The application of Differential Scanning Calorimetry to the gelatinisation of concentrated starch/water suspensions produced a well‐defined endotherm under suitable conditions. Measurement of the peak area enabled the heat of gelatinisation to be calculated. The method has been applied to the following aspects of gelatinisation: — 1 Intercomparison of different starches, 2) Effect of granule size, 3 Application to wheat flour, 4 Effect of starch damage, 5 Staling of starch gels, 6 Amylose and amylopectin.

SUMMARYField‐caged and open‐plot populations of the aphid Sitobion avenae on winter wheat (cv. Maris Widgeon) were sampled approximately twice‐weekly in the summer of 1978. Cage populations began at growth stage 10.2 (Feekes scale) (Zadoks, G. S. 52); they were removed by spraying with pirimicarb at growth stages 10.54 (71), 11.1–11.2 (77) and 11.2–11.3 (85) respectively. All cage populations reduced mean weight per grain but the effect per aphid unit was lowest in the population of longest duration. Although the aphid index in the open plots was higher than that in the early cage treatment, yield was unaffected. Cage infestations affected the breadmaking quality of the grain: percentage flour extraction was reduced and there was an increase in colour, nicotinic acid content and thiamine (vitamin B1) content of the flour; percentage nitrogen in the flour was unaffected but there was a reduction in baking value and in the high molecular weight glutenin content; infestation also reduced α‐amylase activity. Different aspects of grain quality did not change in parallel with one another or with yield changes and thus damage thresholds will vary according to the yield/quality measure under consideration.

The techniques of air classification, and differential centrifugation in non-aqueous media, have been combined t o isolate from flour ( a ) endosperm protein and (b) aleurone cell contents. The amino-acid composition of the isolated protein has been determined and compared with that of the total protein complex in the parent flour. The results show that in the isolated protein fraction the proportion of the glutenin/gliadin group of proteins is higher than in the parent flour. This was observed in the material obtained from both a strong and a weak flour. It is suggested that this partial segregation occurs in the air classification process. The protein fractions isolated from the weak and strong flours were closely similar in their overall amino-acid composition. The amino-acid composition of the protein contained in the isolated alenrone cell contents has also been determined. The composition is quite different from that of the main endosperm proteins and resembles, in this respect, some of the soluble protein fractions which have been previously isolated from flour. A notable feature of the composition is a relatively high content of arginine.

The relationship between two parameters of starch damage namely enzyme susceptibility and amylose extractability was examined in starch and in hard and soft flours ground by three unconventional methods. Variations in the relationship were as great in the starch series as in the flours, demonstrating that the effects of particle properties on the efficiency of one or other method of determination were not responsible. It is suggested that the two parameters are capable of independent variation since, in a single granule complete digestibility arises following a single "once for all" event, while for extractability that etent marks the beginning of a process which can be further increased by suitable treatment. Types of starch damage can be defined in terms of ratio between extractability and digestibility and micrographs are presented which display granules afflicted by different types of damage.

Methods have been devised for the isolation from wheat bran of (i) large fragments of aleurone layer, (ii) contents of aleurone cells, (iii) aleurone cell walls and (iv) aleurone granules. The structure of these preparations has been examined using the scanning electron microscope. Dimensions were generally smaller than those reported by workers using conventional microscopy of wheat sections, since. the latter were swollen by aqueous mounting. Although the polygonal prismatic cells varied in size and shape, an idealised cell could be described as a 35 pm cube, having walls of 2.5 pm thickness. Aleurone granules isolated from the cell contents, appeared to be spherical bodies ranging in size from 0.25 to 3.5 pm in diameter, the majority measuring about 2 pm. The granules were densely packed in a cementing matrix within the cell walls.