Rice bolus texture changes due to α-amylase

- Mastication conditions influenced bolus texture changes during incubation at 37 °C.
- α-Amylase, not saliva uptake, caused decrease in rice bolus texture over 180 min.
- Influence of saliva amount on rice bolus texture differs in brown and white rice.

During mastication, starch hydrolysis caused by salivary α-amylase may influence food bolus formation and subsequent breakdown during gastric digestion. The objective of this study was to examine texture changes of rice boluses after simulated mastication. Boluses were prepared with three varieties each of brown and white rice (short, medium, and long grain). After simulated mastication, rice boluses were incubated from 0 to 180 min at 37 °C prior to texture measurement by bulk compression. Saliva was added at concentrations of 0.1 and 0.2 mL saliva/g rice. Boluses were also formed with 0.1 mL/g saliva without α-amylase. The peak force and area under the compression curve were significantly influenced by rice type, saliva level, and incubation time (p < 0.0001). The peak force of the boluses decreased, on average, from 127 to 52 N for brown rice and 111 to 54 N for white rice. Changes in bolus texture were described by a linear-exponential model. For all rice types, bolus texture was significantly lower in the presence of α-amylase. Saliva amount and presence of α-amylase influenced the textural properties of rice boluses during 180 min of incubation. These factors should be carefully considered in future in vitro studies of carbohydrate-based food products.