Physicochemical and antimicrobial characterization of beeswax–starch food-grade nanoemulsions incorporating natural antimicrobials

Nanoemulsions are feasible delivery systems of lipophilic compounds, showing potential as edible coatings with enhanced functional properties. The aim of this work was to study the effect of emulsifier type (stearic acid (SA), Tween 80 (T80) or Tween 80/Span 60 (T80/S60)) and emulsification process (homogenization, ultrasound or microfluidization) on nanoemulsion formation based on oxidized corn starch, beeswax (BW) and natural antimicrobials (lauric arginate and natamycin). The response variables were physicochemical properties, rheological behavior, wettability and antimicrobial activity of BW–starch nanoemulsions (BW–SN). The BW–SN emulsified using T80 and microfluidized showed the lowest droplet size (77.6 ± 6.2 nm), a polydispersion index of 0.4 ± 0.0 and whiteness index (WI) of 31.8 ± 0.8. This BW–SN exhibited a more negative ζ-potential: −36 ± 4 mV, and Newtonian flow behavior, indicating great stability. BW–SN antimicrobial activity was not affected by microfluidization nor the presence of T80, showing inhibition of the deteriorative fungi R. stolonifer, C. gloeosporioides and B. cinerea, and the pathogenic bacterium S. Saintpaul. In addition, regardless of emulsifier type and emulsification process, BW–SN applied on the tomato surface exhibited low contact angles (38.5° to 48.6°), resulting in efficient wettability (−7.0 mN/m to −8.9 mN/m). These nanoemulsions may be useful to produce edible coatings to preserve fresh-produce quality and safety.We are grateful to CONACyT for PhD grant to Teresita Arredondo Ochoa, and financial support for project No. 166751. Special thanks are given to Alfonso Pérez for help on DSC analysis and Ma. Lourdes Palma Tirado for technical support on micrographs

DEVELOPMENT OF ENZIMATICALLY RETICULATED EDIBLE FILMS TO BE USED AS ACTIVE PACKAGING

The use of plastic packaging is widely diffuse because this material possesses several advantages such as being lightweight, durable, easy to carry and having a low cost production. However, plastic packagings have the problem of not being biodegradable and, therefore, have a global environmental impact. Moreover when in contact with foods, petrol-derived plastics can be harmful for human health especially if the convey plasticizers such as polyvinylclhoride (PVC) that is can cause severe damages to endocrin system. A solution to this problem is to direct attention towards the development of packaging designed primarily for the food industry. (Floros et al.,1997). These innovative materials, that could be named edible films, are obtained from natural molecules like proteins, polysaccharides or lipids and are prepared using different techniques such as spray-drying, casting and dip-coating. In some cases, these films can be used as carriers of antimicrobial agents and are defined as active packaging. However, even if edible films are harmless for both human and environment health,, they possess pour mechanical and barriers properties compared to the traditional ones. Such properties can be improved by the inclusion of covalent bonds by transglutaminase (TGase), that is a biotechnological tool that can polymerize proteins through intermolecular cross-links -( - glutamyl) lysine. In this work we have obtained edible films made of Citrus pectin and TGase-crosslinked whey proteins, and evaluated their use as active packaging when conveying a peptide with antimicrobial activity. Moreover such films have been used to coat dry biscuits and fryed donuts to establish their effectiveness in extending biscuit shelf-life and reduction of fat up-take in donuts. The milk whey is the residue of cheese, is a highly polluting waste material despite being a reserve of high biological value food. As source of such proteins we have used a purchased product named Whey Protein Isolate (WPI) contaning: β-lactoglobulin (65%), α-lactoalbumin (25%), and bovine serum albumin (8%). WPI is largely used in the food industry as a milk substitute, for the production of ice cream, for increasing the protein content of foods, and as food for people that practise hard physical activity. Pectin is a heteropolysaccharide, consists mainly of acid D-galacturonic molecules linked by (-(1-4) and is obtained mainly from the peel of fruits of the Citrus family. In isolated form, pectin is rapidly reassociated to form aggregates or networks may also interact with proteins through hydrogen-type bonds, and ionic bonds.(Liu and Kost, 2009). These interactions can be improved by several treatments to obtain three dimensional complexes with improved mechanical and barrier properties. At the first beginning, the present research was focused on indentifying the best WPI/Pectin ratio and the pHc in order to obtaining the maximum degree of complexation. These parameters allowed us to obtain a stable colloidal solution that was used as the basis for the production of edible films crosslinked or not by TGase. Results have shown that the films obtained at a 4:1 ratio WPI/Pectin and pH 5.1 (pHc) crosslinked with TGase showed good mechanical properties and barrier water vapor and oxygen. In addition, the crosslinking created by TGase makes them a valid support for the release of molecules with antimicrobial activity. The application of these films by dip-coating technique has allowed us to create a layer on surface foods such as dry biscuits and donuts. Results obtained have shown that the application of the films on dry biscuits decreases absorption of water prolonging the shell-life, while applying the same coating to fried products like donuts significantly reduces the oil absorption. In conclusion, the TGase turns out to be a valuable biotechnology tool to reticulate soluble complexes obtained from WPI and Pectin, that allow to obtain edible films with good mechanical and barrier properties useful for valuable applications in the food field

