Browsing by Subject "hapettuminen"
Now showing items 1-9 of 9
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(2010)The literature review elucidates the mechanism of oxidation in proteins and amino acids and gives an overview of the detection and analysis of protein oxidation products as well as information about ?-lactoglobulin and studies carried out on modifications of this protein under certain conditions. The experimental research included the fractionation of the tryptic peptides of ?-lactoglobulin using preparative-HPLC-MS and monitoring the oxidation process of these peptides via reverse phase-HPLC-UV. Peptides chosen to be oxidized were selected with respect to their amino acid content which were susceptible to oxidation and fractionated according to their m/z values. These peptides were: IPAVFK (m/z 674), ALPMHIR (m/z 838), LIVTQTMK (m/z 934) and VLVLDTDYK (m/z 1066). Even though it was not possible to solely isolate the target peptides due to co-elution of various fractions, the percentages of target peptides in the samples were satisfactory to carry out the oxidation procedure. IPAVFK and VLVLDTDYK fractions were found to yield the oxidation products reviewed in literature, however, unoxidized peptides were still present in high amounts after 21 days of oxidation. The UV data at 260 and 280 nm enabled to monitor both the main peptides and the oxidation products due to the absorbance of aromatic side-chains these peptides possess. ALPMHIR and LIVTQTMK fractions were oxidatively consumed rapidly and oxidation products of these peptides were observed even on day 0. High rates of depletion of these peptides were acredited to the presence of His (H) and sulfur-containing side-chains of Met (M). In conclusion, selected peptides hold the potential to be utilized as marker peptides in ?-lactoglobulin oxidation.
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(2021)Oat has a high content of lipids compared to many other grains. Oat contains lipid hydrolysing enzyme, lipase, and unsaturated fatty acids, which are prone to oxidation. Hydrolytic reactions and oxidation of lipids may cause major quality changes in oats. Oat contains also phenolic antioxidants - tocols, avenanthramides and phenolic acids - that may inhibit lipid oxidation. The aim of this research was to examine how tocols, avenanthramides and phenolic acids act as antioxidants in oat during lipid oxidation. The purpose was to study concentration changes of these compounds in six oat samples in storage. The storage experiment was performed for 12 weeks at 40 °C. Tocols, avenanthramides, phenolic acids and neutral lipids were analysed by liquid chromatography methods after 0, 2, 4, 8 and 12 weeks of storage. Volatile compounds were measured by a solid phase microextraction gas chromatography method. During the storage, volatile compounds, such as hexanal and 2-pentylfuran, were formed especially in groats. Free fatty acids were hydrolysed from triacylglycerols only in groats, because lipase was active in these samples. The α-tocol concentrations of oat samples decreased significantly, 45-77%, in storage. The β-tocotrienol concentrations decreased 34-53%. At the beginning of the storage avenanthramide concentrations showed 20-45% reduction. After that, the concentrations were either stable or increased 10-30%. The phenolic acid concentrations either decreased, increased or were stable during storage. The most significant change was found in unheated groats where the concentration of free caffeic acid increased even 2.6-fold during eight weeks of storage. The loss of α-tocols imply that these compounds are effective antioxidants in oat. This study did not indicate antioxidant activity of avenanthramides and phenolic acids in oat because the changes of these compounds varied in storage. However, the variation of avenanthramide and phenolic acid concentrations may have been caused by their antioxidant activity and release of bound compounds. Thus, further research is needed in order to study the effect of avenanthramides and phenolic acids in oat during lipid oxidation.
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(2020)Beetaglukaanilla on kyky tuoda viskositeettia ja rakennetta nestemäisiin elintarvikkeisiin. Kyseiset reologiset ominaisuudet ovat tärkeitä elintarviketeollisuudessa, fysikaaliset ominaisuudet ovat syynä beetaglukaanin terveysvaikutuksiin. Beetaglukaanin rakenne ei ole kuitenkaan pysyvä. Rakenteen hajoamista tapahtuu prosessoinnin ja säilytyksen aikana. Elintarvikkeiden muilla makromolekyyleillä ja niiden hapettumisherkkyydellä on merkittävä vaikutus beetaglukaanin pysyvyyteen. Aihetta koskevissa tutkimuksissa on todettu, että hapettuneiden makromolekyylien kuten lipidien lisäksi beetaglukaanin mukana kulkeutuvat yhdisteet, kuten mm. fytaatti, voivat vaikuttaa beetaglukaanin hapettumisstabiilisuuteen ja siten vaikuttaa beetaglukaanin teknologiseen ja fysiologiseen toiminnallisuuteen. Työn tavoitteena oli selvittää kauran ja ohran viljauutteiden koostumus eri makro- ja mikrokomponenttien osalta eli määrittää valittujen yhdisteiden pitoisuus näyteliuoksissa analyyttisin menetelmin. Viljauutteiden sisällön analyysistä toivottiin löydettävän selittäviä syy-seuraussuhteita jo aiemmin osittain vastaavista näyteliuoksista tehdyille löydöksille (viskositeetin menetys), koska beetaglukaanin hajoaminen nestemäisissä matriiseissa voi heikentää elintarvikkeiden laatuominaisuuksia. Tämän tutkimuksen näytteistä kaurauutteiden puskuriuutteissa oli eniten fenolisia yhdisteitä, myös lipidejä määritettiin suurimmat pitoisuudet kaurauutteista. Beetaglukaanipitoisuudet vastasivat aikaisempia määrityksiä vastaavista näytemateriaaleista. Raudan osalta tulokset eivät olleet täysin yhteneväisiä, kun ajatellaan yhteyttä aikaisemmin vastaavista näytemateriaaleista tehtyihin analyyseihin koskien viskositeetin menetystä ja radikaalien muodostumista.
