Characterisation and foaming properties of hydrolysates derived from rapeseed isolate

Oil-water interface and emulsion stabilising properties of rapeseed proteins napin and cruciferin studied by nonlinear surface rheology

HYPOTHESIS

Two major protein families are present in rapeseed, namely cruciferins and napins. The structural differences between the two protein families indicate that they might behave differently when their mixture stabilises oil-water interfaces. Therefore, this work focuses on elucidating the role of both proteins in interface and emulsion stabilisation.

EXPERIMENTS

Protein molecular properties were evaluated, using SEC, DSC, CD, and hydrophobicity analysis. The oil-water interface mechanical properties were studied using LAOS and LAOD. General stress decomposition (GSD) was used as a novel method to characterise the nonlinear response. Additionally, to evaluate the emulsifying properties of the rapeseed proteins, emulsions were prepared using pure napins or cruciferin and also their mixtures at 1:3, 1:1 and 3:1 (w:w) ratios.

FINDINGS

Cruciferins formed stiff viscoelastic solid-like interfacial layers (Gs' = 0.046 mN/m; Ed' = 30.1 mN/m), while napin formed weaker and more stretchable layers at the oil-water interface (Gs' = 0.010 mN/m; Ed' = 26.4 mN/m). As a result, cruciferin-formed oil droplets with much higher stability against coalescence (coalescence index, CI up to 10%) than napin-stabilised ones (CI up to 146%) during two months of storage. Both proteins have a different role in emulsions produced with napin-cruciferin mixtures, where cruciferin provides high coalescence stability, while napin induces flocculation. Our work showed the role of each rapeseed protein in liquid-liquid multiphase systems.

Functionality of Ingredients and Additives in Plant-Based Meat Analogues

Meat analogue research and development focuses on the production of sustainable products that recreate conventional meat in its physical sensations (texture, appearance, taste, etc.) and nutritional aspects. Minced products, like burger patties and nuggets, muscle-type products, like chicken or steak-like cuts, and emulsion products, like Frankfurter and Mortadella type sausages, are the major categories of meat analogues. In this review, we discuss key ingredients for the production of these novel products, with special focus on protein sources, and underline the importance of ingredient functionality. Our observation is that structuring processes are optimized based on ingredients that were not originally designed for meat analogues applications. Therefore, mixing and blending different plant materials to obtain superior functionality is for now the common practice. We observed though that an alternative approach towards the use of ingredients such as flours, is gaining more interest. The emphasis, in this case, is on functionality towards use in meat analogues, rather than classical functionality such as purity and solubility. Another trend is the exploration of novel protein sources such as seaweed, algae and proteins produced via fermentation (cellular agriculture).

Pepsin-Assisted Transglutaminase Modification of Functional Properties of a Protein Isolate Obtained from Industrial Sunflower Meal

The utilization of industrial sunflower meal to produce protein-rich products for the food industry is an alternative approach for better and more efficient use of this agricultural by-product. Sunflower meal proteins possess specific functional properties, which however need improvement to broaden their potential as supplements for delivering high--quality products for human nutrition. The aim of the study is to evaluate the combined influence of low-degree pepsin hydrolysis and transglutaminase (TG) modification on industrial sunflower meal protein isolate functionality at pH=2 to 10. Three TG-modified pepsin hydrolysates with the degree of hydrolysis of 0.48, 0.71 and 1.72% were produced and named TG-PH1, TG-PH2 and TG-PH3, respectively. All three TG-modified pepsin hydrolysates exhibited improved solubility at pH between 3.5 and 5.5 as the highest was observed of TG-PH3 at protein isoelectric point (pI=4.5). Sunflower meal protein isolate and TG-modified sunflower meal protein isolate had greater solubility than the three TG-modified hydrolysates at pH<3 and >7. Significant improvement of foam making capacity (p<0.05) was achieved with all three TG-modified pepsin hydrolysates in the entire pH area studied. Pepsin hydrolysis of the protein isolate with the three degrees of hydrolysis did not improve foam stability. Improved thermal stability was observed with TG-PH3 up to 80 °C compared to the protein isolate (pH=7). At 90 °C, TG modification of the protein isolate alone resulted in the highest thermal stability. Pepsin hydrolysis followed by a treatment with TG could be used to produce sunflower protein isolates with improved solubility, foam making capacity and thermal stability for use in the food industry.

