Measuring the Texture of Cooked Spaghetti. 2. Exploratory work on Instrumental Assessment of Stickiness and its Relationship to Microstructure

Abstract

A test cell comprising two flat plates, one of which was serrated, was used for measuring the stickiness of cooked spaghetti. The plates compressed 10 spaghetti strands to a preselected maximum force in an Instron, and were then held stationary to allow the spaghetti to relax and finally pulled apart. The maximum tensile force was used as an index of stickiness. Stickiness was independent of maximum compression force and the compression force after the relaxation period was linearly related to the maximum compression force, providing the maximum force did not rupture the spaghetti. Control of maximum force and force after relaxation depended on the rate of compression. Stickiness readings increased linearly with rate of plate movement and were also affected by the elapsed time after cooking.Standard test conditions were adopted: deformation rate (compression and tension) 10mm/min; maximum compression force 40kg; relaxation period 30sec; and the samples were tested 10min after cooking. The stickiness readings were not related to sensory ratings of adhesion because the effects of saliva were not simulated in the instrument but were related to assessments of stickiness prior to mastication.Examination of the microstructure of the cooked samples indicated that stickiness was related to the starch/protein ratio at the surface region of the spaghetti. A higher ratio was associated with sticky spaghetti while less sticky samples had lower ratios. It is not certain whether the differing ratios seen are due to changes in the starch or protein levels or both.