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(2020)In this thesis snack production and oats as a raw material for snacks were reviewed. Oat lipid oxidation and the shelf life of snack products made of oats was also considered. The aim of experimental studies was to find out if it is possible to puff baked snacks in the oven with high temperature without using yeast as a leavener. The test was conducted with two different baking temperatures and with and without added yeast. The shelf life of oat-based snacks with spice extract were also studied for 12 months by sensory evaluation. Lipid oxidation was also measured, and the product quality was determined by microbiological tests. Also, two consumer tests (number of panelists n = 30 and n = 118) were made with the snacks. Statistically there were no difference between two baking temperatures in doughs with yeast, but the higher temperature decreased the average error of snack samples heights. Yeast in the dough was significant. Sensory evaluation panel recognised the hidden, freshly baked reference sample from the actual samples at 6 months’ time. The results from the measurements of lipid oxidation on the effect of spice extract on snacks shelf life wasn’t clear and needs further investigation. The products microbiological quality stayed good the whole time monitored.
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(2015)Oats is one of the most cultivated grains in the world. Oat contains 5 to 8 % of lipids, which is a lot compared to many other cereals. Most of the oat lipids are triacylglycerols and about 80 % of its fatty acids are nutritionally significant unsaturated fatty acids. Due to high fat content and high amount of unsaturated fatty acids both the processing of oats and the development of new oat products are challenging. Oat lipids and their reactions during the processing and storage are a significant reason for the changes in oat quality and the unpleasant flavour. It is possible to either decrease or increase the stability of lipids with different processing methods. The objective of this study was to examine oat lipid reactions and stability during the storage. Ravintoraisio Oy gave all the samples for the research. There were seven oat products, which all were differently processed. Samples of different ages of these products were analysed. Short-term storage test was made for four samples, over 16 weeks at 40 °C. At first, all the oat samples were milled to small particles and then total lipids of these products were extracted by accelerated-solvent-extraction. Neutral lipid classes, volatile compounds and tocols were measured from the samples. Neutral lipid classes were analysed by the high performance liquid chromatography method with evaporative light scattering detector. Volatile compounds were measured by a solid phase microextraction method with GC-MS. Tocols were measured by the high performance liquid chromatography method with fluorescence detector. All the oat samples contained about 5 % of lipids. Most of the lipids were still triacylglycerols after a long-term storage. Free fatty acids were detected only from non-heat-treated samples. Content of tocols decreased significantly in oat samples during storage. Tocol content decreased when degree of processing rose. The content of oxidation products of oat lipids, like hexanal, also rose during the storage. Hexanal and 2-pentylfuran were the most abundant volatiles in the samples. The highest amount of oxidation products were found in extrudates which were stored for 16 weeks at 40 °C. Based on the results, storing oat products for 16 weeks at 40°C, corresponds with over one year storage at natural storage temperature. The effects of extrusion and heat treatment have strong influence on reactions of oat lipids and storage stability. The lipids of unprocessed oat grains were the most stable. More information is required to identify the exact reason for off-odors and off-flavours.
