Effect of Extent of Gelatinisation of Starch on the Glycaemic Responses of Carbohydrate Rich Breakfast Meals

Introduction: Previous studies have shown that roti and pittu, which are South Asian foods, when prepared with the same composition of wheat flour and coconut scrapings had significantly different (p<0.05) glycaemic index (GI) values. The only difference was in the processing where roti (GI 57) was dry-heated (roasted) and pittu (GI 80) was wet-heated (steam cooked). The present study was carried out to investigate the association between GI and the properties of starch during processing for the observed variations of GI values of roti and pittu prepared with different flour varieties. Methods: The characteristics of isolated starch granules, molecular size distribution pattern of carbohydrates, amylose, amylopectin contents and change in temperature during the cooking of ‘pittu’ and ‘roti’ were analysed. Results: The results indicate that the contribution to GI from starch gelatinisation correlates positively and corroborates with reported data. Thus the significantly low GI values of roti compared to pittu could be mainly attributed to less disintegrated and less swollen starch granules of flour used in the preparation of roti. This was observed irrespective of the variety of flour. Conclusion: This study confirms that wet heat gelatinises starch to a greater extent than dry heat and provides evidence of a possibility that foods processed using dry heat to be associated with lower GI values, than the wet processed foods if other factors are constant.

Total Phenol Content and Antioxidant Potential of Traditional

Introduction: According to folklore and Ayurveda, many tubers and flour made from various plant parts, traditionally used to made breakfast meals, are rich in nutrients and polyphenols. The objective of the study was to determine the total phenolics content (TPC) and antioxidant potential of some tubers and foods made with seeds and other plant parts. Methods: The TPC in the extracts was determined according to the Folin-Ciocalteu method (mg Gallic acid equivalents (GAE/100g FW) and antioxidant activity by 2, 2’–Azino–bis (3- ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS)cation free radical decolouration assay (􀂗mol/g Trolox equivalent antioxidant capacity; TEAC). Results: The TPC of raw and processed tubers ranged from 127-517 mg GAE/ 100g FW. Among the tuber varieties, Dioscorea alata, violet had the highest antioxidant potential. Among raw flour, Vateriaco pallifera had the highest phenolic content (1162) and lowest (79) was in Caryota urens. Antioxidant potential of raw and food prepared from indigenous flour ranged from 3-225􀂗mol/g TEAC with Vateriaco pallifera raw flour having the highest antioxidant potential (225􀂗mol/ g). Processing decreased both the phenolics and antioxidant potential significantly (P<0.05). A significant correlation was observed between polyphenolic content and antioxidant capacity in raw flour (r2=0.993). Conclusion: The traditional tubers and food prepared incorporating indigenous flour varieties are rich sources of phenols and antioxidants indicating their potential for utilisation in home food preparation and by the food industry.

Sri Lankan Rice Mixed Meals: Effect on Glycaemic Index and Contribution to Daily Dietary Fibre Requirement

Introduction: The glycaemic index (GI) concept ranks starchy foods according to the blood glucose responses following ingestion. When considering commonly consumed Sri Lankan meals, only a few can be categorised as low GI. However, a significant negative correlation between the GI of Sri Lankan meals and fibre content has been observed indicating the potential to reduce the GI of meals by incorporating naturally occurring sources of fibre. Thus, the objective of this study was to study the effect of increased edible quantities of fibre on the GI of rice meals consumed in Sri Lanka. Methods: Meal 1 consisted of rice with several meal accompaniments (lentil curry, boiled egg, coconut gravy and Centella asiatica (gotukola) leaves salad). Meal 2 contained similar constituents as meal 1 and a Lasia spinosa (kohila) rhizome salad. The composition of meal 3 was similar to meal 2 but contained Trichosanthes cucumerina (snake gourd) salad instead of Lasia spinosa salad. Meal 3 contained similar fibre contents as meal 1 and similar meal size as meal 2. The glycaemic indices of the three meals were determined with healthy individuals (n=10, age =20-30 yrs, BMI=24±3 kg/m2) using bread as the standard. Results: Meals 1 and 3 contained total dietary fibre (TDF) contents of 15.2g. Meal 2 contained 16.3g TDF. The GI values of the three meals were 63±5, 57±5, 61±5 respectively and were not significantly different from one another (p>0.05). The GI of the rice mixed meal 2 was reduced by 9% when total edible dietary fibre content of the actual meal was increased by 7.2%. Conclusion: The study results show that the GI of rice mixed meals may be reduced by including naturally occurring sources of fibre with starchy staples while fulfilling daily dietary fibre requirement of an adult at low cost.