Tim Nielsen

Antioxidant ability of BHT‐ and α‐tocopherol‐impregnated LDPE film in packaging of oatmeal

Cereals in general, and particularly oatmeals, are considered rather sensitive to oxidation owing to their relatively high fat content. The addition of antioxidants can sometimes prolong the shelf-life of products. The aim of the present study was to investigate how the rate of lipid oxidation of a packaged oatmeal product was affected by the nature and level of antioxidants incorporated in an LDPE film structure. The stability of the product, which was determined by hexanal analysis using GC–MS and by electronic nose analysis, showed very small variations over the chosen storage period. No oxidation, as determined by hexanal levels in the oatmeal, was initiated during storage, but small variations in volatile profile were seen among the samples analysed by the electronic nose. The product stored in the BHT-impregnated LDPE film had undergone the least change during 10 weeks of storage at 20 °C. α-Tocopherol-impregnated LDPE film did not appear to prolong the shelf-life of the oatmeal at all. © 2000 Society of Chemical Industry

The influence of α-tocopherol concentration on the stability of linoleic acid and the properties of low-density polyethylene

In food packaging applications where low-density polyethylene (LDPE) film containing α-tocopherol is used, the antioxidant may have a dual function, i.e. to protect the polymer from oxidative degradation during processing, and to delay the onset of oxidation of the packaged foodstuff during storage. Incorporation of high levels of α-tocopherol into LDPE film was found to inhibit oxidation of a linoleic acid emulsion stored in contact with the film at 6°C. However, the presence of 360 ppm caused changes in mechanical properties and an increase in oxygen transmission. Levels as high as 3400 ppm α-tocopherol also caused yellowing and reduction in crystallinity of the material. Thus, the use of high amounts of α-tocopherol in LDPE, which might be needed in active packaging applications, requires careful consideration of the protective requirements for each specific food and the maintenance of the desired properties of the packaging material. Copyright

Mobility of α‐tocopherol and BHT in LDPE in contact with fatty food simulants

The migration/sorption behaviour of butylated hydroxytoluene (BHT) and a‐tocopherol was studied in packaging material in contact with fatty food simulants. Two low‐density polyethylene (LDPE) films, containing either BHT or a‐tocopherol as antioxidants, were stored in contact with sunflower oil or 95% (v/v) ethanol. The antioxidant content was monitored in the films throughout a period of 7 weeks. The migration of a‐tocopherol into the food simulants was slower than that of BHT. Since a‐tocopherol was transferred from the film to the simulant to a lesser extent, it is considered to be a more stable antioxidant than BHT when used in an LDPE film in contact with 95% ethanol or sunflower oil.

Influence of packaging material and storage condition on the sensory quality of broccoli

The sensory quality of broccoli stored in modified atmosphere packages was studied. Oriented polypropylene (OPP), polyvinyl chloride (PVC) and low-density polyethylene (LDPE) were used as packaging ...

Migration of model contaminants from PET bottles: influence of temperature, food simulant and functional barrier

To simulate post-consumer recycled plastics, selected model contaminants were incorporated into PET bottles using a time saving method. Migration into 3% acetic acid, a cola-type beverage and 95% ethanol was followed during 1 year of storage at 20 and 40°C. Aroma compounds previously found in post-consumer PET material were used as model contaminants. Benzaldehyde was found to migrate to the highest extent. Storage at 40°C affected the bottle material and this might be one reason for the high migration values of these bottles. Migration into ethanol was up to 20 times higher than into 3% acetic acid or a cola-type beverage. Bottles with a functional barrier resisted migration into food simulants even when filled with 95% ethanol and stored for 1 year at 40°C. Differential scanning calorimetry measurements showed that ethanol was interacting with the plastic material. This resulted in a lower glass transition temperature of bottles stored with ethanol compared with bottles stored empty or with other food simulants.

