التقييم الحسي ل لأغذية Sensory evaluation of Food

1. التقييم الحسي للأغذيةSensory evaluation of Food المحاضر/ أ.د علي كامل الساعد رئيس الجمعية الأردنية للتقييم الحسي عضو الجمعية البريطانية للتقييم الحسي كلية الزراعة/الجامعة الأردنية ،عمان/الأردنemail :akamil@ju.edu.jo

4. Introduction • Sensory evaluation is commonly used in quality control and product development of food. • Sensory evaluation is made by the senses of taste, smell, vision , touch and hearing • When the food is eaten, the complex sensation that results from the interaction of our senses is used to measure the food quality

5. Objective &Subjective methods • Food quality can be measured either objectively by using instruments like determination of protein using Kjeldahl method, or objectively by using people in the sensory evaluation method • The importance of sensory analysis has grown more and more inspite of the availability and widespread of highly sensitive measuring instruments such as HPLC, GC, AAS …etc

6. Comparing instruments with sensory tests • Presently, food analyst are certain that optimal measurement of food quality can be achieved by coordinating between instrumental and sensory evaluation • In the instrumental analysis, there is a limit where no signal appears such as 1 ppm • While human senses which can be called biological detectors may still perceive an odor or taste which has a concentration less than 1 ppm

7. Comparing instruments with sensory tests • The instrument can analyse only one component while human senses can give a total impression of aroma, taste and texture • Accordingly, sensory analysis is very important and equals if not superior to the instrumental methods in the field of food product development

8. History • Modern sensory analysis started only before 70 years in the Scandinavian countries (1940) • Ten years later (1950), the European countries used the sensory analysis in their food firms • By 1970, sensory analysis developed into a science. It is now being taught in many European and American universities. University of California at Davis as example offers a degree program in sensory analysis • Many food firms in the west offer industrial courses in sensory analysis for their employees

9. Establishing of sensory groups • Establishing of scientific sensory groups started only before about 15 years (1999). • The 1st one was established in UK by The Institute of Food Science &Technology. • There are special conditions to be a member in • such sensory groups. • These sensory groups aim at dissemination of food sensory evaluation culture through workshops, seminars and conferences • Fortunately, the Jordanian Sensory Group is being established these days and it is expected to start its activities very soon.

10. Sensory groups

11. Sensory groups

12. Sensory groups

13. الجمعية الأردنية للتقييم الحسي للأغذية

15. ISO and Sensory evaluation • The International Standard Organization (ISO) started before about 20 years, standardization of the sensory testing methods and a significant work has been achieved. • Good and reliable sensory results can be obtained and analyzed statistically only if exact and standard scientific sensory testing methods are applied.

16. Terms related to sensory analysis: • Panelists: persons who test the food and judge it is named panel, panelist, assessors or judge. Panelist may be one person or several hundred depending on the type of the sensory evaluation method. • Testing Area: A special room or lab should be designed for carrying the sensory tests. This room should have partitions to separate panelists and has suitable stools, proper lighting, openings and a source of water. • The proper testing time was found to be later morning or mid afternoon.

17. Sensory laboratory

18. Sensory laboratory

19. Sensory terms • Sample preparation for sensory evaluation : • Kitchen: a well equipped kitchen is necessary to prepare food samples for sensory evaluation. • Number of samples to be given, time or duration between offering samples, soaking or using water…etc. are important factors that should be taken into consideration. • Selecting the proper panel test and in this respect, we have many tests where each one suits a special purpose, among the different panel tests we have : • Uniformity in samples is important,

20. Serving temperature should be selected properly according to the type of food. For beverage a temperature of 10-15 ºC is suitable while for ice cream a temperature of -1 ºC is recommended. In hot food like hamburger a temperature of 60 ºC is adviced. • Containers:colorless or white , identical containers should be used for each sample to be tested. Disposable paper or plastic containers are preferable. • Quantity of sample, in the case of difference test, this quantity is 16 ml for liquid or about 28 g for solid , and in preference test the quantity is doubled.

21. Sensory terms • Number of sample to be tested by panelist, it is is variable and depends on the type of the food to be tested and the experience of panels. However, a preliminary test should be conducted to determine how many samples can be given to the panelists to evaluate them properly. • Coding which means giving a code or a number to the samples to be tested is important and should not affect the results. It is not recommended to give numbers like 1, 2 or A, B ; but it is better to code the samples with a three digits numbers.

22. Sensory terms • Rinsing is also a step in sensory testing, it is recommended to rinse your mouth with worm water after testing fatty foods; in cheddar cheese it is adviced to rinse with water , then to wait 5 minutes before testing the next sample . • Information about the sample: little information should be given about the sample to be tested , otherwise the decision of the panels will be affected by these information. For this reason the persons involved in the preparation of the tested samples should not be included in the test.

23. Sensory terms • The panelists can be grouped to • trained panelists, • semi trained panelists and • untrained panelists. • In case of trained panelists a number of 4-5 is enough for the test, • while for semi trained a number of 10-20 is preferable and • for untrained person, the larger the best. • Panelist should be of good health and should stop smoking, eating and drinking before 30 minutes of the test. The panelists should be trained.

