There have been many attempts in the past to assess objectively all those physical properties of a food product which are variously described as texture, toughness, shortness, etc. In the baking industry such objective testing is even more important than in most, as the properties of the products
FLOUR CONFECTIONERY
change with time (staling) and eventually become unacceptable (end of shelf-life). It follows therefore that a rapid method of testing is required for two reasons: (1) to produce a sufficient number of results for statistical treatment and (2) to produce those results in a period of time during which the staling change can be regarded as negligible.
Recorder via control box
A
¿ A d1 -" ^-Insulal
ΠΠΠ—
guides Insulated Compression -blockSample
Compression platform
Variable speed 3-27rev/min
FIG. 5. Shear and compressibility apparatus.
3 0
End
0 10 20 30 40 50 0 Time (sec)
6 3
H3
10 20 30 40 50 Time (sec)
FIG. 6. Madeira cake, shear and compressibility tests. All slices of each cake, except crusts, were tested consecutively. The force peaks shown are in pairs, the first being the shear and the second the compression.
246
The testing device must simulate the act of chewing which is commonly regarded as a combination of compression and of shearing (biting). To that end an instrument has been developed45 capable of making ten compressibility and shear tests a minute or twenty compressibility tests in the same time.
6 h
5 h
~ 4 h
2 h
Fresh End
After 3days
End End
0-5 Time (min)
1-0 0-5
Time (min) 1-0
FIG. 7. Bread, rapid compressibility tests. All slices of each loaf, except crusts, were tested consecutively.
The device which is illustrated diagrammatically (Fig. 5) consists of a compression platform capable of being raised and lowered mechanically by a rotating cam. On the platform is placed the sample, e.g. 1 cm thick sliced Madeira cake, between two Perspex plates in which are two aligned circular holes slightly larger than the compression block. When the compression platform is raised the compression block first shears the sample and then compresses it against the platform. The force thereby applied to the compression block is transmitted to a strain gauge which feeds a high speed recorder with a signal proportional to that force. A switch device ensures that the recorder chart moves only when tests are being made. When compressibility only is required to be determined the slices of sample may be passed under the
compression block without the Perspex plates. The use of different com-pression blocks and lifting cams add to the versatility of the instrument.
The type of results obtainable with Madeira cake is illustrated in Fig. 6 in which the first peak in each curve represents the shear force and the second the force resulting from the compression of a 1 cm thick slice to 0-5 cm.
Figure 6 shows the difference between the end slices and those in the middle of the cake and also the very significant "staling" effect by testing after different periods of time (4 hr, 1 and 5 days).
8 7
<u 6
"JÉ σ <υ
3
2 3 4 5 6 7 Moisture content (%)
FIG. 8. Rich Marie biscuits, snap tests at different moisture contents.
Typical results obtainable when only compressibility is required to be measured are illustrated in Fig. 7, but in this case using sliced bread. Here again significant differences are shown between the end (outside) slices and those in the middle of the loaf, due no doubt to the former being less moist.
The results also show the difference between a fresh loaf and a similar one after 3 days.
The instrument has also been applied to the testing of the shortness and brittleness of biscuits. An indication of the type of results obtainable is given in Fig. 8.
REFERENCES
1. Falconer, R. (1960). In: "Quality Control of Food", p. 107. Monograph No. 8, Society of Chemical Industry, London.
2. Wrinkle, C, Weiser, H. H. and Winter, A. R. (1950). Food Res. 15, 91.
3. Ministry of Agriculture Fisheries and Food and Ministry of Health (1963).
" The Liquid Egg (Pasteurisation) Regulations", S.I. 1503. (H.M.S.O., London), 4. Shrimpton, D. H., Monsey, J. B., Hobbs, B. C. and Smith, M. E. (1962). /.
Hyg., Camb. 60, 153.
5. British Egg Marketing Board (1962). "The Production of Prime Quality Lion Brand Pasteurised Liquid Whole Hen Egg." (Cyclostyled).
6. Stewart, G. F. and Kline, B. W. (1941). Proc. Inst. Fd. Tech. 48.
7. Kline, L., Sonoda, T. T. and Hanson, H. L. (1954). Food Tech., Champaign 8.
343.
8. Kent-Jones, D. W. and Amos, A. J. (1957). "Modern Cereal Chemistry"
(p. 367). (Northern Publishing Co., Liverpool).
