STUDIES ON RYE STARCH PROPERTIES AND MODIFICATION .3. VISCOGRAPH PASTING CHARACTERISTICS OF RYE STARCHES

Pasting characteristics of native as well as of physically and chemica lly modified rye starches have been characterized and compared with th e other triticeae starches and starches from maize and potatoes. Norma l and pressure viscograph techniques were applied. Additional, ridgeli metry investigation were performed with the gels formed from the visco graphically prepared pastes. Rye as well as wheat and triticale starch es exhibit unique, typical gelatinization behaviour, late onset of con sistency gain, low but highly stable cooking consistency, consistency gain of the two-threefold on cooling. Gels are of statistically lower firmness as those of maize starch. Higher degrees of consistency, good cooking stability and high consistency gain on cooling were achieved after treatment in the pressure viscograph (max. temp. 120 degrees C). Physical treatment like annealing, heat-moisture treatment, extractio n by aqueous solvents, drying procedures result in different but in ea ch case typical change of properties: shift of onset consistency gain, lower maximum consistency values, lower consistency gain on cooling. Gelfirmness will be enhanced in every case. The pasting characteristic s of heat-moisture treated wheat starch differ from this by remarkably higher consistency values. Possible reasons for this are discussed. S uccination (0.7-2.1%) changes the pasting characteristics towards the potato starch type, lower onset temperatures of consistency gain, very high values in maximum consistency, diminished cooking stability. The gels formed are smooth and turbid. Acetylation (0.7-2.3%) changes the pasting characteristics towards the maize starch type, maximum consis tencies are lower compared with succinated triticeae starches. Ac cont ents of 0.7% inhibit the formation of rigid gels.