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(2017)Kauran ja ohran (1→3)(1→4)-β-D-beetaglukaanit muodostavat viskooseja liuoksia ja kykenevät muodostamaan geelejä. Geeliytymisominaisuuksiin vaikuttavat molekyylin rakenne (kuten sellotriosyyli- ja sellotetrasyyli yksiköiden–suhde), koko, beetaglukaanin pitoisuus liuoksessa ja varastointiaika. Kirjallisuuskatsauksessa käytiin läpi beetaglukaanin viskositeetin ja geeliytymisen merkitystä elintarviketeollisuuden tarpeille sekä terveysvaikutuksille. Lisäksi käytiin läpi tekijöitä, jotka vaikuttavat viskositeettiin ja geeliytymiseen. Työn tavoitteena oli selvittää, miten liukenemislämpötila ohjaa ohran ja kauran beetaglukaanin viskositeettia ja geeliytymistä, kun pitoisuus on pieni (ohra 1 % ja kaura 1,5 %). Lisäksi tarkasteltiin, miten liuoksen hapettaminen vaikutti geeliytymiseen. Beetaglukaania liuotettiin 37, 57 ja 85 ºC:een lämpötiloissa ja sen jälkeen puolet näytteistä hapetettiin 70 mM vetyperoksidilla. Näytteiden viskositeettia ja geeliytymistä mitattiin päivinä 1, 4 ja 7 näytteen valmistamisen jälkeen reometrillä ja lisäksi näytteiden sameutta tutkittiin spektrofotometrillä samoina päivinä. Geeliytymislämpötilan optimoimiseksi kauran betaglukaanille tehtiin vielä lisätestejä 35, 37, 40, 45 ja 50 ºC:ssa. Beetaglukaani liukeni 85 ºC:ssa veteen lähes täysin muodostaen jonkin verran viskooseja liuoksia. Hapettuneiden näytteiden viskositeetit laskivat varastoinnin aikana. Nämä liuokset eivät geeliytyneet varastoinnin aikana. Ohran beetaglukaaneista 57 ºC:ssa liuotettu oli viskoosein, ja kauran beetaglukaaneista 37 ºC:ssa liuotettu oli viskoosein. Ohran beetaglukaani kykeni muodostamaan geeliä ainoastaan, kun se oli liuotettu 57 ºC:ssa, kun taas kauran beetaglukaanilla oli laajempi liuotuslämpötila alue. 37 – 50 ºC:ssa liuenneet kauran beetaglukaanit muodostivat geelin. Hapettamattomien näytteiden muodostamat geelit olivat vahvempia kuin hapetettujen. Tulosten perusteella liuotuslämpötilalla oli suuri vaikutus sekä kauran että ohran beetaglukaanin viskositeettiin ja geeliytymiseen. Optimaalinen liuotuslämpötila viskositeetin ja geeliytymisen kannalta ohran beetaglukaanille oli 57 ºC ja kauran beetaglukaanille 37 – 45 º.
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(2018)Kirjallisuuskatsauksessa käsiteltiin yleisellä tasolla hyönteisten turvallisuutta elintarvikkeena, kotisirkan ja jauhomadon koostumusta sekä niiden proteiineja ja proteiinien toiminnallisia ominaisuuksia. Lisäksi kirjallisuusosassa käsiteltiin lyhyesti proteiinien ja rasvojen hapettumista tämän tutkimuksen näkökulmasta. Tutkimuksen tavoitteena oli tutkia prosessoinnin vaikutusta jauhomadon ja kotisirkan proteiinien hapettumiskäyttäytymiseen emulsiossa sekä vaikutusta lipidien hapettumiseen. Lisäksi tavoitteena oli optimoida kotisirkan ja jauhomadon proteiinien uuttomenetelmä. Proteiinien uuttoa optimoitiin eri menetelmillä ja parhaaksi uuttomenetelmäksi osoittautui molemmille hyönteisille uutto-olosuhteet, jossa uuttoliuoksen pH oli 10 ja NaCl -pitoisuus 0,1 M. Jauhomadon proteiinien uuttoon tarvittiin lisäksi rasvanpoisto ennen proteiinien uuttoa. Molempien hyönteisten proteiineja käsiteltiin lämmöllä (+60 °C) ja entsyymillä (transglutaminaasi). Lisäksi jauhomadon proteiinit käsiteltiin uuton yhteydessä sulfiitilla (Na2S2O5) ruskistumisen estämiseksi. Näistä kaikista käsitellyistä proteiineista sekä molempien hyönteisten käsittelemättömistä liukoisista proteiineista valmistettiin emulsiot, joiden hapettumista seurattiin mittausajankohtina 0, 1, 3 ja 7. Proteiinien hapettumista tutkittiin seuraamalla tryptofaanin hajoamista sekä karbonyylien ja dityrosiinin muodostumista fluoresenssispektroskopisella menetelmällä. Lipidien hapettumista tutkittiin seuraamalla konjugoitujen dieenien muodostumista spektrofotometrisesti. Emulsioiden ulkonäköä seurattiin hapettumiskokeen aikana ja emulsioiden partikkelikoko tutkittiin mittausajankohtana 0. Kotisirkan entsyymikäsitellyistä proteiineista valmistetussa emulsiossa proteiinien hapettumista oli havaittavissa, mutta lipidien hapettuminen oli vähäistä. Jauhomadon entsyymikäsitellyistä proteiineista ja kotisirkan lämpökäsitellyistä proteiineista valmistetuissa emulsiossa proteiinien ja lipidien hapettuminen oli vähäistä. Jauhomadon lämpökäsitellyistä proteiinista valmistetussa emulsiossa konjugoituja dieenejä muodostui enemmän kuin muihin näytteisiin. Tässä emulsiossa muodostui karbonyylejä, mutta tryptofaanin hajoamista ei ollut havaittavissa. Sulfiittikäsittely vaikutti altistavan jauhomadon proteiinit hapettumiselle emulsiossa.
