*Article*

## **Influence of** *Clitoria ternatea* **Flower Extract on the In Vitro Enzymatic Digestibility of Starch and Its Application in Bread**

#### **Charoonsri Chusak 1, Christiani Jeyakumar Henry 2,3, Praew Chantarasinlapin 1, Varanya Techasukthavorn 1 and Sirichai Adisakwattana 1,\***


Received: 21 May 2018; Accepted: 29 June 2018; Published: 2 July 2018

**Abstract:** This study aimed to assess the effect of the *Clitoria ternatea* L. flower extract (CTE), on the inhibition of pancreatic α-amylase, in vitro starch hydrolysis, and predicted the glycemic index of different type of flours including potato, cassava, rice, corn, wheat, and glutinous rice flour. The application in a bakery product prepared from flour and CTE was also determined. The results demonstrated that the 1% and 2% (*w*/*v*) CTE inhibited the pancreatic α-amylase activity by using all flours as a substrate. Moreover, 0.5%, 1%, and 2% (*w*/*v*) CTE showed a significant reduction in the glucose release, hydrolysis index (HI), and predicted glycemic index (pGI) of flour. In glutinous rice flour, 1% and 2% (*w*/*v*) CTE had a significantly lower level of rapidly digestible starch (RDS) and slowly digestible starch (SDS) with a concomitant higher level of undigested starch. The statistical analysis demonstrated strong positive significant correlations between the percentage of CTE and the undigested starch of wheat and cassava. The addition of 5%, 10%, and 20% (*w*/*w*) CTE significantly reduced the rate of starch digestion of the wheat bread. The pGI of bread incorporated with 5% CTE (*w*/*w*) was significantly lower than that of the control bread. Our findings sugges<sup>t</sup> that CTE could reduce the starch digestibility, the HI, and pGI of flour through the inhibition of carbohydrate digestive enzymes. Taken together, CTE may be a potent ingredient for the reduced glycemic index of flours.

**Keywords:** *Clitoria ternatea* L. flower extract; in vitro starch digestibility; hydrolysis index; predicted glycemic index
