Per Væggemose Nielsen

Potential of biobased materials for food packaging

Abstract During the last decade, joint efforts by the packaging and the food industries have reduced the amount of food packaging materials. Nonetheless, used packaging materials are still very visible to the consumer in the context of disposal. Environmental issues are becoming increasingly important to the European consumer. Consequently, consumer pressure may trigger the use of biobased packaging materials as an alternative to materials produced from non-renewable resources. Biologically based packaging is defined as packaging containing raw materials originating from agricultural sources, i. e. produced from renewable, biological raw materials such as starch and bioderived monomers. These materials are not necessarily biodegradable. Consequently, this review is not limited to biodegradable packaging. To date, biodegradable packaging has commanded great attention, and numerous projects are under way in this field. One important reason for this attention is the marketing of environmentally friendly packaging materials. Furthermore, use of biodegradable packaging materials has the greatest potential in countries where landfill is the main waste management tool. Biobased packaging materials include both edible films and edible coatings along with primary and secondary packaging materials. Excellent in-depth reviews on edible films and coatings are already available 1 , 2 , 3 . Therefore, this review focuses on biobased primary packaging materials for foods. Several concerns must be addressed prior to commercial use of biobased primary food packaging materials. These concerns include degradation rates under various conditions, changes in mechanical properties during storage, potential for microbial growth, and release of harmful compounds into the packaged food product. Furthermore, the biopackaging must function as food packaging and meet the requirements of the individual food product. This review evaluates the suitability of biobased packaging for foods. Additionally, it identifies the challenges involved when using biobased packaging for different foods.

Inhibition of fungal growth on bread by volatile components from spices and herbs, and the possible application in active packaging, with special emphasis on mustard essential oil.

The effect of modified atmosphere packaging (MAP) on the most important spoilage fungi of bread was investigated. Penicillium commune, P. roqueforti, Aspergillus flavus and Endomyces fibuliger were able to grow at oxygen levels down to 0.03%, while the chalk mould E. fibuliger was capable of growing even in the presence of an oxygen absorber. High levels of carbon dioxide retarded growth but not completely. As an alternative to MAP active packaging (AP) using volatile essential oils (EO) and oleoresins (OL) from spices and herbs were tested against a range of fungi commonly found on bread. Concentrations of 1, 10 or 100 microl EO or OL were added to a filter paper placed in the lid of a Petri dish inoculated with one of the test fungi. The Petri dish was sealed hermetically to avoid the exchange of gases. Mustard essential oil showed the strongest effect. Cinnamon, garlic and clove also had high activity, while oregano oleoresin only inhibited growth weakly. Vanilla showed no inhibitory effect towards the tested microorganisms at the applied concentrations. A. flavus was more resistant than the other microorganisms while P. roqueforti was the most sensitive. Mustard essential oil was investigated in greater detail. The minimal inhibitory concentration (MIC) for the active component, allyl isothiocyanate (AITC), was determined for the same species and an additional three moulds and one yeast. MIC values ranged from 1.8 to 3.5 microg/ml gas phase. Results showed that whether AITC was fungistatic or fungicidal depended on its concentration, and the concentration of spores. When the gas phase contained at least 3.5 microg/ml, AITC was fungicidal to all tested fungi. Results of sensory evaluation showed, that hot-dog bread was more sensitive to AITC than rye bread. The minimal recognisable concentration of AITC was 2.4 microg/ml gas phase for rye bread and between 1.8 and 3.5 microg/ml gas phase for hot-dog bread. These findings showed that the required shelf-life of rye bread could be achieved by active packaging with AITC. Active packaging of hot-dog bread, may nevertheless require the additional effect of other preserving factors to avoid off-flavour formation

Physical and Mechanical Properties of Biobased Materials Starch, Polylactate and Polyhydroxybutyrate

Commercial and semi-commercial biobased materials (Polylactate, PLA, polyhydroxybutyrate, PHB, wheat starch and corn starch) were investigated. Physical and mechanical characterisation (tensile strength, elongation, tear strength, compression, gas permeability (CO 2 and O 2 ) and water vapour permeability (WVP)) was examined. Tests on both films and cups show potential use of these materials for primary food packaging, especially PLA and PHB. An interesting O 2 :CO 2 permeability ratio (1:7 to 1:12) was seen, which make these materials suitable for packaging of food with high respiration. The mechanical properties were comparable to conventional materials such as polyethylene (PE) and polystyrene (PS). The WVP measured on films ranged from 12.6 to 18.6 [g H 2 O/(m 2 x 24 h)], and on cups the range was 2.2 to 10.5 [g H 2 O x 700 μm/(m 2 x 24 h)]. The WVP for the starch-based materials seems to be the most crucial parameter, and needs improvement if these materials are to be used as food packaging.