24. Sensory Quality Attributes • Food quality which can be detected by our senses can be divided to 3 main factors: • Appearance factors • Textural factors • Flavor factors • Appearance factor can be judged by sight and touch senses. They include size, shape, pattern, wholeness, damage and defects.

25. Sensory Quality Attributes • Appearance factor also includes color, glossy, transparency, turbidity and consistency (gel, flow, viscosity and spread) • Textural factors include the food properties which can be judged by both mouth feel and hand feel. • Mouth feel properties include chewiness, fibrousness, gritteness. Mealiness and stickiness. • Hand feel properties include the softness, firmness and juiceness.

26. Sensory evaluation and quality of food • Sensory evaluation is considered one of the most important tools used in measuring food quality. • There are some quality parameters that can not be measured accurately by instruments and the role of instruments is complementary to sensory evaluation. • Examples for such situation are the different tastes and odors. • Accordingly, we will focus on some quality parameters that have to be measured sensorial.

27. Sensory terms • There are a special sheets or questionnaire for each sensory test, the results should be tabled and analyzed statistically to find if there is a significant difference or not. • Factors affecting sensory evaluation: • expectation error (more information. • Logical error (yellow color in potato) • Suggestions. • Contrast effect (poor or good sample). • Stimulation error (other variables). • Halo effect (more than one factor) . • Motivation (importance). • Positional (bias i.e. very simple different and selection the middle sample).

28. Sensory Quality Attributes • Flavor factors quality parameters can be judged by the two senses taste and smell. • Under taste, we can find the terms salty, sour, bitter, and sweet. • Under odor , we can find the terms acid, burnt and fragrant. • Under the off-flavors we can find the terms over-cooked, stale, enzymatic, chemical and contaminated.

29. Sensory Quality Attributes • Flavor factors (taste and odor) are subjective and difficult to be accurately measured. • It is possible to find hundreds of descriptive terms regarding flavor depending on the type of food.

30. Complexity of flavor factor • Flavor in food is very complex, • an example is coffee flavor where more than 600 compounds responsible for coffee flavour have been separated and identified • and inspite of the great progress in the analytical instrumentation in this field like the use of gas chromatography techniques in identifying the flavor components, • flavor of food still a complex subject and not yet fully understood, specially with regard to the response of buds on the tongue to the different tastes.

31. Flavor factors are subjective • Flavor factors include taste and odor (smell, aroma) and can be detected by either tongue or nose. Taste and odor are largely subjective and as a result hardly to be accurately measured. • Subjective: can be described as sweet… etc. • Objective: can be measured and take a value as in ash, protein…etc. • Since flavor factors are subjective, there is a large possibility for difference of opinion regarding evaluation. However this is expected due to: • People differ in their sensitivity to detect taste and odor. • If they detect them correctly, people differ in their preference.

32. Effect of color and texture on the flavor • Another thing which is important here is the effect of color and texture on the flavor of the food. During evaluation of flavor, color, and texture often interfere with the evaluation of the flavor. • As an example flavor of chery and strawberry is associated by people with the red color. Also people frequently judge the thicker food (texture) as richer in flavor.

33. Methods for measuring flavor • Panel Tests or Taste Panels • Measuring Flavor: • Volatile material by GC • Flavor contributing substances by chemical and physical means as: sugar, salt and acid.

34. Measuring flavor of food • All these are research quality tools, but when it comes to the consumer quality acceptance, the above chemical, physical, and instrumental methods, can not work. The only means is to measure the quality using people. • Measuring flavor of food: • We have to use the panel tests; in conducting panel tests, many points should be considered such as the panelists or judges: their number, trained or semi-trained or untrained; testing room: the light, color of tables, chairs, ventilation and so on.

35. Methods for Sensory Evaluation • Many methods for sensory evaluation are available but the food quality control or product developer should be familiar with the advantage and disadvantage of each method and should select the method which properly suit the property to tested or examined in the food. • Sensory evaluation methods can be classified to 3 groups as follow: • Difference test. • Preference tests. • Descriptive tests.

36. Methods for Sensory Evaluation • Difference tests include the following methods: • Triangle test • Duo-Trio test _ Simple paired comparison test. • Scheffe paired comparison test • Multiple paired comparison test. • Ranking. • Scoring. • Ratio-scaling. • Each of the above methods is applied for certain evaluation test and has its own method of data analysis.

37. Methods for Sensory Evaluation • Descriptive Test: • Flavor profile test. • Texture profile test. • Preference Tests: • Paired comparison and Multiple compression preference tests. • Ranking • Hedonic scale test

38. Choosing the proper panel test • - Hedonic scale tests • - Triangle tests. • - Multiple comparison test. • - Ranking test: taste the following food samples and arrange them 1st, 2nd. 3rd and so on according to your preference. • Collecting sheets, tabulating, statistical analysis and giving conclusions. • These tests are applicable not only for evaluation of flavor factor but also for other food quality factors.

43. 1st labRecognition test for the four basic tastes

50. Recognition test for the four basic tastes • Our senses of odor or smell and taste are as important as our senses of vision and hearing regarding the test sensation. • Tongue and the hard palate are of interest for such sensation. • The four basic tastes are sweet and it is sensed at the tip of the tongue salty or saline are sensed at the tip and edge of the tongue, the third taste is the sour and it is sensed at the edge of the tongue. The fourth taste is the bitter and it is sensed at the back of the tongue .