Relevance of the Functional Properties of Enzymatic Plant Protein Hydrolysates in Food Systems

Proteins play a crucial role in determining texture and structure of many food products. Although some animal proteins (such as egg white) have excellent functional and organoleptic properties, unfortunately, they entail a higher production cost and environmental impact than plant proteins. It is rather unfortunate that plant protein functionality is often insufficient because of low solubility in aqueous media. Enzymatic hydrolysis strongly increases solubility of proteins and alters their functional properties. The latter is attributed to 3 major structural changes: a decrease in average molecular mass, a higher availability of hydrophobic regions, and the liberation of ionizable groups. We here review current knowledge on solubility, water- and fat-holding capacity, gelation, foaming, and emulsifying properties of plant protein hydrolysates and discuss how these properties are affected by controlled enzymatic hydrolysis. In many cases, research in this field has been limited to fairly simple set-ups where functionality has been assessed in model systems. To evolve toward a more widely applied industrial use of plant protein hydrolysates, a more thorough understanding of functional properties is required. The structure-function relationship of protein hydrolysates needs to be studied in depth. Finally, test model systems closer to real food processing conditions, and thus to real foods, would be helpful to evaluate whether plant protein hydrolysates could be a viable alternative for other functional protein sources.

Effect of three cations on the stability and microstructure of protein aggregate from duck egg white under alkaline condition

Pidan (alkaline egg) has been consumed widely in oriental countries and lead, a toxic element, has been used traditionally to yield the desirable characteristics. For safety concerns, alternative cations can be used for the production of pidan with comparable properties to traditionally prepared pidan. Turbidity measured as absorbance at 400 nm and microstructure of duck egg white proteins at pH 12 as influenced by three cations at various levels were investigated. Turbidity and particle size of egg white protein (20 g/kg) in 10 g/kg NaCl sample with CaCl2, PbO2 or ZnCl2 added at a level of 1 g/kg increased with time up to 1 h, followed by a decrease (p < 0.05). Nevertheless, the turbidity was retained more in samples added with PbO2, suggesting high stability of the aggregate formed. Zeta potential showed that the aggregates treated with PbO2 had a comparatively lower negative charge. Light microscopic studies indicated that the aggregation of egg white proteins was induced by ions but varied with the types of ions and incubation time. Therefore, PbO2 exhibited the highest stabilizing effect on egg white protein under alkaline condition. However, ZnCl2 can be used as an alternative compound even if it had lower impact on stability of aggregate of duck egg white protein.

Production, purification and characterization of serraticin A, a novel cold-active antimicrobial produced by Serratia proteamaculans 136

AIM

This study focuses on the production, purification and characterization of serraticin A, a novel cold-active antimicrobial produced by Serratia proteamaculans 136.

METHODS AND RESULTS

A Ser. proteamaculans strain producing a novel cold-active antimicrobial was isolated from Isla de los Estados, Argentina. Antimicrobial production was optimized in a BIOFLO 101 bioreactor under batch culture mode, with temperature, pH and dissolved oxygen controlled conditions. A purification protocol was developed including activated charcoal adsorption, solid-phase C18 extraction (SPE) and semi-preparative HPLC. The molecular weight was determined by LC/QTOF/MS/MS mass analysis.

CONCLUSIONS

Serratia proteamaculans 136 produces a cold-active low molecular bacteriocin-like compound named serraticin A. In this work, it has been laboratory-scale produced, purified and partially characterized. Cross-immunity test revealed that serraticin A is very different from other well-known microcins assayed, with a wide inhibitory spectrum, showing an interesting biotechnology potential to be applied as a control agent against pathogenic bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study is the first report of a cold-active compound with antimicrobial activity from Ser. proteamaculans. The work also highlights that cold environments could be a suitable source of micro-organisms with ability to produce cold-active biomolecules of biotechnological interest.

Differential Proteomic Analysis of Four Near-Isogenic Brassica napus Varieties Bred for their Erucic Acid and Glucosinolate Contents

Four near-isogenic B. napus varieties, with decreasing amounts of erucic acid and glucosinolates reflecting the actual breeding process, were used to characterize the proteins affected during this process. Following improvement of 2-DE conditions, proteins differentially accumulated were identified by mass spectrometry analysis. Accumulation of cruciferins was found to be only slightly affected, whereas significant quantitative differences were mainly found for proteins involved in defense system and carbohydrate metabolism.