New taxa of Neosartorya and Aspergillus in Aspergillus section Fumigati

Three new species of Neosartorya and one new Aspergillus of section Fumigati are proposed using a polyphasic approach based on morphology, extrolite production and partial β-tubulin, calmodulin, and actin gene sequences. The phylogenetic analyses using the three genes clearly show that the taxa grouped separately from the known species and confirmed the phenotypic differences. Neosartorya denticulata is characterized by its unique denticulate ascospores with a prominent equatorial furrow; N. assulata by well developed flaps on the convex surface of the ascospores which in addition have two distinct equatorial crests and N. galapagensis by a funiculose colony morphology, short and narrow conidiophores and ascospores with two wide equatorial crests with a microtuberculate convex surface. Aspergillus turcosus can be distinguished by velvety, gray turquoise colonies and short, loosely columnar conidial heads. The four new taxa also have unique extrolite profiles, which contain the mycotoxins gliotoxin and viriditoxin in N. denticulate; apolar compounds provisionally named NEPS in N. assulata and gregatins in N. galapagensis. A. turcosus produced kotanins. N.denticulata sp. nov., N. assulata sp. nov., N. galapagensis sp. nov., and A. turcosus sp. nov. are described and illustrated.

Fungicidal Effect of 15 Disinfectants against 25 Fungal Contaminants Commonly Found in Bread and Cheese Manufacturing

Resistance of 19 mold and 6 yeast species to 15 commercial disinfectants was investigated by using a suspension method in which the fungicidal effect and germination time were determined at 20 degrees C. Disinfectants containing 0.5% dodecyldiethylentriaminacetic acid, 10 g of chloramine-T per 1, 2.0% formaldehyde, 0.1% potassium hydroxide, 3.0% hydrogen peroxide, or 0.3% peracetic acid were ineffective as fungicides. The fungicidal effect of quaternary ammonium compounds and chlorine compounds showed great variability between species and among the six isolates of Penicillium roqueforti var. roqueforti tested. The isolates of P roqueforti var. carneum, P. discolor, Aspergillus versicolor, and Eurotium repens examined were resistant to different quaternary ammonium compounds. Conidia and vegetative cells were killed by alcohols, whereas ascospores were resistant. Resistance of ascospores to 70% ethanol increased with age. Both P. roqueforti var. roqueforti and E. repens showed great variability of resistance within isolates of each species.

Active Packaging of Cheese with Allyl Isothiocyanate, an Alternative to Modified Atmosphere Packaging

The natural antimicrobial compound allyl isothiocyanate (AITC), found in mustard oil, is effective against cheese-related fungi both on laboratory media and cheese. Penicillium commune, Penicillium roqueforti, and Aspergillus flavus were more sensitive to AITC when it was added just after the spores had completed 100% germination and branching had started on Czapek yeast extract agar than were spores in the dormant phase. The use of 1 AITC label (Wasaouro interior labels, LD30D, 20 by 20 mm) in combination with atmospheric air in the packaging extended the shelf life of Danish Danbo cheese from 4 1/2 to 13 weeks. Two AITC labels extended the shelf life from 4 1/2 to 28 weeks. Both 1 and 2 labels in combination with modified atmosphere packaging extended the shelf life of the cheese from 18 to 28 weeks. This study showed that AITC was absorbed in the cheese, but it was not possible to detect any volatile breakdown products from AITC in the cheese. Cheese stored for up to 12 weeks with an AITC label had an unacceptable mustard flavor. The mustard flavor decreased to an acceptable level between weeks 12 and 28. Cheese stored in atmospheric air had a fresher taste without a CO2 off-flavor than did cheese stored in modified atmosphere packaging. AITC may be a good alternative to modified atmosphere packaging for cheese. The extended shelf life of cheese in the package is very desirable: the cheese can be transported longer distances, and the packaging can be used for the final maturing of the cheese. Furthermore, AITC can address problems such as pinholes and leaking seals in cheese packaging.

Proteome analysis of Aspergillus niger: lactate added in starch-containing medium can increase production of the mycotoxin fumonisin B2 by modifying acetyl-CoA metabolism.

