An erosion-type hydrolysis behavior of insoluble protein fraction from Chlorella protothecoides.

BACKGROUND: Acid-induced hydrolysis of proteins has been used to improve the solubility and functional properties of various proteins, and could be a promising tool to facilitate the use of currently underutilized insoluble microalgae protein-rich fractions in food applications. However, the results of a prior study showed an unusual resistance of an insoluble microalgae protein-rich fraction to acid hydrolysis at room temperature. RESULTS: In the present study, the insoluble protein-rich fraction extracted from microalgae Chlorella prothothecoides was treated with 0.5 mol L-1 hydrochloric acid at 25, 45, 65 or 85 °C for 0-4 h. The results showed that hydrolysis of the fraction at 85 °C for 4 h led to decreases in the amount of insoluble protein-rich aggregates and the formation of fragments with a lower molecular weight, as well as an increase in protein solubility by approximately 40%. Nevertheless, some aggregated insoluble protein-rich particles remained, even after hydrolysis at 85 °C for 4 h. CONCLUSION: The higher temperature improved the efficiency of the acid hydrolysis of the insoluble protein fraction from microalgae Chlorella prothothecoides, which is highly acid-resistant. Overall, an erosion-based mechanism was suggested for the acid hydrolysis of insoluble microalgae protein fraction. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Physical, Chemical and Biochemical Modification Approaches of Potato (Peel) Constituents for Bio-Based Food Packaging Concepts: A Review.

Potatoes are grown in large quantities and are mainly used as food or animal feed. Potato processing generates a large amount of side streams, which are currently low value by-products of the potato processing industry. The utilization of the potato peel side stream and other potato residues is also becoming increasingly important from a sustainability point of view. Individual constituents of potato peel or complete potato tubers can for instance be used for application in other products such as bio-based food packaging. Prior using constituents for specific applications, their properties and characteristics need to be known and understood. This article extensively reviews the scientific literature about physical, chemical, and biochemical modification of potato constituents. Besides short explanations about the modification techniques, extensive summaries of the results from scientific articles are outlined focusing on the main constituents of potatoes, namely potato starch and potato protein. The effects of the different modification techniques are qualitatively interpreted in tables to obtain a condensed overview about the influence of different modification techniques on the potato constituents. Overall, this article provides an up-to-date and comprehensive overview of the possibilities and implications of modifying potato components for potential further valorization in, e.g., bio-based food packaging.

Bio-Based Packaging: Materials, Modifications, Industrial Applications and Sustainability.

Environmental impacts and consumer concerns have necessitated the study of bio-based materials as alternatives to petrochemicals for packaging applications. The purpose of this review is to summarize synthetic and non-synthetic materials feasible for packaging and textile applications, routes of upscaling, (industrial) applications, evaluation of sustainability, and end-of-life options. The outlined bio-based materials include polylactic acid, polyethylene furanoate, polybutylene succinate, and non-synthetically produced polymers such as polyhydrodyalkanoate, cellulose, starch, proteins, lipids, and waxes. Further emphasis is placed on modification techniques (coating and surface modification), biocomposites, multilayers, and additives used to adjust properties especially for barriers to gas and moisture and to tune their biodegradability. Overall, this review provides a holistic view of bio-based packaging material including processing, and an evaluation of the sustainability of and options for recycling. Thus, this review contributes to increasing the knowledge of available sustainable bio-based packaging material and enhancing the transfer of scientific results into applications.

Quillaja Saponin Characteristics and Functional Properties.

Consumer concerns about synthetically derived food additives have increased current research efforts to find naturally occurring alternatives. This review focuses on a group of natural surfactants, the Quillaja saponins, that can be extracted from the Quillaja saponaria Molina tree. Quillaja saponins are triterpenoid saponins comprising a hydrophobic quillaic acid backbone and hydrophilic sugar moieties. Commercially available Quillaja saponin products and their composition and properties are described, and the technofunctionality of Quillaja saponins in a variety of food, cosmetic, and pharmaceutical product applications is discussed. These applications make use of the biological and interfacial activities of Quillaja saponins and their ability to form and stabilize colloidal structures such as emulsions, foams, crystallized lipid particles, heteroaggregates, and micelles. Further emphasis is given to the complexation and functional properties of Quillaja saponins with other cosurfactants to create mixed surfactant systems, an approach that has the potential to facilitate new interfacial structures and novel functionalities.

Shear rheological properties of acid hydrolyzed insoluble proteins from Chlorella protothecoides at the oil-water interface.

