Raija Lantto

Crosslinking Food Proteins for Improved Functionality

Different possibilities for protein crosslinking are examined in this review, with special emphasis on enzymatic crosslinking and its impact on food structure. Among potential enzymes for protein crosslinking are transglutaminase (TG) and various oxidative enzymes. Crosslinking enzymes can be applied in cereal, dairy, meat, and fish processing to improve the texture of the product. Most of the current commercial applications are based on TG. The reaction mechanisms of the crosslinking enzymes differ, which in turn results in different technological properties.

Effects of Laccase-Mediator Combinations on Wool

The effects of Myceliophthora thermophila laccase are studied alone and in combina tion with the mediators violuric acid (VA) or l-hydroxybenzotriazole (HBT) on wool fibers, cystine, and tyrosine. Without a mediator, laccase is unable to oxidize wool or the amino acids. In the presence of either VA or HBT, oxygen consumption is observed, indicating oxidation of the secondary substrates of the laccase, i.e., wool, cystine, or tyrosine. The oxidation levels are low. Laccase/HBT reacts more efficiently with wool and tyrosine and laccase/VA with cystine. With the chosen enzyme dosage and mediator concentration, about 2-4% of cystine and about 1 % of tyrosine are oxidized. The slight oxidation of wool fibers is not sufficient to affect the surface chemistry or alkaline solubility of the fibers, although staining of the fibers by the oxidized mediators is significant.

The impact of fermentation with exopolysaccharide producing lactic acid bacteria on rheological, chemical and sensory properties of pureed carrots (Daucus carota L.)

Fermentation with lactic acid bacteria (LAB) offers a natural means to modify technological and nutritional properties of foods and food ingredients. This study explored the impact of fermentation with different exopolysaccharide (EPS) producing LAB on rheological, chemical and sensory properties of puréed carrots in water, as a vegetable model, with the focus on texture formation. The screening of 37 LAB strains for starter selection revealed 16 Lactobacillus, Leuconostoc and Weissella strains capable of EPS (dextran, levan, and/or β-glucan) production in the carrot raw material. Fermentations with five out of six selected EPS producers modified perceived texture of the liquid carrot model (p<0.05). The formation of low-branched dextran correlated with perceived thickness, whereas the production of β-glucan correlated with perceived elasticity. Low-branched dextran producing Weissella confusa and Leuconostoc lactis strains produced thick texture accompanied by pleasant odour and flavour. The fermentation with the selected EPS-producing LAB strains is a promising clean label approach to replace hydrocolloid additives as texturizers in vegetable containing products, not only carrot.

Using crosslinking enzymes to improve textural and other properties of food

Publisher Summary This chapter explains that food texture plays a major role in food product quality. The rheological properties of a food are determined by the number of weak and strong physical interactions and the permanent covalent bonds, crosslinks, present in the food matrix. Covalent crosslinks make the major contribution to the firmness of food matrices. Crosslinks can be introduced to a food matrix by chemical, enzymatic, and physical means as reviewed by Munindar P. Singh (1991) and Scott N. Gerrard (2002) . Enzymatic crosslinking of food biopolymers is an attractive option owing to the specificity of enzymes and mild reaction conditions. Both food proteins and carbohydrates can be crosslinked by enzymes. Sensory perception of texture plays an important role in different types of foods. The significance of food texture has further been increased with the trend toward low fat products and “natural” additive-free products. Enzymes provide specific and natural means for tailoring food structure. By the use of enzymes, it will be possible to transform inherently available food components into functional ingredients during food processing and manufacturing. Enzymatic crosslinking in the food matrix can occur via proteins or certain carbohydrates. The type of enzyme used affects the chemistry of the crosslink formed and subsequently the structure of the biopolymer network of the food product.

Effect of Enzyme-Aided Cell Wall Disintegration on Protein Extractability from Intact and Dehulled Rapeseed (Brassica rapa L. and Brassica napus L.) Press Cakes

Cell-wall- and pectin-degrading enzyme preparations were used to enhance extractability of proteins from rapeseed press cake. Rapeseed press cakes from cold pressing of intact Brassica rapa and partially dehulled Brassica napus seeds, containing 36-40% protein and 35% carbohydrates, were treated with pectinolytic (Pectinex Ultra SP-L), xylanolytic (Depol 740L), and cellulolytic (Celluclast 1.5L) enzyme preparations. Pectinex caused effective disintegration of embryonic cell walls through hydrolysis of pectic polysaccharides and glucans and increased protein extraction by up to 1.7-fold in comparison to treatment without enzyme addition. Accordingly, 56% and 74% of the total protein in the intact and dehulled press cakes was extracted. Light microscopy of the press cakes suggested the presence of pectins colocalized with proteins inside the embryo cells. Hydrolysis of these intracellular pectins and deconstruction of embryonic cell walls during Pectinex treatment were concluded to relate with enhanced protein release.

Directing enzymatic cross-linking activity to the air–water interface by a fusion protein approach

Enzymatic cross-linking of proteins is of great interest due to an effective and controlled way of modifying the structures of protein networks. Enzyme-aided structural engineering aims at enhanced stabilisation of foams, emulsions and dispersions by enzymatically inducing intra- and intermolecular cross-links between proteins in continuous phase and/or at interfaces. Formation of stronger interfacial structures protects air bubbles or oil droplets against coalescence, and in some applications, may even be preferable to bulk reactions. In this work we studied direction of enzymatic cross-linking reactions to the air–water interface by enhancing the functionality of enzymes as fusion proteins. We used a hydrophobin–laccase fusion protein, HFBI–MaL, where the surface active hydrophobin component facilitates the access for laccase to cross-link β-casein film directly at the air–water interface. As a result, enhanced cross-linking was shown by means of surface dilatational rheology, where increased G moduli indicated formation of a stronger film with the fusion protein compared to native laccase.

Impact of Total Solid Content and Extraction pH on Enzyme-Aided Recovery of Protein from Defatted Rapeseed (Brassica rapa L.) Press Cake and Physicochemical Properties of the Protein Fractions

Pectinase treatment was used to facilitate protein recovery from defatted rapeseed (Brassica rapa) cold-pressing residue in water-lean conditions and without pH adjustment. Effect of extraction pH on protein yield and physiochemical properties of the protein concentrates was assessed. Enzymatic hydrolysis of carbohydrates was feasible at high (40%) solid content and improved protein recovery at pH 6. Comparable protein yields (40-41% of total protein) from enzyme-aided water extraction (pH 6) and nonenzymatic alkaline extraction (pH10) at 10% solid content suggested that after enzymatic treatment, rapeseed protein could be extracted without exposure to alkali. However, water extraction required dilute conditions, whereas alkaline extraction was feasible also at 20% solid content. The water extracts possessed better protein solubility, higher ζ-potential, and smaller particle size than isoelectric precipitates from alkaline extraction, indicating higher dispersion stability. This is suggested to be mediated by electrostatic interactions between proteins and pectic carbohydrates in the water extracts.

Biocompounds from rapeseed oil industry co-stream as active ingredients for skin care applications

Despite the great number of substances produced by the skincare industry, very few of them seem to truly have an effect on the skin. Therefore, given the social implications surrounding physical appearance, the search for new bioactive compounds to prevent or attenuate skin ageing and enhance self‐image is a priority of current research. In this context, being rich in valuable compounds, such as proteins, phenolics, lipids and vitamins, this study is focused on the potential activity of rapeseed press cake hydrolysates to be used as raw materials for skincare applications.