Utilization of pulse protein-xanthan gum complexes for foam stabilization: The effect of protein concentrate and isolate at various pH

The present study examines the foaming behavior of pea and faba bean protein concentrates and isolates and explores the impact of pH and protein-polysaccharide complexation on overrun and foam stability. Foams were prepared with 5 wt% proteins with and without 0.25 wt% xanthan gum (XG) at pH 3, 5, 7 and 9. Most foams were unstable without XG. With XG foaming properties of protein concentrates were better than isolates. Irrespective of protein type and content, all protein-XG foams at pH 3 destabilized due to large insoluble complexes, however, at pH 5 foams were stable due to smaller size of insoluble complexes. Both the protein concentrate-XG foams were stable at pH 7 and 9 due to optimum viscosity and surface tension of the soluble complexes. Overall, the study revealed that the overrun and stability of pulse protein foams can be significantly improved by adding XG and controlling their intermolecular interactions as a function of pH.

Oleogelation using pulse protein-stabilized foams and their potential as a baking ingredient

Structuring liquid oil into a self-standing semisolid material without trans and saturated fat has become a challenge for the food industry after the recent ban of trans fat by the US Food and Drug Administration and Health Canada. Lately, the use of hydrocolloids such as animal proteins and modified cellulose for oleogel preparation has gained more attention. However, plant proteins have never been explored for the development of oleogels. The present study explored the use of freeze-dried foams prepared using protein concentrates and isolates of pea and faba bean with xanthan gum at different pH values for oil adsorption and subsequent oleogelation. Compared to protein isolate stabilized foams, protein concentrate-stabilized foams displayed (i) higher oil binding capacity (OBC) due to a higher number of smaller pore size; and (ii) lower storage modulus and firmness due to the higher oil content. At all pH values, there was no significant difference between the OBC of different protein isolates, but among the concentrates, pea displayed higher OBC than faba bean at pH 5 and faba bean displayed higher OBC than pea at pH 9. Results showed that such oleogels could be used as a shortening alternative. Cakes prepared using the pea protein-based oleogel at pH 9 displayed a similar specific volume as that of shortening-based cake, although with higher hardness and chewiness.

Canola oil was structured into oleogels using freeze-dried foam made with pea or faba bean protein concentrates or isolates and xanthan gum at pH 5, 7 and 9. The oleogels were used to bake cakes and compared with conventional shortening-based cakes.

Effect of protein type, concentration and oil droplet size on the formation of repulsively jammed elastic nanoemulsion gels

Rheology of sodium caseinate (SC) and whey protein isolate (WPI)-stabilized nanoemulsions (NEs) was investigated as a function of protein (1-5 wt%) and oil (30 and 40 wt%) concentration and storage time. For SC NEs, gel strength increased with an increase in protein and oil concentration and a decrease in droplet size and below a critical size transformed into a strong elastic gel that did not flow under gravity. Surprisingly, WPI NEs, although stable and had similar droplet size to SC NEs, did not form elastic gels. The stability of the NEs was studied for 3 months, and no significant change was observed. Considerable higher storage modulus (G') of SC NEs compared to WPI NEs was attributed to an increased effective droplet volume fraction (φeff) due to a thicker steric barrier of SC compared to WPI. The DLVO interdroplet potential was used to calculate the thickness of the charge cloud at an overall repulsive interaction of 1 kBT, which was added to the steric barrier to calculate the effective droplet size and φeff. At the highest φeff (0.79) for 5% SC NEs with 40% oil, the nanodroplets and associated repulsive barrier randomly jammed, leading to the formation of a strong elastic gel. For WPI NEs, maximum φeff was 0.57, leading to a lack of jamming and viscous fluid-like behaviour. Re-plotting G' with φeff for SC NEs with different protein concentration showed a linear trend followed by a rapid increase in G' at a critical φeff, confirming the transition from weak glassy region to strong randomly jammed structure. SC-stabilized repulsively jammed NE-gels could be used as a novel soft material where a lower oil volume fraction and long-term stability is required.

Salt and pH-Induced Attractive Interactions on the Rheology of Food Protein-Stabilized Nanoemulsions

This research aimed to investigate the possibility of forming gelled nanoemulsions (NEs) by inducing attractive interactions among the nanodroplets. The effect of salt concentration and changes in pH on the stability and gelation behavior of 2, 4, and 5% sodium caseinate (SC) and whey protein isolate (WPI)-stabilized 40% canola oil-in-water NEs were investigated. For the effect of salt, sodium chloride was added in a concentration of 0.1, 0.5, and 1 M in the continuous phase of the NEs at neutral pH, whereas to study the effect of acidification, the pH of the NEs was adjusted to the isoelectric point (pI) of the proteins. The addition of salt led to attractive gelation in WPI NEs because of a screening of charge. In contrast, the gel strength of SC-stabilized NEs was reduced with salt, which was attributed to the loss of close packing of droplets and their surrounding repulsive barriers because of charge screening and to the steric barrier of interfacial SC preventing droplet aggregation. All the NEs with pH at the pI of proteins transformed into strong attractive gels made of droplet aggregates irrespective of the type or concentration of protein because of the complete charge neutralization. The strength of the acidified NE gels increased with a decrease in droplet size and the type of protein used. Overall, research on the effect of different environmental factors on the stability and gelation behavior of protein-stabilized NEs could be useful for possible applications of these nanoscale materials in various food systems.

Oxidative stability of flaxseed oil: Effect of hydrophilic, hydrophobic and intermediate polarity antioxidants

Oxidative deterioration is a major issue limiting the utilization of flaxseed oil (FSO). Present study explored the effects of hydrophilic (tannic acid), hydrophobic (alpha-tocopherol), and intermediate polarity (ascorbyl palmitate) natural antioxidants, which displayed highest DPPH radical scavenging and iron chelating abilities among several others, on the oxidative stability of FSO. A synthetic antioxidant (TBHQ) was also used as a control. FSO oxidation was examined by peroxide and p-anisidine values during 30-day storage at 25, 40 and 60 °C, and by accelerated oxidation using a rancimat at 110 °C. On mass concentration basis, all natural antioxidants were less effective than TBHQ. Irrespective of the polarity, all natural antioxidants, except alpha tocopherol, delayed primary and secondary oxidation, and increased the oxidative stability index. The alpha-tocopherol displayed pro-oxidant effect at all concentrations. Rather than polarity, antioxidant capacities, and their ability to replace minor components from the oil-water interface were crucial for the protection of FSO.