Microalgae are promising protein sources due to their overall high protein content. The low aqueous-solubility of microalgae proteins, however, limits their application in food, pharmaceutical or personal care systems, unless solubility is enhanced by e.g. hydrolysis. In this study, we examined the interfacial rheological properties at the oil-water interface of insoluble microalgae protein-rich fraction from Chlorella protothecoides and their hydrolysates prepared by hydrolysis in hydrochloric acid at 65 °C (Hydrolysates 65) and 85 °C (Hydrolysates 85). Results showed increased interfacial activity of the insoluble microalgae protein-rich fraction after hydrolysis: Hydrolysates 65 and Hydrolysates85 had higher interfacial storage Gi' and loss moduli Gi″ compared to the untreated insoluble microalgae protein-rich fraction. Increasing amounts of soluble protein fragments mixed with insoluble protein particles in hydrolysates stabilized interfacial layers. The influence of pH on the interfacial behavior of samples was also determined and revealed that Gi' and Gi″ values of treated and untreated protein fractions decreased as pH increased beyond their isoelectric points due to increasing electrostatic repulsions between adsorbed protein fragments and aggregates. The high viscoelasticity of the acid-hydrolyzed insoluble microalgae protein-rich fraction at the oil-water interface indicates a high potential for them to be useful in stabilizing emulsion-based products.

Concentration effect of Quillaja saponin - Co-surfactant mixtures on emulsifying properties.

HYPOTHESIS: This study examined the emulsifying properties of mixed surfactant systems of Quillaja saponins and food-grade co-surfactants (Na-caseinate, pea protein, rapeseed lecithin, and egg lecithin). We hypothesized to these mixtures may build mixed adsorption layers and thus enhance emulsion stabilization. EXPERIMENTS: Oil-in-water emulsions (10%, pH 7) were prepared with different concentrations of co-surfactants (0.1-5.0%) alone or mixed with Quillaja saponins (0.05 or 0.5%). Dynamic interfacial tension measurements were performed to characterize the behavior of the surfactants at an oil-water interface. FINDINGS: Low Quillaja saponin concentrations led to either no changes or substantial increases in particle sizes of protein stabilized emulsions, but d43-values decreased in lecithin stabilized emulsions at low lecithin concentrations. The dominating effect of Quillaja saponins at high concentrations led to formation of small droplets (d43≤2 µm) in all emulsions, except with 2.5% pea proteins. All co-surfactants showed synergistic or additive effects with respect to interfacial tension reductions upon addition of Quillaja saponins (except for egg lecithin with 0.005% Quillaja saponin addition). The results indicated a competing effect for saponin-protein interfaces, but formation of mixed saponin-lecithin interfaces, thus showing that the emulsion stabilization and interfacial properties can be tuned by specific binary surfactant mixtures.

Inhibitory effect of phosphates on magnesium lactate efflorescence formation in dry-fermented sausages.

This study aimed to prevent the phenomena of efflorescence formation on the surface of dry fermented sausages due to the complexation of efflorescence forming cations with phosphates. Efflorescence formation is a critical issue constituting a major quality defect, especially of dry fermented sausages. Different phosphates (di- and hexametaphosphate) were added (3.0g/kg) to the sausage batter. As a hypothesis, these additives should complex with one of the main efflorescence-causing substances such as magnesium. The formation of efflorescences was determined for dry fermented sausages without phosphate addition, with diphosphate, or hexametaphosphate addition during 8weeks of storage under modified atmosphere. The visual analyses of the sausage surface revealed high amounts of efflorescences for the control (42.2%) and for the sausages with added diphosphate (40.9%), whereas the sausages containing hexametaphosphate had significantly reduced amounts of efflorescence formation, showing only 11.9% efflorescences after 8weeks of storage. This inhibition was a result of strong complexation of hexametaphosphate with magnesium ions, thus preventing the diffusion of magnesium towards the sausage surface. This can be explained by the magnesium content on the sausage surface that increased by 163.9, 127.8, and 52.8% for the sausages without phosphate, diphosphate, and hexametaphosphate addition, respectively. The mass transport of lactate and creatine was not affected by phosphate addition. Isothermal titration calorimetry confirmed that, theoretically, 4.5g/kg of diphosphate or 2.8g/kg hexametaphosphate are required to complex 0.2g/kg magnesium ions naturally occurring in dry fermented sausages and, thus, the chosen overall phosphate concentration of 3.0g/kg was enough when adding hexametaphosphate, but not for diphosphate, to inhibit the efflorescence formation.

Characterization of Chemically and Thermally Treated Oil-in-Water Heteroaggregates and Comparison to Conventional Emulsions.

