Edible Materials for Use in Dairy Product Packaging

Edibles comprise a particular subset of biobased biodegradable packaging that is constituted by both films and coatings (Petersen et al., 1999). As previously stated, edible coatings are applied and formed directly on the food product. It is possible to apply an edible coating with the required barrier properties to the food and to use, subsequently, another biobased material as primary packaging. This minimizes the amount of packaging material used. Coating of the biobased material could also be an option; the coating could, for example, be wax, which would add hydrophobicity to the packaging material (Petersen et al., 1999). For edible formulations, polysaccharides, proteins, and lipids are possible options. Additionally, an important component is the plasticizer, which enhances flexibility and extensibility. In general, these coatings exhibit higher water permeability, lower oxygen permeability, and inferior mechanical properties compared with traditional packaging (McHugh and Krochta, 1994).

Formation of coatings on food products may involve different methods such as brushing, dipping, enrobing, spraying, and electrostatic spraying (Zhong et al., 2014). Dipping is the most common laboratory scale procedure to cover the food surface. However, this technology has disadvantages such as dilution and contamination of the coating solution. Spraying is another simply and extensively used method for applying coatings. It is possible to obtain uniform coating by this technique, and it also offers the possibility of successive application without contamination of the coating solution (Andrade et al., 2012). Electrostatic spraying is an emerging technique that can be adopted to improve the traditional spraying, because this method can control the droplet size, produce homogeneous distribution, and reduce wastage (Ganesh et al., 2012).

In particular, for cheese, different studies have been performed using edible coatings for lengthening food shelf life. For example, Di Pierro et al. (2011) proposed a combined treatment to extend ricotta cheese shelf life, which comprised the use of a chitosan/ whey protein edible coating and storage under modified atmosphere (40% CO2/60% N2 mixture; plastic trays). The technique for coating forming was dipping. Microbial analysis and sensory evaluation were performed throughout 30 days of storage at 4°C. In control samples (no coating), the microbiological limit of acceptability (7 log CFU/g) was reached within 7 days for mesophilic bacteria, between days 7 and 14 for psychro- trophs, and between days 14 and 21 for lactic acid bacteria. However, the limit was never reached in the coated samples, extending the shelf life of the product packed under modified atmosphere. No difference between coated and uncoated cheese was detected in visual appearance, flavor, and odor. Additionally, coated cheese maintained its texture along the storage.

Zhong et al. (2014) compared four different coating application methods, including dipping, enrobing, spraying, and electrostatic spraying, employing three different materials (chitosan, sodium alginate, and soy protein isolate). They observed that the weight loss of coated cheese was higher than for uncoated cheese, especially for the two spraying methods, because they led to thinner and heterogeneous films. Some parts of the cheese surface were not even covered, determining a higher weight loss. As for coating materials, soy protein-coated cheese had higher weight loss compared with the other two materials, which could be explained by its lower hydrophilicity. The hardness of mozzarella cheese increased with water evaporation, and edible coatings generally delayed the hardening process and sodium alginate coatings produced the softest cheese texture, a trend that might be attributed to its higher water-retention ability. The luminosity of cheese significantly decreased during storage, but the change for sodium alginate coated cheese was smaller.

Table 3.2.3.1 shows a summary of results reported in the last years in the literature concerning edible coatings applied to cheeses. In general, researchers studied the changes of food quality (physicochemical or sensorial changes) as a consequence of the presence of the coating. Some authors evaluated the antimicrobial effectiveness of the coating tested.

The most commonly used method at the lab scale for forming edible films is the casting process. It is performed by manually spreading film solutions (matrix material, solvent, plasticizer, with or without other additives) into Petri dishes or plates, and then drying them in controlled conditions. The films formed in this way are adequate to assess their mechanical characteristics and chemical and physical properties, as well as their microbiological effectiveness and or to assay the wrapping of materials. It is usual to incorporate different additives (e.g., antimicrobials) in the film formulation. Table 3.2.3.2 summarizes recent research concerning edible films used for cheese preservation.

Table 3.2.3.1 Application of Edible Coatings to Improve the Quality of Cheese Products.

Material Used for Developing the Matrix / application procedure/ Plasticizer

Product

Effect on Product

Reference

Chitosan, agar, galactomannan (GA)/glycerol or glycerol-sorbitol (50:50)/brushing

Regional

Saloio

(semihard)

Coated cheese presented less molds at the surface than the uncoated one.

Cerqueira et al., 2009

Chitosan/glycerol/spraying with natamycin

Saloio

cheese

(semihard)

Coating inhibited development of Aspergillus niger, Penicillium crustosum, P commune, and P roqueforti in the cheese.

