Starch digestibility in phenolic-rich flours is modified by treatments that foster interactions with ferulic acid

Authors: FIECKE, CHELSEY - Arkansas Children'S Nutrition Research Center (ACNC); KALAMBUR, SATHYA - Pepsico; BHASKAR, AJAY - Pepsico; FERRUZZI, MARIO - Arkansas Children'S Nutrition Research Center (ACNC)

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Development of nutritional ingredients that aid in control of glycemic response is needed.Steeping pure starch ingredients (e.g., potato starch) in acidified water with ferulic acid reduces starch digestibility. We examined whether starch digestibility can be modified using this method applied to phenolic-flour ingredients (black rice, purple corn), which have potential for broader industry applications. Steeping phenolic-rich flour ingredients in acidified water with ferulic acid modifies starch digestibility, but is more effective when applied to pure starch ingredients due to losses of phenolic compounds from the phenolic-rich black rice and purple corn flours during steeping with acidified water.

Technical Abstract: Objectives: Formation of starch-ferulic acid complexes by acidic steeping with purified phenolics in model systems increases resistant starch content and reduces glycemic responses in animal models. We examined the potential to generate similar starch-phenolic complexes in phenolic-rich flours (black rice, BR; purple maize, PM) and assessed impacts to starch digestibility and phenolic bioaccessibility in vitro. Methods: Starch-phenolic complexation was performed using an acidic steeping method previously reported in pure starch-phenolic models [Li et al., Food Hydrocoll, 2018]. Potato starch and BR and PM flours (~4 g) were mixed with 0, 200, or 500 mg ferulic acid (FA) dispersed in HCl-acidified water (pH 2). After oscillation overnight, precipitates were washed three times with water and dried. Characterization of phenolic content in starting materials and post-treatment was carried out by UPLC-MS. In vitro starch digestibility was determined using starch hydrolysis curves from gelatinized samples and estimated glycemic index (eGI) and rapidly digestible (RDS), slowly digestible (SDS), and resistant starch (RS) content were calculated. Bioaccessibility of phenolics was determined from gelatinized samples using a three-stage in vitro digestion model. Results: Processing flours with acidified water resulted in a significant reduction in phenolic content (74-92%; p<0.0001) and an increase in starch digestibility. Steeping resulted in an increased RDS and eGI and decreased RS. Addition of FA to acid-steeped PM flours reduced eGI compared to acid treatment (p<0.0001), consistent with formation of starch-FA complexes. FA loading capacity on PS (60-77%) was greater than for PM and BR flours (11-28%), presumably due to presence of native phenolics in these ingredients. In PS and flour samples, increasing the amount of FA decreased FA bioaccessibility. The lowest FA bioaccessibility was found in potato starch samples with 500 mg FA (1-2%), while the lowest in the flours was for PM (14%). Conclusions: Acidified steeping with FA modifies starch digestibility, however this effect was greater in purified starch (e.g., PS) compared to phenolic-rich ingredients (e.g., PM or BR). Use of FA to modify starch macrostructure and/or digestibility in common flour ingredients may be limited by FA loading capacity and processing loss of native phenolics.