Oxidative Stability of Polyunsaturated Edible Oils Mixed With Microcrystalline Cellulose

The oxidative stability of mixtures of edible oils containing polyunsaturated fatty acids (PUFA) and microcrystalline cellulose (MCC) was investigated. The mixtures studied consisted of oils of either camelina (CAM), cod liver (CLO), or salmon (SO) mixed with either colloidal or powdered MCC. A 50:50 (w/w) ratio of oil:MCC resulted in an applicable mixture containing high levels of PUFA edible oil and dietary fiber. The oxidative stability of the formulated mixtures and the pure oils was investigated over a period of 28 days. The peroxide value (PV) was assessed as a parameter for primary oxidation products and dynamic headspace gas chromatography mass spectrometry (GC/MS) was used to analyze secondary volatile organic compounds (VOC). CAM and the respective mixtures were oxidatively stable at both 4 and 22 °C during the storage period. The marine oils and the respective mixtures were stable at 4 °C. At 22 °C, an increase in hydroperoxides was found, but no increase in VOC was detected during the time-frame investigated. At 42 °C, prominent increases in PV and VOC were found for all oils and mixtures. Hexanal, a common marker for the degradation of n-6 fatty acids, propanal and 2,4-heptadienal (E,E), common indicators for the degradation of n-3 fatty acids, were among the volatiles detected in the headspace of oils and mixtures. This study showed that a mixture containing a 50:50 ratio of oil:MCC can be obtained by a low-tech procedure that does not induce oxidation when stored at low temperatures during a period of 1 month.     

Minimizing photooxidation in pasteurized milk by optimizing light transmission properties of green polyethylene films

The effect of different amounts of transmitted green light on photooxidation in pasteurized milk was studied. Five different green films produced with combinations of pigments and additives to minimize exposure to harmful wavelengths with regard to photosensitizers (400–450 and 600–650 nm) were evaluated. In addition, a non-colored transparent film and an orange film were compared with 1 selected green film. Pasteurized milk (3.9% fat) was packed in an air atmosphere and exposed to light for 14, 20, 26, and 32 h at 4°C under the different films. Samples stored in the dark were control samples. The results showed that the most-effective green film had low overall light transmission, and also almost completely blocked light wavelengths shorter than 450 nm and wavelengths longer than 600 nm, which prevented photooxidation of riboflavin and chlorophyllic compounds. Chlorophyll degradation was highly correlated with sensory properties (coefficient of determination = 0.80–0.94). To preserve milk quality, total blocking of all visible light would be preferable. If total blocking is not feasible, then light transmission for wavelength below 450 nm and above 650 nm should be minimized (e.g., less than 5%). The newly developed green film can be used as a prototype for protection of dairy products to reduce the degradation of photosensitizers.     

Quantitative determination of saturated-, monounsaturated- and polyunsaturated fatty acids in pork adipose tissue with non-destructive Raman spectroscopy

The composition of dietary fat has received increased attention during the recent years because it influences human health. Seventy seven samples from pork adipose tissue and melted fat from the same tissue were measured with Raman spectroscopy. Gas chromatography analysis was conducted as reference. Iodine values (IV) ranged from 58.2 to 90.4 g iodine added per 100 g fat. Polyunsaturated fatty acids (PUFA) ranged from 7.8% to 31.7% and monounsaturated fatty acids (MUFA) from 35.2% to 51.5% of total fatty acids. When applied on pre-processed spectra of melted fat, partial least square regression (PLSR) with cross-validation gave a correlation coefficient (R) = 0.98, and root mean square error of cross-validation (RMSECV) = 1.4 for IV, using 3 PLS factors in the model. PUFA gave R = 0.98 and RMSECV = 1.0% of total fatty acids, using 5 PLS factors. MUFA were predicted with R = 0.96 and RMSECV = 1.0% of total fatty acids, using 9 PLS factors. On adipose tissue a model with 3 PLS factors gave R = 0.97 and RMSECV = 1.8 for IV. For PUFA, a model with 3 PLS factors gave R = 0.95 and RMSECV = 1.5% of total fatty acids. For MUFA a model with 6 PLS factors gave R = 0.91 and RMSECV = 1.5% of total fatty acids. The results indicate the feasibility to use Raman spectroscopy as a rapid and non-destructive method to determine IV, PUFA, MUFA and saturated fatty acids (SFA) measured directly on pork adipose tissue and in melted fat from the same tissue.     

Long-term stability of a Raman instrument determining iodine value in pork adipose tissue

The stability of a calibration model from a non-destructive Raman instrument during a period of three years was studied. A calibration model created on a dataset measuring pork adipose tissue in 2005 determining iodine value (IV), was transferred to a dataset measuring pork adipose tissue three years later in 2008. During these three years the fibre optic cable had been changed and the output of the laser was reduced to 60% compared with the power in 2005. The samples were also taken from different parts of the carcass. Aligning the peak positions and pre-processing with multiplicative scatter correction together with a selection of wavelengths/wavenumbers gave, for IV, a correlation coefficient of 0.95 for measured versus predicted IV of the 2008 samples. The accuracy expressed as root mean square error of prediction was 2.04 g iodine added to 100 g of melted fat with 6 partial least squares factors for the 2008 samples. This study shows that it is possible, with minor modifications, to transfer the model from spectra measured three years later on the same instrument. It is concluded that a quantitative use of Raman instruments are robust over time.     

