Modulating the glycaemic response of ready to eat extruded snack products utilising dietary fibre and fibre rich waste stream materials.

Brennan, Margaret Anne (2012) Modulating the glycaemic response of ready to eat extruded snack products utilising dietary fibre and fibre rich waste stream materials. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

The aim of this Ph. D. was to utilise commercial dietary fibre (DF) sources as well as DF from food waste streams to create snacks capable of reducing glycaemic response (GR). Obesity is a rising global epidemic due to changes in lifestyle, eating and exercise habits. Consumer demand for convenience has led to greater consumption of highly processed and refined foods so that even though cereal consumption is still high, many of the associated phytochemicals are removed, creating snacks high in energy and low in DF. High energy, low DF, diets have been linked to diabetes, certain types of cancer and heart disease. Health conscious consumers are demanding ‘healthy’ snack foods. In phase one DF rich products (at 5, 10 and 15 % w/w wheat flour replacement levels; total of 23 different samples) were incorporated into extruded snacks to determine the role of DFs in altering their physicochemical and nutritional characteristics. Starch digestion was shown to be lowered with all of high DF snacks (P ≤ 0.05), however, this was not always dose responsive (oat bran and super gum showed no difference with increasing concentrations). Product texture and viscosity parameters were also affected by DF although no general pattern could be observed. In phase two oat bran and psyllium material were incorporated into snack foods at 15 % (w/w) to evaluate potential GR in vitro and also in vivo (intervention study of 12 healthy subjects aged 18-40 yrs, with BMI 22.5-28, a total of 184 finger prick samples). Psyllium extruded snacks achieved attenuated in vitro and in vivo GR, (P ≤ 0.05). Oat bran reduced the in vitro but not in vivo response (P ≤ 0.05). Water absorption was negatively correlated with in vitro digestion (20 min) and in vivo AUC (P ≤ 0.05). In conclusion, the findings from this Ph. D. indicate the mechanism of DF ability to attenuate GR is related to its ability to bind water, and not all DFs behave in a similar fashion. Further research is required to elucidate the role of water in starch digestion and the impact on GR.