2021 年 35 巻 1 号 p. 29-41
This paper reviews starch gel foods from the perspective of cookery science: warabi mochi (traditional sweet gel in Japan) and blancmange as hard gels and pastry cream/custard as a soft gel. Since warabi mochi is made from expensive warabi starch, physiochemical properties of several starches were tested as possible replacers. High potential of sago starch as a replacer was demonstrated as compared with sweet potato, potato, tapioca, and kudzu starches which are currently used as the replacers. Sago starch showed excellent characteristics in gel elasticity comparable to sweet potato and potato starches, high gel cohesiveness and low gel adhesiveness comparable to tapioca starch, and gel hardness comparable to kudzu starch. Toward quality improvements of warabi mochi, its preparation methods were also optimized. For instance, trehalose was added to suppress starch retrogradation in warabi mochi, and modified wheat starch was added to stabilize its gel quality. Meanwhile, warabi mochi is primarily a mixture of starches, sugars, and water, whereas most starch gel foods are mixtures of the primary ingredients and secondary ingredients such as proteins and fats. As for the blancmange, milk was replaced with soy protein isolate or soy milk powder for its quality improvement. For maximizing the physicochemical properties as well as taste, ratio of starch, protein, and fat was optimized by Scheffé’s simplex lattice design method: its triangular diagram clearly showed its optimal ratio for blancmange of high quality. Regarding pastry cream/custard, since its melting mouthfeel governs overall quality preference, methods to evaluate the melting mouthfeel were established. Thereafter, applicability of modified starches to pastry cream/custard was investigated to fit its texture to each food preparation. Based on physicochemical properties of the modified starches, pastry cream/custard preparation was adjusted to each of various food products.