Jens Petter Wold

The effect of headspace oxygen concentration and color of light on photo‐oxidation and degradation of photosensitizers in butter was studied. Butter samples were stored under 0%, 0.4%, 0.8%, 1.6%, 3.0%, 5.0%, 21% oxygen, and exposed to violet, green or red light. Storage time was 36 h. Degree of photo‐oxidation was measured by a trained sensory panel. Photobleaching of six different photosensitizers was estimated based on front face fluorescence excitation and emission landscapes and spectral curve resolution (parallel factor analysis). The higher oxygen concentration, the more sensory degraded were the samples. Violet light resulted in slightly higher degrees of photo‐oxidation than green and red light for low oxygen concentrations. Bleaching rate and course as function of O₂ concentration differed between the photosensitizers. It is suggested that the rate of photobleaching is a balance between type I and type II photoreactions.

Human health may be improved if dietary intakes of selenium and omega-3 fatty acids are increased. Consumption of broiler meat is increasing, and the meat content of selenium and omega-3 fatty acids are affected by the composition of broiler feed. A two-way analyses of variance was used to study the effect of feed containing omega-3 rich plant oils and selenium enriched yeast on broiler meat composition, antioxidation- and sensory parameters. Four different wheat-based dietary treatments supplemented with 5% rapeseed oil or 4% rapeseed oil plus 1% linseed oil, and either 0.50 mg selenium or 0.84 mg selenium (organic form) per kg diet was fed to newly hatched broilers for 22 days. The different dietary treatments gave distinct different concentrations of selenium and fatty acids in thigh muscle; one percent linseed oil in the diet increased the concentration of the omega-3 fatty acids 18:3, 20:5 and 22:5, and 0.84 mg selenium per kg diet gave muscle selenium concentration at the same level as is in fish muscle (0.39 mg/kg muscle). The high selenium intake also resulted in increased concentration of the long-chain omega-3 fatty acids EPA (20:5), DPA (22:5) and DHA (22:6), thus it may be speculated if high dietary selenium might have a role in increasing the concentration of EPA, DPA and DHA in tissues after intake of plant oils contning omega-3 fatty acids. Moderate modifications of broiler feed may give a healthier broiler meat, having increased content of selenium and omega-3 fatty acids. High intakes of selenium (organic form) may increase the concentration of very long-chain omega-3 fatty acids in muscle.

In this study, fluorescence excitation and emission matrices and multivariate curve resolution (PARAFAC) were used to detect and characterize active photosensitizers spectrally in butter. Butter samples were packed under high (air) and low oxygen (a-like molecule, and two unidentified tetrapyrrols. By estimation of relative concentrations, we could follow how each sensitizer was photodegraded as function of wavelength, oxygen level, and time. The degradation rate of protoporphyrin, hematoporphyrin, chlorophyll a, and one of the tetrapyrrols correlated well (0.83−0.91) with the formation of sensory measured oxidation. The results suggest that mainly type I photoreactions were responsible for the degradation of photosensitizers in both high and low oxygen atmosphere. Type II photoreactions (generation of singlet oxygen) were involved in the oxidation of butter stored in air. The study shows that PARAFAC modeling of fluorescence landscapes is an excellent tool for studying photooxidation in complex systems. Keywords: Photooxidation; photosensitizer; fluorescence spectroscopy; PARAFAC; butter

This paper describes a multi-spectral imaging near infrared (NIR) transflectance system developed for on-line determination of crude chemical composition of highly heterogeneous foods and other bio-materials. The system was evaluated for moisture determination in 70 dried salted coalfish (bacalao), an extremely heterogeneous product. A spectral image cube was obtained for each fish and different sub-sampling approaches for spectral extraction and partial least squares calibration were evaluated. The best prediction models obtained correlation R² values around 0.92 and root mean square error of cross-validation of 0.70%, which is much more accurate than today's traditional manual grading. The combination of non-contact NIR transflectance measurements with spectral imaging allows rather deep penetrating optical sampling as well as large flexibility in spatial sampling patterns and calibration approaches. The technique works well for moisture determination in heterogeneous foods and should, in principle, work for other NIR absorbing compounds such as fat and protein. A part of this study compares the principles of reflectance, contact transflectance and non-contact transflectance with regard to water determination in a set of 20 well-defined dried salted cod samples. Transflectance and non-contact transflectance performed equally well and were superior to reflectance measurements, since the measured light penetrated deeper into the sample.

Front face autofluorescence from meat products was measured to elucidate the method's ability to measure and predict lipid oxidation. Three sample sets were studied: turkey meat with added aldehydes, raw and heat‐treated turkey meat, and meat loaf at different process steps. Multivariate regression was used to correlate against sensory assessed rancidity, volatile compounds (GC‐MS), and TBARS. Results verified that the increase in fluorescence during storage originates from aldehydes reacting with the meat matrix. Fluorescence modeled sensory assessed rancidity at the same accuracy as volatile compounds (R = 0.9), but was superior to TBARS. Front face fluorescence seems to be a powerful tool for nondestructive analysis of oxidation progress in meat products.

The purpose of this paper is to demonstrate the potential of solid-sample fluorescence spectroscopy in nondestructive assessment of light-induced oxidation in different dairy products such as Swiss cheese, cream cheese, and sour cream. Analytical and quantitative spectral properties of fluorescence were elucidated by use of principal component analysis with designed experiments involving different levels of air and light exposure. A significant reduction in fluorescence intensity at approximately 525 nm, and a corresponding increase in the region 415 to 490 nm as a result of illumination was observed on all the products. The effect was ascribed to photodegradation of riboflavin. Variation in two smaller peaks at approximately 620 nm and 630 nm was an interaction effect between exposure to light and air. A pronounced interaction effect between light and air produced intense blue fluorescence and off-flavors on Swiss-like Jarlsberg cheese. High correlations (0.83 to 0.93) between fluorescence spectra and sensory measured off-flavors were obtained for cream cheese. Results indicate that solid-sample fluorescence can be used as a nondestructive and rapid tool to measure the degree of light-induced degradation of riboflavin as well as sensory properties connected to storage of dairy products. Images of fluorescence can be used to visualize the intensity and propagation of this process. The simplicity and rapidity of the method offer rich opportunities for efficient evaluation of factors affecting light-induced oxidation in dairy products, such as packaging materials, light sources, exposure time, and temperature.

To develop a rapid method to assess lipid oxidation, autofluorescence spectra (excitation wavelengths 365, 380, and 400 nm) from large samples (17 cm2) of minced poultry meat were collected by an optical system to determine directly lipid oxidation level. The same samples were also measured by 2‐thiobarbituric acid method (TBARS). High correlations could be made between the TBARS method and autofluorescence spectra, especially those from 380 nm excitation. Partial least squares regression resulted in a root mean square error of 0.15 (R = 0.87) for chicken meat and 0.24 (R = 0.80) for mechanically recovered turkey meat. Classification analysis between fresh (TBARS < 0.25) and rancid (TBARS > 0.25) samples was done with high success rates. Autofluorescence spectroscopy might be well suited for rapid on‐line determination of lipid oxidation level in minced poultry meat.