The origin of off-odours in packaged rucola (Eruca sativa)

Rucola (Eruca sativa) was decontaminated and then reinoculated with selected microorganisms. The produce was then stored in three different atmospheres and at two temperatures. The accumulation of off-odours in the packaging headspace was analysed. A dozen compounds were detected by olfactometry but only dimethyl sulphide and dimethyl disulphide were considered to have a strong or moderate intensity. Thus, they were identified as the substances causing an unpleasant smell inside the bags. Inoculation with microorganisms resulted in higher production of off-odours. Samples inoculated with Pseudomonadaceae&Xanthamonadaceae were particularly potent in producing the two sulphides. The off-odour problem was much more prominent in samples that were kept in a packaging material that did not allow gas exchange resulting in oxygen levels below 1%. Higher levels of sulphides were detected at 8°C than at 4°C.

Identification of chemicals, possibly originating from misuse of refillable PET bottles, responsible for consumer complaints about off-odours in water and soft drinks

Mineral water and soft drinks with a perceptible off-odour were analysed to identify contaminants originating from previous misuse of the refillable polyethylene terephthalate (PET) bottle. Consumers detected the off-odour after opening the bottle and duly returned it with the remaining content to the producers. The contaminants in question had thus been undetected by the in-line detection devices (so-called ‘sniffers’) that are supposed to reject misused bottles. GC-MS analysis was carried out on the headspace of 31 returned products and their corresponding reference products, and chromatograms were compared to find the possible off-odour compounds. Substances believed to be responsible for the organoleptic change were 2-methoxynaphthalene (10 bottles), dimethyl disulfide (4), anethole (3), petroleum products (4), ethanol with isoamyl alcohol (1) and a series of ethers (1). The mouldy/musty odour (5 bottles) was caused by trichloroanisole in one instance. In some cases, the origins of the off-odours are believed to be previous consumer misuse of food products (liquorice-flavoured alcohol, home-made alcohol containing fusel oil) or non-food products (cleaning products, petroleum products, oral moist snuff and others). The results also apply to 1.5-litre recyclable PET bottles, since the nature and extent of consumer misuse can be expected to be similar for the two bottle types.

Sorption of β-carotene from solutions of a food colorant powder into low-density polyethylene and its effect on the adhesion between layers in laminated packaging material

Abstract Solutions of different concentrations of β-carotene (1–100 ppm) were stored in laminated packaging material at 4 °C and 25 °C for 8 weeks. Sorption of β-carotene into low-density polyethylene was three times higher at 25 °C than at 4 °C. However, only about 1–2% of the total amount of β-carotene was sorbed at 25 °C. The adhesion between the plastic and aluminium layers of the packaging material decreased during the storage, but total delamination never occurred. The effect was more pronounced at the higher temperature and with increasing concentrations. Advancing and receding contact angles of the aluminium surface increased during the experimental period, indicating surface contamination.

The effect of packaging material on the sensory properties of broccoli.

Three different commercially available polymeric films were studied to determine their effect on the sensory properties of fresh broccoli (Brassica oleracea L. var. Italica cv. ‘Marathon’). The polymer materials investigated were oriented polypropylene (OPP), polyvinyl chloride (PVC) and one low density polyethylene (LDPE) which contained an ethylene absorber. The fresh broccoli was packaged and stored for one week at 10°C or 3 days at 4°C followed by 4 days at 10°C. The oxygen and carbon dioxide concentrations inside the packages were monitored during storage. After storage the broccoli was evaluated according to sensory analyses, i.e. triangle test and quantitative descriptive analysis, by an analytical panel. The panel judged the broccoli according to smell, taste, texture and appearance. The triangle test showed significant differences between the smell of the broccoli samples, stored in the different packaging materials, when cooked. However, no differences between the raw broccoli, stored in the different packaging materials could be detected. The quantitative descriptive analysis showed that the following attributes; fresh smell and taste, chewing resistance, and crispness, differed significantly between the packaged broccoli when cooked. The appearance was shown to be the sensory property of broccoli most affected by the storage conditions, i.e. packaging material used and storage temperature. The results indicated the importance of the packaging material for maintaining the broccoli quality. However, one packaging material that was able to maintain all the studied sensory properties could not be identified. (Less)