Heteroaggregated oil-in-water (O/W) emulsions formed by targeted combination of oppositely charged emulsion droplets were proposed to be used for the modulation of physical properties of food systems, ideally achieving the formation of a particulate 3-dimensional network at comparably low-fat content. In this study, rheological properties of Quillaja saponins (QS), sugar beet pectin (SBP), and whey protein isolate (WPI) stabilized conventional and heteroaggregated O/W emulsions at oil contents of 10% to 60% (w/w) were investigated. Selected systems having an oil content of 30% (w/w) and different particle sizes (d43 ≤ 1.1 or ≥16.7 µm) were additionally subjected to chemical (genipin or glutaraldehyde) and thermal treatments, aiming to increase network stability. Subsequently, their rheological properties and stability were assessed. Yield stresses (τ0 ) of both conventional and heteroaggregated O/W emulsions were found to depend on emulsifier type, oil content, and initial droplet size. For conventional emulsions, high yield stresses were only observed for SBP-based emulsions (τ0 ,SBP approximately 157 Pa). Highest yield stresses of heteroaggregates were observed when using small droplets stabilized by SBP/WPI (approximately 15.4 Pa), being higher than those of QS/WPI (approximately 1.6 Pa). Subsequent treatments led to significant alterations in rheological properties for SBP/WPI systems, with yield stresses increasing 29-fold (glutaraldehyde) and 2-fold (thermal treatment) compared to untreated heteroaggregates, thereby surpassing yield stresses of similarly treated conventional SBP emulsions. Genipin-driven treatments proved to be ineffective. Results should be of interest to food manufacturers wishing to design viscoelastic food emulsion based systems at lower oil droplet contents.

Influence of heat on miscibility of Quillaja saponins in mixtures with a co-surfactant.

Thermal treatment of mixed surfactant systems can have a major impact on their phase behavior through modified interactions between the surfactants. In this study, we investigated the miscibility behavior of aqueous binary surfactant systems composed of Quillaja saponin extract and sodium caseinate, pea protein, rapeseed lecithin, or egg lecithin at different concentration ratios (0-5% w/v) at pH3, 5, and 7 upon heat treatment (25-75°C). The results revealed that the heat-treated Quillaja saponin-sodium caseinate mixtures at pH7 remained miscible when the ratio of Quillaja saponins was equal or higher to the ratio of caseinate, otherwise the mixtures flocculated due to increased hydrophobic interactions. At pH3, the aggregation of Quillaja saponin-sodium caseinate structures was intensified by heating mainly through self-association of casein molecules. In Quillaja saponin-pea protein mixtures as well as in pure pea protein samples heating led to weakening of the gel structures at all tested pH values. In contrast, heating did not affect Quillaja saponin-rapeseed lecithin mixtures, which stayed miscible independent of pH due to electrostatic repulsive forces. Furthermore, the flocculated (pH5, 7) or aggregated (pH3) Quillaja saponin-egg lecithin mixtures were only slightly affected by heating. These results are important for understanding the interactions of binary surfactant systems when subjected to heating, which is a common processing step in many food applications.

Miscibility of Quillaja Saponins with other Co-surfactants under Different pH Values.

The miscibility behavior of mixed surfactant systems and the influence of extrinsic parameters are crucial for their application as emulsifiers. Therefore, the objective of this study was to evaluate the miscibility behavior of mixed systems composed of commercial Quillaja saponin and a co-surfactant, namely sodium caseinate, pea protein, rapeseed lecithin, or egg lecithin. These mixtures were evaluated macro- and microscopically at different concentration ratios (maximum concentration 5% w/v) at pH 3, 5, and 7 at 25 °C. The individual ingredients were also assessed for their charge properties and surface hydrophobicity. The results showed that Quillaja saponin-caseinate mixtures were miscible only at pH 7, and showed aggregation and precipitation at lower pH due to increasing electrostatic attraction forces. Rheological measurements showed that Quillaja saponin-pea protein mixtures formed gelled structures at all tested pH values mainly via association of hydrophobic patches. Quillaja saponins mixed with rapeseed lecithin were miscible at all tested pH values due to electrostatic repulsion. Quillaja saponin-egg lecithin mixtures aggregated independent of pH and concentration ratio. The microscopic analysis revealed that the lower the pH and the higher the Quillaja saponin ratio, the denser were the formed Quillaja saponin-egg lecithin aggregates. The results are summarized in ternary phase diagrams that provide a useful tool in selecting a surfactant system for food applications.