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Abstract

The degradation of coffee cream quality, in different packaging and exposed to different lamps, was evaluated. Coffee cream is often retailed in packaging highly permeable to light and oxygen with high surface-to-volume ratio; therefore, riboflavin-containing coffee cream is sensitive to photooxidative reactions. Light-emitting diodes (LEDs) or sodium vapour lamps show lower emissions in the critical range for riboflavin-containing products, creating less excitation energy for riboflavin compared with fluorescent lamps. Parameters investigated were the oxygen content and the hexanal concentration in the packaging, as well as riboflavin degradation. The impact on these quality attributes was shown to be higher for coffee cream packaged in light- and oxygen-permeable packaging and when exposed to fluorescent lamps. The quality of dark-stored references was not affected during storage indicating light-induced quality deterioration. The application of LEDs or sodium vapour lamps proved able to maintain the quality of light exposed coffee cream for a longer time.

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Herbivore damage is generally detrimental to plant fitness, and the evolu- tionary response of plant populations to damage can involve either increased resistance or increased tolerance. While characters that contribute to resistance, such as secondary chem- icals and trichomes, are relatively well understood, characters that contribute to a plant's ability to tolerate damage have received much less attention. Using Helianthus annuus (wild sunflower) and simulated damage of Haplorhynchites aeneus (head-clipping weevil) as a model system, we examined morphological characters and developmental processes that contribute to compensatory ability. We performed a factorial experiment that included three levels of damage (none, the first two, or the first four inflorescences were clipped with scissors) and eight sires each mated to four dams. We found that plants compensated fully for simulated head-clipper damage and that there was no variation among plant families in compensatory ability: seed production and mean seed mass did not vary among treat- ments, and sire X treatment interactions were not significant. Plants used four mechanisms to compensate for damage: (1) Clipped plants produced significantly more inflorescences than unclipped plants. Plants produced these additional inflorescences on higher order branches at the end of the flowering season. (2) Clipped plants filled significantly more seeds in their remaining heads than did unclipped plants. (3) Clipped plants, because they effectively flowered later than unclipped plants, were less susceptible to damage by seed- feeding herbivores other than Haplorhynchites. (4) In later heads, seed size was greater on clipped plants, which allowed mean seed size to be maintained in clipped plants. Although there was genetic variation among the families used in this experiment for most of the characters associated with compensation for damage (seed number, mean seed size, mean flowering date, length of the flowering period, and branching morphology), in analyses of these characters, no sire X treatment interactions were significant indicating that all of the families relied on similar mechanisms to compensate for damage.
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Riboflavin, vitamin B₂, and flavins (as riboflavin building blocks or degradation products) are efficient photosensitizers inducing oxidative damage to light-exposed tissue and food by substrate-dependent mechanisms, for which protection is offered by specific nutrients. Phenolic and N-heterocyclic amino acids and their peptides and proteins deactivate triplet-excited state riboflavin in diffusion controlled processes, efficiently competing with deactivation by oxygen, resulting in direct (so called Type I) protein degradation through electron transfer or proton-coupled electron transfer. In light-exposed tissue, such often long lived protein radicals may as primary photoproducts initiate lipid and vitamin oxidation. In contrast, for lipid systems, oxygen deactivation of triplet-excited state riboflavin, resulting in formation of singlet oxygen, is under aerobic conditions faster than direct deactivation by lipids, which otherwise under anaerobic conditions occurs as hydrogen atom transfer from polyunsaturated lipids to triplet riboflavin. Singlet oxygen adds to unsaturated lipids and forms lipid hydroperoxides as primary lipid oxidation products or oxidizes proteins (Type II mechanism). Carotenoids seem not to deactivate triplet riboflavin, while chromanols like vitamin E and plant polyphenols are efficient in such deactivation yielding protection of proteins and lipids by these phenols. Indirect protection against the triplet reactivity of riboflavin is further important for polyphenols as riboflavin singlet excited state quenchers in effectively preventing riboflavin intersystem crossing to yield the reactive triplet state. Riboflavin photosensitization becomes critical for degradation of proteins, unsaturated lipids, and folate, thiamine, ascorbate and other vitamins during light exposure of food during storage. For skin, eye and other tissue exposed to high intensity light, dietary polyphenols like flavonoids are important in direct protection against photosensitized oxidation, while dietary carotenoids may yield protection through inner-filter effects, through scavenging of radicals resulting from Type I photosensitization, and through quenching of singlet oxygen formed in Type II photosensitization. Both carotenoids and polyphenols accordingly counteract the degenerative effect induced by riboflavin exposed to light, although by different mechanisms.
Article
Milk packaged in glass bottles overwrapped with iridescent films (treatments blocked either a single visible riboflavin [Rb] excitation wavelength or all visible Rb excitation wavelengths; all treatments blocked UV Rb excitation wavelengths) was exposed to fluorescent lighting at 4 degrees C for up to 21 d and evaluated for light-oxidized flavor. Controls consisted of bottles with no overwrap (light-exposed treatment; represents the light barrier properties of the glass packaging) and bottles overwrapped with aluminum foil (light-protected treatment). A balanced incomplete block multi-sample difference test, using a ranking system and a trained panel, was used for evaluation of light oxidation flavor intensity. Volatiles were evaluated by gas chromatography and Rb degradation was evaluated by fluorescence spectroscopy. Packaging overwraps limited production of light oxidation flavor over time but not to the same degree as the complete light block. Blocking all visible and UV Rb excitation wavelengths reduced light oxidation flavor better than blocking only a single visible excitation wavelength plus all UV excitation wavelengths. Rb degraded over time in all treatments except the light-protected control treatment and only minor differences in the amount of degradation among treatments was observed. Hexanal production was significantly higher in the light-exposed control treatment compared to the light-protected control treatment from day 7; it was only sporadically significantly higher in the 570 nm and 400 nm block treatments. Pentanal, heptanal, and an unidentified volatile compound also increased in concentration over time, but there were no significant differences in concentration among the packaging overwrap treatments for these compounds.
