Subjective Assessments

How the rheological properties measured by instruments, as just described, relate to the grader's or the consumer's assessments of the cheese remains to be considered. The emphasis in this article has been on the measurement of the firmness of cheese which arises from its structure. It should be stressed that meaningful comparisons can only be made between instrumental and subjective methods if the subjective terminology is unambiguous and the instrumental measurements precise. Early experiments on single varieties of cheese showed that the subjective assessment of firmness, which is a fairly simple concept, correlates very highly with measurements made with simple apparatus, such as the Ball Compressor (81). But a simple correlation by itself does not indicate to what extent the instrumental measurement should be used to predict a typical user's appraisal. Nor can the results of experiments on a single variety be extrapolated to other types of cheese without verification. Some authors have arbitrarily assigned a specific consumer quality to a particular instrumental reading. For instance, the quasi-modulus calculated from a simple compression test (27), the yield value given by a cone penetrometer (22), and the stress at 80% compression have all been proposed as measures of firmness. The recovery after a limited compression (29,82), arbitrarily decided upon, has been used as an indication of springiness. These intuitive opinions may help visualize the significance of an instrumental measurement and are probably adequate for internal comparisons within a single investigation, but they lack scientific rigor.

The force-compression test, giving as it does a characteristic curve with several readily identifiable features, provides a number of potentially useful parameters. In Figure 26 the values of hardness as assessed by a panel, of a number of different cheeses, versus the stress measured at 80% compression are plotted (73). A logarithmic regression line has been drawn through the points. The standard deviation about this regression line was no greater than that due to the differences among the panel. In this case, then, using the regression line, the instrumental reading can be safely used to predict that panel's assessments. In the same series of experiments the instrumental measurements were carried further. As soon as the compression had reached 80% the compressing plates were withdrawn and the recovered height of the sample was measured. At the same time the springiness was assessed subjectively. As has already been pointed out, springiness involves not only the extent of recovery but also its speed; possibly all individuals will have, subconsciously, their own ideas of the relative contribution of the two to the final judgment. As was to be expected, there was poorer agreement among the panel members in this part of the experiment. Even so, there was a highly significant correlation between the measured recovery and the average panel assessment of springiness.

The relation between user acceptance and instrumental rheological measurement is an ongoing study (82). The few examples cited above show that, if the proper parameter is chosen and the terms clearly understood, Theological measurements can successfully predict users' assessments.

Homemade Pet Food Secrets

Homemade Pet Food Secrets

It is a well known fact that homemade food is always a healthier option for pets when compared to the market packed food. The increasing hazards to the health of the pets have made pet owners stick to containment of commercial pet food. The basic fundamentals of health for human beings are applicable for pets also.

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