Characterisation of pulse protein ingredients produced using different protein sources and processing technology, and potential for application in milk alternatives

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Vogelsang-O'Dwyer, Martin
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University College Cork
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In the face of the growing global population along with climate and food security concerns, there is currently much interest in developing plant protein ingredients from sustainable sources. Pulses are a valuable source of protein which could play an increased role in reducing our reliance on animal protein. Pulse protein ingredients can potentially provide the required functional properties (e.g., solubility, emulsifying, gelling, foaming) for a range of food applications. However, further development is necessary in order to increase our understanding and maximise the utility of pulse proteins as demand increases. This thesis addresses how protein source and processing can impact various properties of ingredients, including functional, nutritional and environmental aspects. In addition, the application of pulse proteins in high protein milk alternatives is examined. Furthermore, the impact of enzymatic hydrolysis on physicochemical and functional properties is explored. Protein isolates from blue lupin (Lupinus angustifolius) and white lupin (L. albus) were compared to assess the influence of protein source on various properties. Electrophoresis revealed major differences in molecular weight distribution. Solubility and foaming properties were similar for both isolates, while major differences in thermal gelling behaviour were found, with white lupin protein gelling at a lower concentration (7%) compared to blue lupin (23%). Both isolates were low in FODMAPs (fermentable mono-, di, oligosaccharides and polyols). In addition, the life cycle assessment (LCA) showed generally lower environmental impacts for the lupin isolates compared to milk powder per kg protein. Faba bean protein-rich flour (FPR) produced using dry fractionation was compared to faba bean protein isolate (FPI) produced using wet fractionation. Protein content of dry matter was lower for FPR (64.1%) compared to FPI (90.1%) Overall, superior functionality was found for FPR, including solubility and foaming properties. Wet processing (FPI) was found to be effective for removal of vicine, and trypsin inhibitors and FODMAPs. In the LCA, lower environmental impacts were found for FPR than FPI; however, both FPR and FPI had much lower impacts compared to milk powder. Milk alternatives were produced with blue lupin (BL) or white lupin (WL) protein isolate, with similar protein and fat content to low-fat cow’s milk. Both BL and WL milk alternatives had good colloidal stability and were suitable for low FODMAP diets. Increased homogenisation pressure (780 bar vs 180 bar) resulted in smaller particle size and increased stability for both BL and WL milk alternatives. WL milk alternative homogenised at 780 bar had the lowest separation rate, comparable to low fat cow’s milk, indicating good resistance to creaming. The effects of enzymatic hydrolysis on the physicochemical and functional properties of lentil protein isolate were assessed, in a comparison of three proteases. Hydrolysis with Alcalase or Novozym 11028 resulted in considerably higher solubility from pH 4–6, where the control showed poor solubility. Hydrolysis with Flavourzyme resulted in moderately increased solubility in this pH range, but slightly decreased solubility at neutral pH. Foaming properties were not impacted significantly by hydrolysis. Hydrolysis with Alcalase resulted in larger particle size and higher viscosity compared to the control. Overall, these studies provide useful insight into the properties of pulse protein ingredients which depend on pulse type and ingredient processing, modification with enzymatic hydrolysis, as well as their suitability for high protein milk alternatives.
Pulse protein , Functional properties , Lupin , Faba , Lentil , Processing , Milk alternative
Vogelsang-O'Dwyer, M. 2022. Characterisation of pulse protein ingredients produced using different protein sources and processing technology, and potential for application in milk alternatives. PhD Thesis, University College Cork.