INTRODUCTIONStarch is widely used to build or modify the physical properties of many processed foods, and the effect of applying starch can only be revealed by being gelatinized. However, gelatinization by heating, particularly heating at a high temperature such as that involved in a retort treatment, produces extensive swelling and successive collapse of the swollen starch granules under physical stress accompanied by a drastic viscosity loss. Avoiding this problem by using augmented starch often results in a sticky and pasty texture and a decrease in the quality of starchy foods. Moreover, extensive swelling also produces a moist coating on fried foods, and results in rapid lost of crispness of the coatings due to water transportation from the internal food material after frying. It is thus very important to control the gelatinization behavior to inhibit swelling and maintain the resulting swollen starch granules.A number of studies have been carried out to investigate the effects of many coexisting substances and control the gelatinization behavior and swelling by the chemical and physical modification of starch. We have studied such control by adding amino acids, particularly, charged amino acids and charged amino acid-rich peptides, 1 8) and by conjugating or compounding non-starchy substances.9 12) We have clarified that such charged amino acids as lysine (Lys) and glutamic acid (Glu) strongly elevated the gelatinization temperature, and reduced the viscosity and swelling of potato starch (PS), 1,2) depending on the binding strength of the amino acid to the starch chains.3) It has also been revealed that adding charged amino acids could improve the degraded viscosity of retorted starch paste during storage.13) However, such control by adding amino acids and peptides is insufficient, because changes in such conditions as pH, salt concentration, temperature, and additives occurring during practical food processing would have varied effects and result in unstable control of starch. It has recently been reported that compounding with Glu, 9 11) and conjugating with fatty acylated saccharide through Lys 12) by simultaneous modification with a heat-moisture treatment and the Maillard reaction increased gelatinization temperature, decreased solubility and swelling, endowed thermal resistance, and easy vaporization, reduced the digestibility with α-amylase, and reduced the viscosity of a wheat flour paste. However, since these modifications are performed under such severe condition as 120 C for 60 90 min, there is the possibility of producing unfavourable side reactions. It is thus desirable for the swelling of starch to be controlled for food use by such a mild treatment as enzymic modification. One of the Abstract: Oleyl potato starch (OA-PS) was prepared by lipase-catalyzed solid-phase synthesis. PS retaining AY-Amano 30G as a lipase (PS/Lip) was prepared by immersing in the lipase solution, and by dehydrating with ethanol before air-drying. PS/Lip and oleic acid (OA) were incubated in n-hexane or without a sol...
