Marilena Esposito

Enzymatic milk clotting activity in artichoke (Cynara scolymus) leaves and alpine thistle (Carduus defloratus) flowers. Immobilization of alpine thistle aspartic protease.

Two different milk clotting enzymes, belonging to the aspartic protease family, were extracted from both artichoke leaves and alpine thistle flowers, and the latter was covalently immobilized by using a polyacrylic support containing polar epoxy groups. Our findings showed that the alpine thistle aspartic protease was successfully immobilized at pH 7.0 on Immobeads IB-150P beads and that, under these experimental conditions, an immobilization yield of about 68% and a recovery of about 54% were obtained. Since the enzyme showed an optimal pH of 5.0, a value very similar to the one generally used for milk clotting during cheese making, and exhibited a satisfactory stability over time, the use of such immobilized vegetable rennet for the production of novel dairy products is suggested.

Plasticizing Effects of Polyamines in Protein-Based Films

Zeta potential and nanoparticle size were determined on film forming solutions of native and heat-denatured proteins of bitter vetch as a function of pH and of different concentrations of the polyamines spermidine and spermine, both in the absence and presence of the plasticizer glycerol. Our results showed that both polyamines decreased the negative zeta potential of all samples under pH 8.0 as a consequence of their ionic interaction with proteins. At the same time, they enhanced the dimension of nanoparticles under pH 8.0 as a result of macromolecular aggregations. By using native protein solutions, handleable films were obtained only from samples containing either a minimum of 33 mM glycerol or 4 mM spermidine, or both compounds together at lower glycerol concentrations. However, 2 mM spermidine was sufficient to obtain handleable film by using heat-treated samples without glycerol. Conversely, brittle materials were obtained by spermine alone, thus indicating that only spermidine was able to act as an ionic plasticizer. Lastly, both polyamines, mainly spermine, were found able to act as “glycerol-like” plasticizers at concentrations higher than 5 mM under experimental conditions at which their amino groups are undissociated. Our findings open new perspectives in obtaining protein-based films by using aliphatic polycations as components.

Transglutaminase Cross-Linked Edible Films and Coatings for Food Applications

Abstract Transglutaminases are cross-linking enzymes available for catalyzing covalent isopeptide bond formation among protein molecules of different origins. These enzymes, mainly the microbial molecular form, are considered a possible tool to improve physicochemical properties such as solubility, water binding or emulsifying capacity, foaming, viscosity, elasticity, and gelation of proteins intended for human consumption. In recent years, different biotechnological applications of transglutaminases have also come to light in areas ranging from material sciences to medicine. In this chapter, we review the most important applications of such biocatalysts in the preparation of different innovative biodegradable materials that are potentially useful as edible films and food coatings.

Dairy Whey Protein-Based Edible Films and Coatings for Food Preservation

Abstract Edible films are increasingly used to coat perishable foodstuff to protect their nutritional and organoleptic properties. Several byproducts of goods and processes, such as dairy whey (DW) proteins, may be sustainable feedstocks to produce edible films. Our studies demonstrated that DW protein-based edible coatings (1) reduce growth of microbial contaminants, extending the shelf life of fresh cheese packed under modified atmosphere; (2) decrease moisture loss in both doughnuts and french fries when applied before food frying with a consequent significant decrease of oil content in the coated fried foods; (3) hinder moisture absorption by biscuits during a long storage period, preventing the food matrix conversion from a glassy state to a rubbery state; and (4) avoid fresh-cut apple, potato, and carrot spoilage during storage without any change in fruit and vegetable hardness and chewiness.