SOME PHYSICAL-PROPERTIES OF BARLEY STARCHES FROM CULTIVARS DIFFERING IN AMYLOSE CONTENT

Thermal and viscous properties of four barley starches differing in amylose content (two normal and two waxy) were studied. The gelatinization enthalpies (ΔHG) of the waxy barley starches were high compared to other cereal starches, but the normal barley starches were similar to rye starches. The gelatinization temperatures (TG) were in the range 58·3-61·3°C, with the waxy starches showing the highest values. The transition enthalpies (ΔHex) of the amylose-lipid complex were 1·4-2·0 J/g for the normal barley starches but 0·6 J/g for the waxy starches. The transition temperature (Tex) was similar (108·8-109°C), except for the waxy starch WH 76 (105·3°C). The waxy barley starches retrograded to a greater extent than the normal barley starches. Their retrogradation kinetics were also different, as the waxy barley starches had a very slow retrogradation rate during the first days of storage. The extent of retrogradation of the waxy barley starches was similar to that of maize starch, but the retrogradation of the normal barley starches was comparable to rye starches. The waxy starches were most extreme in viscous properties at both concentrations studied. The WH76 starch had the lowest paste viscosity, and the barley-covered waxy starch (BCW) had the highest viscosity. The normal barley starches were similar to each other and had values between the waxy starches. © 1992, Academic Press Limited. All rights reserved.