractal method to analyze the force deformation curve obtained from a penetration test of the cereal samples. This suggests that fractal analysis of the force‐deformation plots could be used instead of sensory analysis. Moreover, it was observed that an increase in water content altered the texture of starch based samples from crispy to crackly, whereas the texture of starch‐sucrose samples remained unchanged in the same hydration range. © 2000 Society of Chemical Industry     

Evaluation of 1047-nm photoacoustic instruments and photoelectric aerosol sensors in source-sampling of black carbon aerosol and particle-bound PAHs from gasoline and diesel powered vehicles

A series of measurements have been performed at Hill Air Force Base to evaluate real-time instruments for measurements of black carbon aerosol and particle-bound PAHs emitted from spark and ignition compression vehicles. Vehicles were operated at idle or fast idle in one set of measurements and were placed under load on a dynamometer during the second series. Photoacoustic instruments were developed that operated at a wavelength of 1047 nm where gaseous interference is negligible, although sensitivity to black carbon is good. Compact, efficient, solid-state lasers with direct electronic modulation capabilities are used in these instruments. Black carbon measurements are compared with samples collected on quartz fiber filters that were evaluated using the thermal optical reflectance method. A measure of total particle-bound PAH was provided by photoelectric aerosol sensors (PAS) and is evaluated against a sum of PAH mass concentrations obtained with a filter-denuder combination. The PAS had to be operated with a dilution system held at approximately 150 degrees C for most of the source sampling to prevent spurious behavior, thus perhaps compromising detection of lighter PAHs. PA and PAS measurements were found to have a high degree of correlation, perhaps suggesting that the PAS can respond to the polycyclic nature of the black carbon aerosol. The PAS to PA ratio for ambient air in Fresno, CA is 3.7 times as large in winter than in summer months, suggesting that the PAS clearly does respond to compounds other than BC when the instrument is used without the heated inlet.     

Quality of peas modelled by a structural equation system

The quality of peas has been studied in a joint project between a pea producing company in Denmark and several research institutions. The study included quality from a consumer point of view based on market research and quality from more internal company points of view based on measurement of physical/chemical attributes that are expected to describe quality. The purpose of the work was to use the considerable amounts of information in a decision oriented way to obtain answers to questions like: (1) How do consumers perceive quality? (2) Is it possible to describe the variation in preferences expressed by consumers as a function of the objective measurements of quality e.g. the physical/chemical variables? (3) Which of the measured objective variables are most important for further product development? In the paper we describe consumer evaluations as a function of physical/chemical variables in a PLS structural model with the Total Food Quality Model as starting point. The results show that texture and flavour do have approximately the same effect on the consumers' perception of overall quality. Quality development goals for plant breeders would be to optimise perrceived flavour directly by increasing the amount of sugars and more indirectly by improving the perception of colour through darker and less yellow peas. Perceived texture can be optimised by focusing on selected texture measurements.     

猪肉质构的仪器测定与感官评定之间的相关性分析

以熟肉为研究对象,比较感官评定和两种仪器测定方法(剪切法和质构剖面分析)之间的差异和关联性。结果表明:剪切力与感官评定的硬度、多汁性呈显著相关性(r=0．73、-0．71);质构剖面分析硬度与感官评定的硬度相关性显著(r=0．81),质构剖面分析的粘聚性与感官评定的弹性、多汁性、油性分别呈显著相关性(r=-0．79、-0．67、-0．81)。通过建立仪器分析与感官评定间的数学模型,本实验提示质构剖面分析更能全面预测猪肉感官品质。进一步的实验参数验证了质构剖面分析回归方程预测的准确性。     

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.     

基于电子鼻检测技术分析不同马铃薯粉添加量对面包品质的影响

通过测定面包的比容、水分含量、水分活度、色泽和质构,研究不同马铃薯粉添加量(0、5%、10%、15%、20%和25%)对面包品质的影响,并结合电子鼻分析,进行马铃薯面包品质的快速检测。结果表明,在不同马铃薯粉添加量条件下,面包的比容、水分含量、水分活度、色泽和质构存在显著差异(p<0.05)。随着马铃薯粉添加量的增加,面包的硬度和咀嚼性呈现先减小后增大的趋势,而弹性先增大后减小;比容呈现先减小后增加再减小的趋势,而粘附性先降低后增加再降低,水分含量、红色度a*逐渐升高,水分活度、亮度L*值、内聚性逐渐降低。马铃薯粉添加量在15%时,面包的综合品质得到改善。同时,电子鼻检测数据结果与面包的比容、水分含量、水分活度、色泽和质构之间具有较好的相关性,相关系数均在0.8以上。因此,采用电子鼻对面包品质评价具有一定的可行性,可以很大程度上代替多种检测仪器设备对面包品质进行综合评价,是一种方便快捷的检测方法。