Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2008
Publication Date: 6/15/2009
Citation: Mohamed, A., Harry O Kuru, R.E., Gordon, S.H., Palmquist, D.E. 2009. Phospholipids and poly(glutamic acid)/hydrolyzed gluten: interaction and kinetics. Food Chemistry. 114(3):1056-1062. Interpretive Summary: Natural polymer interactions in different systems are not addressed adequately in the literature. The key to understanding these interactions is to understand the effect of these polymers on each other. The interaction between wheat protein and phospholipids is the determining factor that governs the final quality of baked products. It is also important in designating different types of flours for the appropriate uses. Since wheat protein is difficult to solubilize, a model phospholipid and gluten system was used to study their interaction. The physico-chemical properties of phospholipids are well-studied and reported in the literature. This study will benefit wheat producers in choosing the best type of phospholipids in their breeding programs. The results of this work will help wheat breeders to focus on the type of phospholipid that has more interaction with gluten protein and thus helps in the production of wheat flours for specific uses. The interaction between the two components was shown to be strong. That is consistent with the baking studies where phospholipids are found to increase bread loaf volume. The study reported the magnitude of the interaction in different conditions.
Technical Abstract: The effect of poly (glutamic acid) (PGA) and Hydrolyzed wheat gluten (HG) on the thermal and kinetics properties of lysophosphatidylcholine (LPC) was determined using Differential Scanning Calorimetry (DSC). A model system containing 3, 6 and 10% PGA or HG was added to 40% LPC aqueous suspension. The data reported here showed reduced delta H values and smaller change in the peak temperature. This concurs with the hydrophobic nature PGA and HG. Lower delta H values not accompanied with changes in the peak temperature suggest some kind of penetration of PGA or HG into the LPC bi-layer but not enough to minimize the order of LPC vesicle structure. The evidence for that is clear in the ability of LPC to form vesicles in the course of cooling cycle. The calculated activation energy (Ea) of pure LPC vesicles disruption (heating) and formation (cooling) was 696.6 KJ / mol and 520.4 KJ / mol respectively. Overall, the trend of lower Ea in the presence of PGA was apparent, where PGA with higher molecular weight further reduced the Ea of LPC. In the presence of 3% HG, the drop in Ea was 152 and 106 K.J / mol for the heating and cooling cycles respectively. This showed the different behavior of LPC in the presence of HG versus PGA, where lower drop in Ea when compared to PGA for both heating and cooling cycles. The purported molecular interaction between phospholipids and gluten has been confirmed using FTIR spectroscopy. Infrared evidence of the interaction was observed in both the LPC/Gluten blend and in model mixtures consisting of LPC and PG of different molecular weights.