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Unigunde Antone, Vita Šterna, Jeļena ZagorskaINVESTIGATIONS INTO THE ENHANCEMENT<strong>OF</strong> COW’S MILK OXIDATIVE STABILITYLosses in vitamin B 2content in milk during storage in direct sunlight (mean±SD)Table 2Exposure time, h 1.5 3.0Experimental Control Experimental ControlGroupsTG1 TG2 CG TG1 TG2 CGDecrease in34.87 ± 2.54 35.31 ± 2.04 35.50 ± 0.87 41.60 ± 0.65 47.18 ± 0.81 44.61 ± 0.37vitamin B 2, %A more pronounced positive tendency that cowfeed supplementation with carotenoids additives haspotential to increase the stability of vitamin B 2againstphoto-oxidative degradation in milk was seen in ourprevious investigation, showing that the vitamin B 2photo-oxidative stability was higher in milk obtainedfrom carotenoids-supplemented cows, saving 10-11%of vitamin B 2during 1.5 h period, and 5-8% during3 h period of milk exposure to sunlight (Antone et al.,2011).However, the average losses of vitamin B 2inour study were higher – 34.87-35.50% and 41.60-47.18% compared to the results from our previousinvestigations, namely, 10.03-21.22% during first1.5 h and 15.66-23.48% during 3-h period of themilk exposure to sunlight (Antone et al., 2011). Thedifferences in results can also be explained by thedifferences in light intensity (Bosset et al., 1994)and in the initial antioxidative capacity of milk aswell (Walstra et al., 1999). The losses of vitamin B 2in fluorescent light are also significant. Unpackagedpasteurized milk exposed to cool white fluorescentlight for 7 h undergoes riboflavin losses of over75% (Bosset et al., 1994). For the further research itwould be valuable to take into consideration that thechanges in vitamin B 2content should be monitoredearlier – during the first hour of sunlight exposure dueto its extremely high sensitivity to photo-oxidation,thus possibly allowing detecting more pronouncedeffects from cow feed supplementation with differentcarotenoids supplements.As mentioned previously, the photo-oxidativedegradation is the main cause of riboflavin losses. Thisshould be considered when choosing the packagingmaterials for food products containing vitamin B 2,among which milk and dairy products are rich andexcellent natural dietary sources (Eitenmiller et al.,2008). Milk storage in packages made from glass orother transparent materials is quite often practicedin Latvia. Cardboard packaging is also frequentlyused, and while it is not transparent it is certainly notalways impermeable to light (Walstra et al., 2006).The intensity of light and lengths of storage timeof products containing riboflavin and other photosensitivevitamins should also be chosen cautiouslyto minimize the losses of nutritional value of foodproducts.The oxidative stability of milk fat measured as PVchangesThe oxidative stability of milk fat was measuredby changes in PV during storage at the temperatureof 60 °C. PV is a sensitive indicator of oxidative andphotooxidative changes in fats and oils. PV showsthe concentration of primary oxidation products –hydroperoxides and peroxides – in the fat, howeverthese are highly unstable substances producingsecondary oxidation products – mainly carbonylcompounds (Bosset et al., 1994). In our test, the maincause of oxidation was the influence of temperature(60 °C) and the partial contact of fat with air, but for ahalf of samples – also the contact with sunlight at thebeginning of the ageing process.As seen from Figure 2, the oxidation process ofmilk fat that was not affected by light was very slow.During the 25-day period, only slow changes in thePV or induction period were observed showingthe relatively high oxidative stability of butter oil.Significant (p 25 days. Such agood stability of milk fat can be explained by the factthat it has a relatively low polyunsaturated fatty acidcontent and high proportion of saturated fatty acidscompared to many other edible fats. Milk fat alsocontains natural fat-soluble antioxidants – carotenoidsand vitamin E (tocopherols and tocotrienols) thatincreases the induction period (MacGibbon andTaylor, 2006). Vitamin E functions as the primaryantioxidant and as the peroxy free radical scavenger.It is the primary, lipid-soluble, autooxidation chainbreakingaction mechanism antioxidant that combinesactions with other lipid- and water-soluble antioxidantsto provide an efficient defense against free radicaldamage (Eitenmiller et al., 2008). The inductionperiod usually is very slow until hydroperoxides areformed. Initially antioxidants are consumed; afterResearch for Rural Development 2012167
INVESTIGATIONS INTO THE ENHANCEMENT<strong>OF</strong> COW’S MILK OXIDATIVE STABILITYUnigunde Antone, Vita Šterna, Jeļena Zagorskathis has been achieved, peroxides are first liberatedand subsequently broken down to form perceptibleamounts of flavour products (Walstra et al., 1999).Concerning the samples of milk fat exposedto light – the oxidative deterioration was muchfaster. At the beginning fat oxidation possessedwith low intensity (induction period) followedby rapid increase in hydroperoxide concentration(Fig. 3) accordingly to the theory (Kamal-Eldin andYanishlieva, 2005). For each type of fat, the end ofthe induction period was determined by the tangentmethod. The tangents as linear function lines of thephase of active hydroperoxide formation (B) of CGand TG1, respectively, were drawn, and the crossingpoints with corresponding linear function lines ofinduction period (A) were found.The established induction periods are showed inTable 3. The induction periods were 10.97 and 12.03days, for the CG and TG1 respectively. The inductionperiod of TG2 was > 14 days, because the phase ofactive hydroperoxide formation (exponential phase)during the 14-day period was not observed yet.Induction periods of milk fat samples from both trialgroups were longer than induction period of controlgroup’s milk fat, and a tendency of the impact ofantioxidant protection on fat stability through theenrichment of cow’s diet by its antioxidant contentwas evident.Peroxide value, % of iodine0.0140.0120.0100.0080.0060.0040.0020.0000 2 4 6 8 10 12 14 16 18 20 22 24 26Storage daysTG1 TG2 CGLinear (TG1) Linear (TG2) Linear (CG)y = 0.0002x + 0.0027R² = 0.4749y = 0.0002x + 0.0027R² = 0.4624y = 0.0002x + 0.0025R² = 0.5575Figure 2. Peroxide value changes of milk fat stored in the dark.0.60TG1 (A)0.50TG2 (A)CG (A)Peroxide value, % of iodine0.400.300.20TG1 (B)CG (B)Linear (TG1 (A))Linear (TG2 (A))Linear (CG (A))y = 0.0007x + 0.0095y = 0.0021x - 0.0006y = 0.0007x + 0.01250.10Linear (TG1 (B))y = 0.2175x - 2.59770.001 2 3 4 5 6 7 8 9 10 11 12 13 14Linear (CG (B))y = 0.1773x - 1.9244Storage daysFigure 3. Peroxide value changes of milk fat exposed to light:(A) – the induction period, (B) – the phase of active hydroperoxide formation.168 Research for Rural Development 2012
