Relevance of nanocomposite packaging on the stability of vacuum-packed dry cured ham.

In this study effects of a novel high barrier multilayer polyamide film containing dispersed nanoclays (PAN) on the stability of vacuum packed dry-cured ham were investigated during 90days refrigerated storage in comparison with non-modified multilayer polyamide (PA) and a commercial high barrier film. Characteristic bands of the mineral in FT-IR spectra confirmed the presence of nanoclays in PAN, enhancing oxygen transmission barrier properties and UV protection. Packaging in PAN films did not originate significant changes on colour or lipid oxidation during prolonged storage of vacuum-packed dry-cured ham. Larger oxygen transmission rates in PA films caused changes in CIE b* during refrigerated storage. Ham quality was not affected by light exposition during 90days and only curing had a significant benefit on colour and TBARS, being cured samples more stable during storage in all the packages used. Packaging of dry-cured ham in PAN was equivalent to commercial high barrier films.

Cyto-genotoxic and oxidative effects of a continuous UV-C treatment of liquid egg products.

UV-C treatment of food is a promising non-thermal processing technology to improve food safety and preservation. Most of the chemical constituents of food absorb UV-C light that can lead to chemical modifications and quality changes. This work investigated the effects of UV-C treatment of liquid egg products on lipid, protein oxidations and potential cyto- and genotoxic effects on intestinal epithelial cells in vitro. Egg preparations (egg white, yolk, liquid whole egg) were treated with UV-C (254 nm, volumetric doses between 0 and 115,619 J L(-1)) using a commercial UV-C processing unit equipped with a Dean Flow reactor. UV-C treatment at high doses (from 32,181 J L(-1), about 2 times higher than that needed to inactivate 5 log of relevant microorganisms) showed an increased lipid oxidation in egg yolk and slight effects in liquid whole eggs; this was confirmed by slightly but not statistically significant increased peroxide values. UV-C induced also slight protein damage, characterised by the total sulfhydryl group reduction. These UV-C-induced oxidative modifications in egg preparations however did not cause any increase in the cyto- or genotoxic (DNA strand breaks) effects in intestinal Caco-2 cells.

Study of the antifungal potential of novel cellulose/copper composites as absorbent materials for fruit juices.

Cellulose/copper composites with antifungal properties have been synthesized by physical/chemical methods. Physical treatments by heat or by a combination of heat and UV radiation provided composites with metallic copper and excellent interfacial adhesion; in contrast, chemical reduction with borohydride generated small although partially aggregated copper oxide nanoparticles. Copper micro/nano-particles and copper ions (Cu(2+)) were released from the cellulose matrix at an adequate rate to achieve a strong antimicrobial activity against Saccharomyces cerevisiae in in vitro experiments. Moreover, the copper oxide composites showed an excellent antifungal activity in pineapple and melon juice, reducing about 4 log cycles the loads of spoilage-related yeasts and moulds. The metallic copper composites reduced in 4 log cycles the load of yeasts and moulds in pineapple juice, although their antifungal activity was weaker in contact with melon juice. Copper loaded absorbent materials could be selectively implemented during the shelf-life of minimally processed fruits to reduce the number of spoilage-related microorganisms in the drip.

Characterization of phenolic content, in vitro biological activity, and pesticide loads of extracts from white grape skins from organic and conventional cultivars.

Grape skin extracts of Riesling Vitis vinifera L. grapes from conventionally or organically managed cultivars were compared on the basis of their phenolic content, antioxidant capacity, antimicrobial and antimutagenic properties and pesticide loads. Promising results on their biological properties suggest that those extracts would be valuable as food preservatives. The antioxidant capacity of conventional extracts was significantly higher, according to the higher content in catechin, epicatechin and procyanidin B. Pesticide loads did not affect the antimutagenic or antimicrobial properties of the extracts. Both extracts inhibited the growth of Gram-positive foodborne pathogens such as Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium to similar extents. Possibly as a result of higher amounts of quercetin and its derivatives, higher antimicrobial effects against Listeria monocytogenes and Salmonella typhimurium were observed for the organic white grape skin extracts. Conventional or organic extracts did not show remarkable antimutagenic effects when tested against the mutagen IQ by means of the Ames test. Due to the presence of fungicides, the conidial germination of Penicillium expansum, Penicillium chrysogenum and Aspergillus niger, were inhibited by 95% by conventional GSE, while negligible effects were observed with organic grape extracts. The latter, however, showed inhibitory effects against Trichoderma viridie and Aspergillus versicolor.