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(2019)The literature part of the study dealt with frying methods, frying fats and oils, chemical and physical changes of frying fats and oils during the frying and analyse methods of frying fats and oils. The aim of the experimental part was to study changes in rapeseed oil quality during continuous frying process during three different frying periods. Especially the effect of day without production during the frying period was studied. Samples, frying oils, were taken every day during the different frying periods. In period one and two there was one day without production. Oils were stored in storage tanks during that time. In third period, there was production on every day. All samples were inspected for colour, odour, viscosity and clearness by visual methods. Also viscosity by rotation viscometer, smoking point, free fatty acids by titration method, fatty acid content and water content of samples was analysed. Based on sensory evaluation, the quality of oil deteriorated over thedays of use. Colour was darker, viscosity was higher and off-odours were sensed. Instrumental analyses indicate same kind of changes; viscosity and free fatty acid were increased and smoking point and amount of unsaturated fatty acid were decreased while frying time was increasing. In literature, also same changes were mentioned. There was changes in fatty acid content during the frying periods. More fatty acids characteristic to meat was detected in oils at the end of period than in fresh oils. Based on these results, oil quality remained acceptable in everyday use for a typical frying period of one week. Difference between fresh oil and used oils was clear but still acceptable. The amount of free fatty acids, and the level of viscosity and smoking points were under the limits applied in Finland. The day without production deteriorated oils quality substantially Reducing the amount of oil in process and having shorter frying periods or more efficient filtering of oils can help to keep the quality of frying oil better.
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(2018)The literature review introduces the rapeseed chemical composition, the rapeseed protein isolate as a novel food ingredient, and protein oxidation. Rapeseed is an economically important oilseed crop since it is one of the largest sources of vegetable oil in the world. Rapeseed expeller is a protein-rich by-product of canola oil extraction. The main use of this protein-rich by-product is animal feed. However, it could be potentially utilized in the food industry, for example, as a source of protein in plant protein products, as a texture-improving ingredient in bakery products or as an alternative for animal proteins. We need more protein for human nutrition, and thus it is important to find new plants that can be used as protein sources. This way we can reduce environmental stress. Because the production process of rapeseed protein expeller already exists, it is a good new potential protein source. Protein and lipid oxidation are significant factors when food and nutrition quality are examined. The objective of this study was to optimize the protein extraction method and to examine the oxidation of rapeseed proteins and the lipid oxidation in two different rapeseed expellers. A few parameters, including extraction solvent (0.1 M and 1 M NaCl), pH (8 and 10), extraction time (4 h and overnight) and the removal of oil, were tested and the parameters that gave the biggest acquisition of soluble proteins were chosen for the experiment. The oxidation of rapeseed protein expeller was measured based on the loss of tryptophan fluorescence and the formation of carbonyls and dityrosine by using fluorescence spectrometry and based on the formation of hexanal by using the headspace gas chromatography method. Protein oxidation was measured in two different ways: in the rapeseed protein expeller during three months and in the extracted protein solution during seven days. The chosen extraction parameters were pH 8, 0.1 M NaCl solution and overnight extraction. The soluble protein amounts of the two rapeseed expeller samples were different after extraction, but this could be explained by the batches’ slightly different chemical compositions, especially their different cruciferin and napin ratios. During both the 7-day and 3-month oxidations, the tryptophan fluorescence decreased. During the 3-month oxidation, the formation of carbonyls increased and no hexanal was detected in any of the rapeseed expeller samples which were measured with headspace gas chromatography. The temperature and preservation time had a considerable effect on the protein oxidation in both the 7-day and 3-month oxidation tests, when only the loss of tryptophan was considered as an oxidation marker. The results revealed that fluorescence spectroscopy is a potential method for investigating the protein oxidation in the rapeseed protein expeller by using the loss of tryptophan and the formation of carbonyls as oxidation markers.
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