Oxidative properties of lactoferrins of different iron-saturation in an emulsion consisting of metmyoglobin and cod liver oil

Lactoferrins (LFs) at iron-saturation 8 (native) and 100%, respectively, were present in an oil-in-water (O/W) emulsion composed of 5% (w/v) cod liver oil (CLO) and metmyoglobin (metMb) in 50 mM phosphate buffer at pH 6.0. Initially both LFs acted as antioxidants and reduced initial peroxide formation, but after 48 h holo LF revealed the most peroxides but the least trienes. Native LF (0.8 mg/ml) gave the highest (p < 0.05) amounts of lipid derived volatiles after 48 h incubation at 4 °C. Both LFs gave similar increases in adducts to metMb with time. The most extensive aggregation induced by radicals or peroxides was found for native LF. The results pointed at reactions at the O/W interphase as highly influential for lipid and protein oxidation kinetics. Added ascorbic acid (1 mM), however, behaved as an antioxidant in the pro-oxidative oil-in-water emulsion system and prevented lipid degradation and protein adductation as well as protein aggregation.     

Preference mapping of salmon–sauce combinations: The influence of temporal properties

Food–food combinations are complex stimuli where the dynamic nature of sensory interactions plays an important role for perception and acceptance. The aim of this study was to investigate if TDS provides additional insight about drivers of liking compared to DA in a preference mapping context. A trained sensory panel performed DA and TDS on six different samples (combinations of salmon and culinary sauces), and sixty-one consumers rated acceptance for the same samples. In addition to TDS SCORES, this study introduces the use of extracted parameters based on dominance information from TDS; the area of dominance based on the integrated area under the dominance curves and the number of dominant sensations and blends within a specified time period. Results from preference mappings showed that the TDS approaches generally provided similar but less detailed information regarding drivers of liking and disliking compared to DA. Moreover, with the use of the extracted TDS parameters, it was possible to identify the time of dominance of certain attributes and the number of perceived sensations and blends in specific time periods as potential drivers of liking and disliking. The results also showed that TDS has a potential to provide complementary information about the dynamic nature of sensory interactions in food–food combinations compared to DA.     

A comparative study of fatty acid profiles in ruminant and non‐ruminant milk

This is a comprehensive study of fatty acid (FA) profiles in milk from bovine, caprine, ovine, asine, and equine species. Milks from these species are universally common as constituents in a variety of different food and dairy products. We have obtained structural information on FAs, and discussed their correlation to health effects. The extracted fat from all species were derivatized to FA methyl esters for analysis by GC‐MS. Large differences in the lipid content and FA composition between ruminants and non‐ruminants were observed. Ovine milk showed the highest lipid content of all the animals tested, both ruminants and non‐ruminants. Among the ruminants, bovine milk was richer in saturated FAs (69.7%) than ovine‐ and caprine milk (57.5 and 59.9%, respectively). Ovine milk contained the highest amounts of monounsaturated FAs (39.1%) and also odd‐ and branched‐chain FAs (5.5%). Milk from the monogastric animals, mares and donkeys, were highest in polyunsaturated FAs with a content of 19.3 and 14.2%, respectively. The assumed health negative trans FAs were analyzed to be highest in the ruminant milk (0.7–1.0%). Milk from these species contained also the highest amount of the health beneficial CLA (0.4–0.7%). Practical applications: This is a comprehensive study of milk from five species analyzed under identical conditions. The different fatty acids and their derivatives are increasingly important components because of the contradictory reports on positive and negative effects on human health. New information on the composition of milk from different species is of great importance. The results may give valuable information to producers and nutritional advisors on the consumption of milk and milk products.     

Mixing properties and rheological characteristics of dough used to make potato‐cereal soft wraps

We have studied mixing, rheology and stability of potato‐cereal flour doughs. These were prepared using samples of two varieties of cooked and cold‐stored potatoes. Dependent on variety a minimum duration of 24–48 h cold‐storage was required. Dough mixing torque plateau was inversely related to potato water content. This should be <79 g/100 g. It was also necessary to have a stable dough mixing torque plateau of >2 Nm at a specific total mechanical energy input of 18–22 kJ kg^?1. The resting temperature of the dough was also inversely related to its strength (plateau elastic modulus at time zero). Target dough strength should be about 25 kPa in a bob‐cup. Above 15 °C it decreased as a function of time and within 1 h it became too sticky for commercial processing. At 4 °C the dough remained stable. Sufficient potato starch retrogradation is a pre‐requisite to make optimal potato‐cereal flour dough for commercial processing.     

Effect of different colored filters on photooxidation in pasteurized milk

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 N₂) and exposed to light for 20 h at 4°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 N₂ 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 N₂ correlated well with sensory properties related to photooxidation (R² = 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.