Fajardo el al., 2010

Galactomannan, chitosan/ glycerol or glycerol-sorbitol/ brushing

Regional

cheese

Coated cheese presented lower moisture and weight loss, smaller color change, and a decrease in growth of mesophilic bacteria and mold and yeasts during storage.

Cerqueira et al., 2010

Galactomannan/glycerol/ with nisin dipping

Ricotta

cheese

Coating slowed down the growth of L. monocytogenes during 14 days and reduced weight loss.

Martins et al., 2010

Whey protein isolate, guar gum, sunflower oil/glycerol/ natamycin, lactic acid, chitooligosaccharides/ dipping

Regional

Saloio

cheese

Coatings inhibited the growth of pathogenic or contaminant microorganisms and allowed regular growth of lactic acid bacteria throughout the storage.

Ramos et al., 2012

Coating containing natamycin and lactic acid presented the best sensory profile.

Duan et al. (2007) investigated the antimicrobial activities of chitosan-lysozyme (CL) films against tested microorganisms inoculated onto the surface of mozzarella cheese. Cheese was inoculated with Listeria monocytogenes, Escherichia coli, or Pseudomonas fluorescens at 104 CFU/g, or with mold and yeast at 102 CFU/g. Sliced cheese was subjected to covering with the films and then was individually vacuum packaged (sterile vacuum bag, FoodSaver, San Francisco, Calif., U.S.A.) and stored at 10°C. Treated cheese showed 1.25, 1.40, and 1.35 log reductions for E. coli, P fluorescens, and L. monocytogenes, respectively. Growth of molds was completely inhibited and yeast population was reduced.

Moreira et al. (2011) investigated the intrinsic antimicrobial properties of chitosan (C) when combined with sodium caseinate (SC) to prepare SC/C films. Assays were performed with SC, C, and SC/C applied as coatings or wrappers on cheese. C and SC/C applied at both immersion and as a wrapper exerted a significant bactericidal action on mesophilic, psychrotrophic, and yeasts and molds, showing in the three microbial populations a significant reduction (2.0 to 4.5 log CFU/g). An improvement of the bactericidal properties of the SC/C blend with respect to those of the C film was reported.

Fungal spoilage during refrigerated storage is one of the main safety and quality- related problems for dairy products.

Table 3.2.3.2 Application of Edible Films to Improve the Quality of Cheese Products.

Material Used for Developing the Matrix / Plasticizer

Antimicrobial in the Film

Product

Effect on Product

Reference

Sodium caseinate/ sorbitol

Mini red Babybel® (semi-soft)

Reduction in L. innocua counts in surface inoculated cheese during 1 week storage at 4°C.

Cao- Hoang et al., 2010

Casein or whey protein concentrate/ glycerol or sorbitol

potassium

sorbate

Cheddar

Cheese wrapped with edible films exhibited a lower oxidation rate than those wrapped with LDPE; showed a restriction in the growth of spoilage microorganisms.

Wagh et al., 2014

Tapioca starch/ glycerol

natamycin and nisin

Port salut

cheese

The film controlled S. cerevisiae and L. innocua growth in the surface of Port Salut cheese and acted as a barrier to post-process contamination.

Olle et al., 2014a

Tapioca starch/ glycerol

natamycin

Port salut cheese

S.cerevisiae surface growth was inhibited more efficiently with the film than with spray application of natamycin.

Olle et al., 2014b

Ture et al. (2011) studied the effect of wheat gluten (WG) and methyl cellulose (MC) biopolymers containing natamycin (NA) on the growth of Aspergillus niger and Penicillium roquefortii on the surface of fresh Kashar cheese during storage at 10°C for 30 days. Wrapping A. niger inoculated cheese with MC films containing 5-20 mg NA per 10 g resulted in approximately 2-log reductions in spore count. Two mg NA per 10 g included into WG films was sufficient to eliminate A. niger on the surface of cheese. However, MC and WG films containing NA did not cause any significant decrease in P roquefortii count on the cheese surface. Therefore, the use of WG films in dairy applications could be an effective way of controlling A. niger growth on these products.

Medeiros et al. (2014) studied the effect on the preservation of Coalho cheese of a nanolaminate coating produced by the layer-by-layer methodology using alginate and containing lysozyme. After 20 days, coated cheese showed lower values of mass loss, pH, lipidic peroxidation, and microorganisms' proliferation, and showed higher titrat- able acidity in comparison with uncoated cheese. These results suggest that gas barrier and antibacterial properties of alginate/lysozyme nanocoating can be used to extend the shelf life of Coalho cheese.

 
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