Cellulose-silver nanoparticle hybrid materials to control spoilage-related microflora in absorbent pads located in trays of fresh-cut melon.

The antimicrobial activity of newly developed cellulose-silver nanoparticle hybrid materials was investigated during storage of minimally processed "Piel de Sapo" melon. Silver nanoparticles were produced after in-situ reduction by physical methods of 1% silver nitrate adsorbed on cellulose fibres; they accounted between 5 and 35 nm diameter, and were not aggregated. Fresh-cut melon pieces were stored for 10 days at 4 degrees C under natural modified atmosphere packaging, in presence or absence of silver loaded absorbent pads. The evolution of headspace gas composition, quality parameters, and the antimicrobial activity against spoilage-related microorganisms were investigated. The cellulose-silver nanoparticle hybrid materials released silver ions after melon juice impregnated the pad. The released silver ions were particularly useful to control the population of spoilage-related microorganisms in cellulose based absorbent pads in contact with vegetable matrices, showing a low chelating effect against silver ions; the lag phases of the microorganisms were considerably incremented and microbial loads in the pads remained in average approx. 3 log(10) CFU/g below the control during the investigated storage period. Furthermore, the presence of silver loaded absorbent pads retarded the senescence of the melon cuts, presenting remarkably lower yeast counts, lower degrees Brix values, and a juicier appearance after 10 days of storage.

Migration of antimicrobial silver from composites of polylactide with silver zeolites.

UNLABELLED: Silver ion migration and antimicrobial activity of PLA (polylactic acid-polylactide)/silver zeolite composites were investigated. Films prepared by solution-casting/solvent evaporation, or by melt-mixing/compression molding were compared. Silver migration to food simulants and TSB (tryptone soy broth) was quantified at different temperatures. Antimicrobial activity against Staphylococcus aureus and Escherichia coli was measured following the Japanese Industrial Standard JIS Z 2801. All types of PLA/silver zeolite composites released Ag(+) ions. A more intense ionic exchange with the zeolites and a significant, but low, antimicrobial activity in solution were found in cast films. To attain antimicrobial effects, however, migrated ions ought to be in the range of the legal limit of 0.05 mg Ag(+)/kg food stated by the European Food Safety Agency (EFSA). Silver migration and antimicrobial activity were sensitive to the methodology chosen to process the PLA films, the ionic strength of the medium, and the ion motility in the polymer matrix. PRACTICAL APPLICATION: Silver exchanged zeolites incorporated in food contact polymers are gaining importance as antimicrobial agents. Migration of silver ions from polymer matrices, however, is legally restricted. Therefore a compromise between silver migration and antimicrobial activity needs to be critically analyzed to validate novel materials in food packaging applications.

Reduction of the spoilage-related microflora in absorbent pads by silver nanotechnology during modified atmosphere packaging of beef meat.

Silver-based antibacterial hybrid materials have been developed by in situ reduction of silver nitrate (1%) adsorbed on cellulose fibers by thermal and UV treatments. Microscopy revealed that the silver nanoparticles were dispersed and regular in shape. Migrated silver ions achieved 60 ppm in beef meat exudates. The ability of the silver-loaded absorbent pads to lower microbial contamination of exuded fluids was studied during storage of beef meat in modified atmosphere packaging. Cellulose-silver hybrid materials reduced the levels of the major microbial groups (total aerobic bacteria, lactic acid bacteria, Pseudomonas spp., and Enterobacteriaceae) present in the absorbent pads by an average of 1 log CFU/g during the entire storage period. The levels of total aerobic bacteria and Pseudomonas spp. were significantly reduced in the presence of silver ions, whereas lactic acid bacteria were less sensitive and not significantly affected. Enterobacteriaceae levels remained under the detection limit when silver was present. Neither the color of the meat nor the microbial loads were markedly affected by the presence of the silver-based antimicrobial hybrid materials.