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Volume No. 1Annual 18th Internation
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Research for Rural Development 2012
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ContentsFOOD SCIENCESVETERINARYMEDI
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AGRICULTURAL SCIENCES (CROP SCIENCE
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Mihails Vilcāns, Jūlija Volkova,
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Mihails Vilcāns, Jūlija Volkova,
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Berit TeinEFFECT OF ORGANIC AND CON
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Methane producing bacteria use only
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according to calculations the metha
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CHANGES IN SUGAR CONTENT OF WINTERO
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PERENNIAL GRASSES FOR BIOENERGY PRO
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IMPACT OF SLURRY APPLICATION METHOD
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IMPACT OF SLURRY APPLICATION METHOD
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IMPACT OF ORGANIC PRODUCT EXTRACTS
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IMPACT OF ORGANIC PRODUCT EXTRACTS
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COMBUSTION ABILITY OF ENERGY CROP P
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COMBUSTION ABILITY OF ENERGY CROP P
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RESEARCH OF OREGANO (ORIGANUMVULGAR
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RESEARCH OF OREGANO (ORIGANUMVULGAR
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INFLUENCE OF SOIL MODIFICATION ON C
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INCIDENCE OF POSTHARVEST ROT OF CRA
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INCIDENCE OF POSTHARVEST ROT OF CRA
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PERSPECTIVES ON TRUFFLE CULTIVATION
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FACTORS AFFECTING GOAT MILK YIELDAN
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MILK UREA CONTENT AS INDICATOR FEED
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REHYDRATION KINETICS OF DRIED LATVI
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FOOD SCIENCESPreliminary RESULTS of
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PRELIMINARY RESULTS OF 1-METHYLCYCL
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FOOD SCIENCESSensory PROPERTIES and
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SENSORY PROPERTIES AND CHEMICAL COM
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THE SUITABILITY OF DIFFERENT ROWANB
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Page 117 and 118: THE SUITABILITY OF DIFFERENT ROWANB
Page 119 and 120: CHEMICAL COMPOSITION OF NEW TYPE AG
Page 125 and 126: FOOD SCIENCESINFLUENCE OF GENOTYPE
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Page 133 and 134: ROOT VEGETABLES FROM LATVIA:QUANTIT
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Page 145 and 146: RHEOLOGICAL PROPERTIES OF TRITICALE
Page 151 and 152: acceptance and preference especiall
Page 153 and 154: CONSUMERS’ ATTITUDE TOWARDS AVAIL
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Page 157 and 158: PHYSICAL - CHEMICAL CHARACTERIZATIO
Page 159 and 160: PHYSICAL - CHEMICAL CHARACTERIZATIO
Page 161 and 162: FOOD SCIENCESTHE INFLUENCE OF DIFFE
Page 163 and 164: THE INFLUENCE OF DIFFERENT SELENIUM
Page 165 and 166: FOOD SCIENCESINVESTIGATIONS INTO TH
Page 167: INVESTIGATIONS INTO THE ENHANCEMENT
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Page 173 and 174: INFLUENCE OF PACKAGING CONDITIONSON
Page 175 and 176: INFLUENCE OF PACKAGING CONDITIONSON
Page 177 and 178: FOOD SCIENCESFATTY ACID COMPOSITION
Page 179 and 180: FATTY ACID COMPOSITION OF THE MEAT
Page 181 and 182: FATTY ACID COMPOSITION OF THE MEAT
Page 183 and 184: ANTIMICROBIAL RESISTANCE OFANIMAL P
Page 189 and 190: VETERINARY MEDICINETHE SURVIVAL OF
Page 191 and 192: THE SURVIVAL OF LISTERIA MONOCYTOGE
Page 197 and 198: VETERINARY MEDICINEMicrobiological
Page 199 and 200: MICROBIOLOGICAL QUALITY OF COWS’
Page 205 and 206: PORCINE CIRCOVIRUS-2 IMPACT ON THEM
Page 213 and 214: AORTIC LUMEN DIAMETER AND BLOODPRES
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PHYSICAL MODEL OF TRACTOR IMPLEMENT
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SOLID FUEL BOILER AUTOMATION FOR BR
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INVESTMENT COSTS OPTIMIZATION OFMUL
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INVESTMENT COSTS OPTIMIZATION OFMUL
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DYNAMIC MODEL OF BIOCHEMICAL NETWOR
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DYNAMIC MODEL OF BIOCHEMICAL NETWOR
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EDUCATIONAL SCIENCESCHILDREN WITH S
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CHILDREN WITH SPECIAL NEEDS FAMILY
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