Sensory evaluation of fruits and vegetables

1. Sensory evaluation of fruits and vegetables

3. SENSORY AND OBJECTIVE QUALITY EVALUATION I. INTRODUCTION • Quality is an elusive property which can be defined as the sum total of those attributes which combine to make fruits and vegetables acceptable, desirable, and nutritionally valuable as human food. • The quality components are presented in Table 1. • It is essentially a composite concept which can be broken down into a number of distinct yet related aspects. • In the first place, appearance is obviously of significance and can be appreciated by visual examination.

5. Defects, due to several causes, which detract from the acceptability of a product, can be easily identified. • The size and shape of individual units is a factor in quality, while the development of other attributes indicates the stage of maturity. • An especially important visual feature is the color of the external surface.

6. II. SENSORY EVALUATION • Appearance, although most important, is by no means the sole criterion of quality. • Important also are the properties appreciated through other human senses: those of taste, smell and touch, which can be grouped together under the heading of color, flavor, and texture. • The attainment of a satisfactory color, flavor, and texture may often be associated with a certain development of color, but appearance can be a deceptive and completely satisfactory way of assessing flavor and texture.

11. Differences in growing conditions, in harvesting procedures, and in postharvest treatments combine with the variability of the produce itself to wide variations in quality, and many countries have minimum standards and systems of grading in an attempt to maintain some sort of consistency in the general quality of produce reaching the consumer. • The market for fruits and vegetables is an international one and the present trend is towards greater international standardization of grades of quality of fruits and vegetables.

12. FAO (Food and Agricultural Organization) and WHO (World Health Organization) have developed a Codex Alimentarius which has standards for a complete range of foods. • The Economic Commission for Europe (ECE) pioneered the formulation of international standards for fresh fruit and vegetable commodities and a number of existing European standards have already been adopted by the Organization for Economic Cooperation and Development (OECD), a body which includes the countries of western Europe, U.S., and Canada.

13. There is every reason to believe that in due course the standards laid down by the OECD will receive world-wide recognition and that a complete uniformity of standards will finally be achieved. • The OECD scheme lays down certain minimum requirements for material entering the international market and also institutes a number of quality classes

14. The minimum general requirements are as follows: I. The fruits or vegetables should be healthy and sound, that is to say, free from blemishes liable to affect their natural powers of resistance, such as traces of deterioration or decomposition, bruises, or unhealed cracks.

15. 2. They should be whole, clean, practically free from extraneous matter, free from any foreign taste or smell and without abnormal surface moisture. 3. They should be of normal size and appearance in regards to the variety, season and production area. 4. They should have reached a degree of maturity which will ensure the arrival of the produce in good condition.’

16. Three distinct classes are designated for quality: • (1) an “Extra” Class to include “produce of superior quality, of the shape, appearance, color and taste characteristic of the variety, virtually free from blemishes affecting their external appearance and particularly carefully packed”; • (2) Class I, “produce of good quality, ‘commercially’ free from blemishes and carefully packed”; and • (3) Class El, “produce which may have certain blemishes not impairing its intrinsic quality and which compiles with the minimum general requirements defined above”.

17. Specific standards are already laid down for a number of individual commodities. • In these, the necessary requirements for inclusion in each quality class are described in considerable detail, with explanatory illustrations, so as to enable these standards to be applied as uniformly as possible throughout the various member countries

18. The above methods and other systems of grading used in connection with trade between countries that are not members of the OECD are applied to specific fruits and vegetables crossing international boundaries, but government departments and trade associations in many countries also operate their own internal systems of quality grading.

19. Minimum standards are generally required by law, but grade specifications are often voluntary, for example, as those drawn up by the Agricultural Marketing Service of the United States Department of Agriculture, in cooperation with various groups interested in the marketing of fresh and processed fruits and vegetables. • In the United States, and to a lesser extent in other industrialized countries, a substantial part of the fruit and vegetable crop is taken by the processors and requirements are not necessarily the same as those which apply to the producer.