Article
The effect of different colored filters and atmospheres on photooxidation and quality in milk was studied. Pasteurized bovine milk (3.9% fat) was packed in 2 different atmospheres (air and N(2)) and exposed to light for 20 h at 4 degrees C under 8 transparent filters with different light transmission properties. The following transparent, noncolored, and colored filters based on polyethylene terephthalate (PET) were used: noncolored (PET), noncolored with 2 different UV-block regions, yellow, green, amber, orange, and red. Control samples were stored in darkness and in a carton. Sensory evaluation showed off flavors significantly increased in milk stored under all filters compared with the control samples. Variation in atmosphere resulted in significant differences in formation of rancid flavor in milk stored under different filters. Milk samples stored in N(2) underwent the most sensory deterioration under orange and red filters, whereas milk samples stored in air were most deteriorated under noncolored filters. According to the oxidation compounds measured by gas chromatography, milk samples stored under noncolored and orange filters were highly oxidized, whereas red, green, and amber filters offered better protection against photooxidation. Fluorescence spectroscopy was used to examine the degradation of photosensitizers (riboflavin, protoporphyrin, and chlorophyllic compounds) in the milk samples. Degradation of protoporphyrin and chlorophyllic compounds in N(2) correlated well with sensory properties related to photooxidation (R(2)=0.75-0.95). The study indicates that protoporphyrin and chlorophyllic compounds were effective photosensitizers in milk. To avoid photooxidation in milk, it is therefore important to protect it against light from the UV spectrum as well as light from the entire visible region.
Article
Sumario: 1. Basic constants, units and conversion factors -- 2. Nomenclature, symbols and terminology -- 3. Physical constants of organic compounds -- 4. Properties of the elements and inorganic compounds -- 5. Thermodinamycs, electrochemistry and kinetics -- 6. Fluid properties -- 7. Biochemistry and nutrition -- 8. Analytical chemistry -- 9. Molecular structure and spectroscopy -- 10. Atomic, molecular and optical physics -- 11. Nuclear and particle physics -- 12. Properties of solids -- 13. Polymer properties -- 14. Geophysics, astronomy and acoustics -- 15. Practical laboratory data -- 16. Health and safety information -- Appendix A: Mathematical tables
Article
The effects of exposure of slices of Havarti cheeses to monochromatic light of wavelengths 366 nm, 405 nm, and 436 nm, respectively, were studied by tristimulus colorimetry, solid-phase microextraction gas chromatographic analysis of volatiles, and open-end fluorescence spectroscopy. Having determined the photon fluxes of the three wavelengths by ferrioxalate actinometry, it was possible to quantify the effects of light exposure in an absolute manner. For all analyses, the most severe effects were caused by visible light, leading to colour bleaching, change in hue, riboflavin degradation, and formation of the secondary oxidation products hexanal, 1-pentanol, and 1-hexanol. Apparent quantum yields for formation of hexanal and 1-pentanol were found to be insignificantly different for 405 nm and 436 nm exposures, having values of (3-5) x 10(-5) mol x einstein(-1) and (9-13) x 10(-5) mol x einstein(-1), respectively. These compounds were not formed when exposed to 366 nm light. In contrast, 1-hexanol was formed when exposing cheese to all three wavelengths, resulting in apparent quantum yields of (2-6) x 10(-5) mol x einstein(-1). The results obtained are discussed in relation to the interplay between inherent product colorants, light sources, and transmission characteristics of the packaging materials.
Article
Degradation of the potential photosensitizers, riboflavin, chlorophyll, and porphyrin, in Danbo cheese by monochromatic light of wavelength 366, 436, or 546 nm was studied. Three cheeses were investigated, two conventional (16% fat and 25% fat) and one "organic" (25% fat). The effect of illumination was measured by fluorescence spectroscopy and analyzed using multiway and multivariate data analysis. Riboflavin was found to degrade only by 436 nm light, whereas chlorophylls and porphyrins also were influenced by 436 and 546 nm light. The organic cheese had the largest chlorophyll content both before and after similar light exposure, and no change in chlorophyll of this cheese was observed for any of the illumination wavelengths. Upon light exposure of the cheeses, volatile compounds were formed, as analyzed by gas chromatography-mass spectrometry (GC-MS). The relative concentrations of methyl butanoate, 1-pentanol, benzaldehyde, 2-butanone, 2-heptanone, and butyl acetate were found to weakly correlate with the surface fluorescence intensity. 1-Pentanol and the ketones are secondary lipid oxidation products, consistent with a chemical coupling between photosensitizer degradation and formation of volatile lipid oxidation products.
Testing of plastics -Determination of gas transmission rate -Part 3: Oxygen specific carrier gas method for testing of plastic films and plastics mouldings
  • W Cladman
  • S Scheffer
  • N Goodrich
  • M W Griffiths
Cladman, W., Scheffer, S., Goodrich, N., & Griffiths, M. W. (1998). Shelf-life of milk packaged in plastic containers with and without treatment to reduce light transmission. International Dairy Journal, 8, 629e636. DIN.. (1998). Testing of plastics -Determination of gas transmission rate -Part 3: Oxygen specific carrier gas method for testing of plastic films and plastics mouldings. DIN 53380-3. Berlin, Germany: Beuth Verlag GmbH.