Multilayered Edible Coatings to Enhance Some Quality Attributes of Ready-to-Eat Cherimoya (<i>Annona cherimola</i>)

Multilayer coating can be applied on fresh fruit to protect and enhance its shelf life. This study evaluated the application of a multilayer protein and chitosan coating on fresh cherimoya. To determinate the effect of the multilayer coating on the shelf life on the fruit, total phenolic content, pH, °Brix, weight loss, and hardness values were tested. The ripening process is associated with an increase of soluble solids, and results showed that the presence of the multilayered coating maintains the total phenolic content, pH, and °Brix values over time while reducing the water loss. This effect is probably due to the presence of the coating that creates a barrier on the food surface that reduces the respiration rate and affects the ripening process, demonstrating the method’s feasibility to be used to enhance the shelf life of fresh-cut cherimoya

Edible Coating from Enzymatically Reticulated Whey Protein-Pectin to Improve Shelf Life of Roasted Peanuts

Edible coatings are a viable alternative method to enhance food shelf life that can be designed using different biopolymers. This study evaluated the effect of a whey protein–pectin coating reticulated by microbial transglutaminase (mTG) on improving roasted peanuts’ shelf life. Peroxide value, water content, peanut color, and the solution’s contact angle were studied. The latter was improved by the presence of the enzyme. The results showed that the presence of the coating on the peanut surface reduces the peroxide value and water content, probably as a consequence of an improved barrier effect due to the presence of mTG, which protects the kernel. Enzymatically reticulated whey protein–pectin coatings are a promising alternative to enhance the shelf life of roasted peanut kernels using natural ingredients

Application of transglutaminase crosslinked whey protein-pectin coating improves egg quality and minimizes the breakage and porosity of eggshells

It is well known that an effective way to improve the quality attributes of food is the use of coatings. Moreover, there is evidence of the use of dairy byproducts to design coatings to improve the shelf life of food products. This study was conducted to explore the effectiveness of a film forming solution containing whey protein&#8315;pectin complex enzymatically reticulated by transglutaminase (TGase) applied as a coating on eggshells to preserve the internal quality of eggs stored under environmental conditions (25 &#177; 1 &#176;C and 35% HR) during 15 days storage. Eggs properties tested included yolk index, albumen and yolk pH, albumen CO2 content, water loss, shell strength, and microbial permeability through the shell. The results showed that the coating maintained a higher yolk index and albumen carbon dioxide content, reduced the weight loss and increased both albumen and yolk pH values with respect to the uncoated eggs. All coated eggshells showed greater strength than those of uncoated eggs. Moreover, by using Blue Lake dye penetration method we demonstrated that the coating reduced the Blue Lake dye penetration confirming the effectiveness of the coating on the reduction of post-wash bacterial penetration. These results suggest that the studied coating can be useful to preserve internal egg quality but also to reduce the breakage of eggshell and egg microbial contamination. Based on this result we can conclude that the coating made with whey protein&#8315;pectin crosslinked by TGase could be an effective strategy to increase the shelf life of eggs preserved in environmental conditions and to reduce economic losses due to the eggs breakage during their marketing