20. The quality of specifications for grading of fruits and vegetables is not easy, since several of the attributes which go to make up quality are essentially subjective properties. • Quality specifications inevitably lack precision and even when written up in considerable detail, they still suffer from the absence of satisfactory objective methods of measurement.

21. The United States assesses the quality of fresh fruits and vegetables by scoring a sample marked for different quality attributes by reference to a special scoresheet. • In this way, by adding the marks accorded for different features, a total score is obtained and this can be used as a measure for overall quality and a basis for quality grading. • The use of such a system raises the problem of deciding what proportion of the total available marks would be allocated to each of the various properties contributing towards the general quality over all the produce. • The U.S.A. uses a maximum score of 100

22. III. ORGANOLEPTIC QUALITY EVALUATION • Uniform samples are prepared (Figure 1) for quality evaluation. Organoleptic appraisals are made for color, flavor, texture, and aroma by a panel of ten trained judges or by a large consumer panel of nonsmokers. Numerical values (I0—Jike extremely—to I—dislike extremely) are assigned to fresh and processed fruits and vegetables (Table 2). The judges are instructed to appraise each sample and encircle the phrase which best describes their feelings about the sample. Following judging, preference scores for each sample are added together and divided by the number of judges to find the final average score. The samples are always

24. put in coded cups, placed on trays and placed in a judging room. The judging room is furnished with individual cubicles, each equipped with daylight intensity for color as nearly as possible (Figure 2). Each member of the panel judges the flavor, color, texture and aroma (Figure 3).

25. The flavor is tested for tasting sweetness, saltiness, sourness, and bitterness by the location and distribution of taste buds over the tongue and their specific locations (Figure 4). • Texture is judged by mouth feel or chewiness. Aroma is evaluated by smelling the samples. • Color is judged by its original and natural color and gloss40

26. IV. OBJECTIVE QUALITY • Color, flavor, and texture are complex properties. In order for the best possible use to be made of available methods for measurement in these cases, it is important that a proper • understanding be obtained of the particular attribute and of the mechanisms whereby it is appreciated by the individual consumer.

28. A. COLOR The appreciation of the appearance of any object depends on the formation of an image on the retina of the eye. • In order that an image be formed, a certain minimum amount of light must reach the eye from the object. • The glossiness of the surface of an object depends on the manner in which light is reflected from that surface, which in turn depends on the smoothness and regularity of the surface.

30. Flavor • Flavor is a property which is largely due to the stimulation of the chemical senses of :he consumer, both of taste and smell. • Minor contributions to the overall sensation of flavor nay also be made by receptors concerned with temperature and touch, but taste and smell re the dominant aspects of this most subjective of all quality attributes.

31. Texture • The term texture, as applied to a fruit or a vegetable, has been interpreted very broadly to include certain features of appearance and of “hand feel” in addition to the textural characteristics experienced during the actual eating of the fruit or vegetable. • In the present context, the word texture will be used to cover only those properties which are perceived by the sense of touch in the mouth.

33. V. NONDESTRUCTIVE QUALITY EVALUATION • Fruits, vegetables, and their products are more complex, primarily due to the fact that they are available in several forms, from freshly harvested produce to processed products of several types. • It is difficult to use the same method or principle for quality control through all these stages, and often times several methods need to be employed for quality control of different by-products of the same

35. A. MATURITY AND RIPENESS EVALUATION • The ripentng or maturity of fruits and/or vegetables is associated with changes in color, flavor, and texture that lead to the state at which the fruit or a vegetable is acceptable to eat. • The readily apparent phenomena associated with the ripening and maturity of most fruits and vegetables include changes in color,

37. B. DEVELOPMENT OF AUTOMATIC SORTING MACHINES • Most of the fruits and vegetables do not mature at the same time because of the biological and environmental variability. • The handpicking and sorting of only mature fruits necessitates a large labor force. • This represents a major expenditure in time and money to the fruit or vegetable grower.

39. C. DETECTION OF EXTERNAL AND INTERNAL DEFECTS • Fruits and vegetables can easily be sorted into different grades based on the differences in reflectance properties induced by external and internal defects including mechanical injuries that occur during harvesting and postharvest handling as well as certain microbial diseases.