BackgroundAspergillus niger is a filamentous fungus found in the environment, on foods and feeds and is used as host for production of organic acids, enzymes and proteins. The mycotoxin fumonisin B2 was recently found to be produced by A. niger and hence very little is known about production and regulation of this metabolite. Proteome analysis was used with the purpose to reveal how fumonisin B2 production by A. niger is influenced by starch and lactate in the medium.ResultsFumonisin B2 production by A. niger was significantly increased when lactate and starch were combined in the medium. Production of a few other A. niger secondary metabolites was affected similarly by lactate and starch (fumonisin B4, orlandin, desmethylkotanin and pyranonigrin A), while production of others was not (ochratoxin A, ochratoxin alpha, malformin A, malformin C, kotanin, aurasperone B and tensidol B). The proteome of A. niger was clearly different during growth on media containing 3% starch, 3% starch + 3% lactate or 3% lactate. The identity of 59 spots was obtained, mainly those showing higher or lower expression levels on medium with starch and lactate. Many of them were enzymes in primary metabolism and other processes that affect the intracellular level of acetyl-CoA or NADPH. This included enzymes in the pentose phosphate pathway, pyruvate metabolism, the tricarboxylic acid cycle, ammonium assimilation, fatty acid biosynthesis and oxidative stress protection.ConclusionsLactate added in a medium containing nitrate and starch can increase fumonisin B2 production by A. niger as well as production of some other secondary metabolites. Changes in the balance of intracellular metabolites towards a higher level of carbon passing through acetyl-CoA and a high capacity to regenerate NADPH during growth on medium with starch and lactate were found to be the likely cause of this effect. The results lead to the hypothesis that fumonisin production by A. niger is regulated by acetyl-CoA.

Protection by fungal starters against growth and secondary metabolite production of fungal spoilers of cheese

The influence of fungal starter cultures on growth and secondary metabolite production of fungal contaminants associated with cheese was studied on laboratory media and Camembert cheese. Isolates of the species Penicillium nalgiovense, P. camemberti, P. roqueforti and Geotrichum candidum were used as fungal starters. The species P. commune, P. caseifulvum, P. verrucosum, P. discolor, P. solitum, P. coprophilum and Aspergillus versicolor were selected as contaminants. The fungal starters showed different competitive ability on laboratory media and Camembert cheese. The presence of the Penicillium species, especially P. nalgiovense, showed an inhibitory effect on the growth of the fungal contaminants on laboratory media. G. candidum caused a significant inhibition of the fungal contaminants on Camembert cheese. The results indicate that G. candidum plays an important role in competition with undesirable microorganisms in mould fermented cheeses. Among the starters, P. nalgiovense caused the largest reduction in secondary metabolite production of the fungal contaminants on the laboratory medium. On Camembert cheese no significant changes in metabolite production of the fungal contaminants was observed in the presence of the starters.

Effect of modified atmosphere packaging and water activity on growth of Eurotium amstelodami, E. chevalieri and E. herbariorum on a sponge cake analogue

The combined effects of water activity (aw), oxygen (O2) and carbon dioxide (CO2) levels on growth variables of three species of Eurotium (two isolates of each) on a sponge cake analogue were studied. The use of a multivariate statistical method (PLS) for the analysis of data showed that in general, the fungi had the same behaviour, according to their growth responses, to changes in the three tested factors. However, the maximal growth of E. herbariorum was somewhat more affected by the O2 level at lower CO2 levels. On the other hand, CO2, aw and the interaction between CO2 and O2 were found to be the most significant factors describing growth variables. In addition, the model found in this study had a good predictive power. There was a positive correlation between the CO2 concentration in the bags and the lag phase, and a negative correlation between the growth rate and maximum mycelial growth. In general, no isolates were able to growth when CO2 concentrations were higher than 60% under anaerobic conditions. At lower values of CO2, aw and O2 influenced growth variables. Low levels of O2 (0·02–0·5%) did not affect the growth variables studied when levels of CO2 in the bags were high. However, when the CO2 concentration decreased, the different O2 levels had an influence on the growth variables, i.e., a small difference in the concentration of O2 can allow fungi to grow.

Ecophysiological characterization of common food-borne fungi in relation to pH and water activity under various atmospheric compositions

The combined effects of pH, water activity (aw), oxygen (O2) and carbon dioxide (CO2) levels on growth and sporulation of 10common food‐borne fungi were studied. The use of a multivariate statistical method (PLS) for the analysis of data showed that the fungi could be grouped according to their physiological response to changes in the four tested factors. Carbon dioxide, aw and pH were found to be the most significant factors describing differences and similarities among the fungi. Maximal inhibitory effect of elevated levels of CO2 (5–25%) and decreased aw (0·99–0·95) varied among the 10 species from 6 to 77% and from 52 to 100%, respectively. Sporulation of the fungi was sensitive to all tested factors. Furthermore, interaction of CO2 and aw displayed a significant effect on sporulation. It was shown that different fungal species associated with the same ecosystem responded similarly to changes in the tested factors. Thus, fungi which are not phylogenetically related may be physiologically related or show a common strategy of life.