9. Tucker, J. (1959). Am. Miller Processor 87, No. 12, 12, 16.
10. Mendelsohn, S. (1939). "Baking Powders." (Spon, London).
11. Learmonth, E. M. (1959). Food Manuf. 34, 314.
12. Bushill, J. H. and Wright, W. B. (1964). /. Soc. Dairy Technol. 17, 131.
13. British Standards Institution (1960). B.S. 3210.
14. Food and Agriculture Organisation/World Health Organisation (1963).
"Specifications for Identity and Purity of Food Additives. Vol. II. Food Colours." (F.A.O., Rome).
15. Association of Public Analysis (1960). "Separation of Food Colours permitted by the Colouring Matters in Food Regulations 1957." (A.P.A., London).
16. British Food Manufacturing Industries Research Association (1963). Analyst, Lond. 88, 864.
17. Ministry of Agriculture Fisheries and Food and Ministry of Health (1962).
"The Emulsifiers and Stabilisers in Food Regulations", S.I. 720. (H.M.S.O., London).
18. Pohle, W. D. and Mehlenbacher, V. C. (1950). /. Amer. Oil Chem. Soc. 27, 54.
19. Williams, J. (1961). Food Manuf. 36, 436.
20. Knight, R. A. and Robb, J. (1959). Bull. Brit. Baking Ind. Res. Assoc. 70, 101.
21. Lea, C. H. (1962). In: "Symposium on Foods. Lipids and their Oxidation"
(H. W. Schultz, E. A. Day and R. O. Sinnhuber, eds.), p. 3. (Avi Publishing Co., Westport, Conn.).
22. Sullivan, B. (1946). In: "Enzymes and their Role in Wheat Technology" (J. A.
Anderson, ed.), p. 153. (Interscience, New York).
23. Lea, C. H. (1957). /. Sei. Fd Agrie. 8, 1.
24. Hutchinson, J. B. (1961). In: "Production and Application of Enzymes Prepara-tions in Food Manufacture", p. 137. Monograph No. 11. (Society of Chemical Industry, London).
25. Sylvester, N. D., Lampitt, L. H. and Ainsworth, A. N. (1942). /. Soc. Chem.
Ind. 61, 165T.
26. Gearhart, W. M., Stuckey, B. N. and Austin, J. J. (1957). /. Amer. Oil Chem.
Soc. 34, 427.
27. American Oil Chemists Society (1959). "Official and Tentative Methods", Cd.
12-57. (A.O.C.S., Chicago).
28. Ministry of Agriculture Fisheries and Food and Ministry of Health (1958).
"The Antioxidants in Food Regulations", S.I. 1454. (H.M.S.O., London).
29. Mol., J. J. (1961). Missefs "Zuivel" 67, 111.
30. Wood, E. C. (1961). Analyst, Lond. 86, 667.
31. Etheridge, J. H. (1956). Brit. Commun. Electron. 3, 234.
32. Prentice, J. H. (1954). Lab. Practice 3, 186.
33. Brabender, C. W. (1934). Cereal Chem. 11, 586.
34. Halton, P. (1949). Cereal Chem. 26, 24.
35. Müller, H. G. and Barron, L. F. (1958). /. Sei. Fd Agrie. 9, 638.
36. Jones, F. R. (1951). / . appl. Chem. 1, S. 144.
37. Landrock, A. H., and Proctor, B. E. (1951). Food Tech., Champaign 5, 332.
249 38. Mohr, W. and Koenan, K. (1953). Proc. 13th Int. Dairy Congr., The Hague 2,
493.
39. Mohr, W. and Bauer, K. (1937). Proc. llth World Dairy Congr., Berlin 2, 536.
40. Babcock, C. J. (1922). U.S. Dept. Agrie. Bull. 1075.
41. Blodgett, F. W. and Webster, R. C. (1959). Aerosol Age 4, No. 6, 20, 73.
42. England, C. W. and Mecham, C. M. (1936). Bull. Md. agrie. Exp. Sta. 393, 569.
43. Templeton, H. L. and Sommer, H. H. (1933). /. Dairy Sei. 16, 329.
44. Buddemeyer, B. D. and Gotti, J. A. (1963). Cereal Sei. Today 8, 227.
45. Babb, A. T. S. (1965). /. Sei. Fd Agrie. 16, 670.