Modified Starch-Chitosan Edible Films: Physicochemical and Mechanical Characterization

Starch and chitosan are widely used for preparation of edible films that are of great interest in food preservation. This work was aimed to analyze the relationship between structural and physical properties of edible films based on a mixture of chitosan and modified starches. In addition, films were tested for antimicrobial activity against Listeria innocua. Films were prepared by the casting method using chitosan (CT), waxy (WS), oxidized (OS) and acetylated (AS) corn starches and their mixtures. The CT-starches films showed improved barrier and mechanical properties as compared with those made from individual components, CT-OS film presented the lowest thickness (74 ± 7 µm), water content (11.53% ± 0.85%, w/w), solubility (26.77% ± 1.40%, w/v) and water vapor permeability ((1.18 ± 0.48) × 10−9 g·s−1·m−1·Pa−1). This film showed low hardness (2.30 ± 0.19 MPa), low surface roughness (Rq = 3.20 ± 0.41 nm) and was the most elastic (Young’s modulus = 0.11 ± 0.06 GPa). In addition, films made from CT-starches mixtures reduced CT antimicrobial activity against L. innocua, depending on the type of modified starch. This was attributed to interactions between acetyl groups of AS with the carbonyl and amino groups of CT, leaving CT with less positive charge. Interaction of the pyranose ring of OS with CT led to increased OH groups that upon interaction with amino groups, decreased the positive charge of CT, and this effect is responsible for the reduced antimicrobial activity. It was found that the type of starch modification influenced interactions with chitosan, leading to different films properties

Modified Starch-Chitosan Edible Films: Physicochemical and Mechanical Characterization

Starch and chitosan are widely used for preparation of edible films that are of great interest in food preservation. This work was aimed to analyze the relationship between structural and physical properties of edible films based on a mixture of chitosan and modified starches. In addition, films were tested for antimicrobial activity against Listeria innocua. Films were prepared by the casting method using chitosan (CT), waxy (WS), oxidized (OS) and acetylated (AS) corn starches and their mixtures. The CT-starches films showed improved barrier and mechanical properties as compared with those made from individual components, CT-OS film presented the lowest thickness (74 ± 7 µm), water content (11.53% ± 0.85%, w/w), solubility (26.77% ± 1.40%, w/v) and water vapor permeability ((1.18 ± 0.48) × 10−9 g·s−1·m−1·Pa−1). This film showed low hardness (2.30 ± 0.19 MPa), low surface roughness (Rq = 3.20 ± 0.41 nm) and was the most elastic (Young’s modulus = 0.11 ± 0.06 GPa). In addition, films made from CT-starches mixtures reduced CT antimicrobial activity against L. innocua, depending on the type of modified starch. This was attributed to interactions between acetyl groups of AS with the carbonyl and amino groups of CT, leaving CT with less positive charge. Interaction of the pyranose ring of OS with CT led to increased OH groups that upon interaction with amino groups, decreased the positive charge of CT, and this effect is responsible for the reduced antimicrobial activity. It was found that the type of starch modification influenced interactions with chitosan, leading to different films properties

Landscape genetics, adaptive diversity, and population structure in P. vulgaris

Key words: domestication, genetic diversity, landraces, landscape genetics, Phaseolus vulgaris, SNP genotyping, wild accessions. Summary Here we studied the organization of genetic variation of the common bean (Phaseolus vulgaris) in its centres of domestication. We used 131 single nucleotide polymorphisms to investigate 417 wild common bean acces-sions and a representative sample of 160 domesticated genotypes, including Mesoamerican and Andean genotypes, for a total of 577 accessions. By analysing the genetic spatial patterns of the wild common bean, we documented the existence of several genetic groups and the occurrence of variable degrees of diversity in Mesoamerica and the Andes. Moreover, using a landscape genetics approach, we demon-strated that both demographic processes and selection for adaptation were responsible for the observed genetic structure. We showed that the study of correlations between markers and ecological variables at a continental scale can help in identifying local adaptation genes. We also located putative areas of common bean domestication in Mesoamerica, in the Oaxaca Valley, and the Andes, in southern Bolivia-northern Argentina. These observations are of paramount importance for the conservation and exploitation of the genetic diversity preserved within this species and other plant genetic resources