Manipulating the Microstructure of Potatoes for Slow Starch Digestion

OBJECTIVES: Potatoes are nutritious foods that provide essential energy in the form of starch. However, numerous studies have shown that their consumption could lead to high postprandial glycemia. Our aim is to transform staple foods into a healthy diet with modulated postprandial glycaemia and sustained energy. METHODS: Potatoes were blanched in a 500 ppm calcium solution for 30 min at 70 °C prior to streaming. We wanted to study if blanching potatoes in the presence of divalent cations increased pectin-cross linking and could lead to a lower cell wall permeability to digestive amylolytic enzymes. Potatoes were submitted to in-vitro simulated gastrointestinal digestion. The digestion of starch occurred in the intestinal phase in the presence of digestive enzymes (1350 U of pancreatic amylase, 3500 U of glucoamylase and 200 U of invertase). Aliquots were obtained at time intervals to quantify glucose release. The diffusivity rate of dextran probes (20 KDa, 60 KDa, and 150 KDa) into isolated potato cells was determined by the fluorescence recovery after photobleaching (FRAP) assay. Texture profile analysis (TPA) was also carried out to quantify multiple textural parameters. RESULTS: Our treatment increased the slowly digestible starch fraction of potatoes from 10.5% to 35.3%. Treated potatoes had 40.7% and 99.9% lower cell wall diffusivity of 20 KDa dextrans and 70 KDa dextrans, respectively. These results show that a-amylase (∼59 KDa) access to starch within the cells was significantly lower in our treated potatoes. Thus, is the driving factor for the slower starch digestibility rate. These results are unexpected since a-glucosidase is the gatekeeper for starch hydrolysis. Texture analysis showed that treated potatoes possess desirable attributes such as higher hardness which could drive consumer preference. CONCLUSIONS: Developing slowly digestible staple foods, such as potatoes, is a promising approach for moderating glycemia as well as extending satiation and energy, and, in the long-term, control food intake and bodyweight. FUNDING SOURCES: This research was funded by A*STAR Biomedical Research Council grant IAF-PP (HBMS Domain): Food Structure Engineering for Nutrition and Health.