Browsing by Subject "haihtuvat yhdisteet"

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  • Mäenpää, Jenni (Helsingin yliopisto, 2020)
    Wines are treated to ensure their quality and preservation in the winemaking process. Treatments also have their drawbacks. Premium winemakers have often avoided filtration because it is supposed to cause a loss of taste. Sulfurization of wine is important, for example, for microbiological quality, but it is assumed to reduce the fruity aroma of wines. The purpose of the literature section was to investigate in general the effects of the wine-making process on the volatile compounds of wines. The interest was to find out what happens in winemaking and what compounds are formed at different stages of the process. The literature section also looked at volatile compounds, their analytics and SPME technology. The aim of the experimental part of the work was to develop a research method using headspace-solidphasemicroextraction-gaschromatography-massspectrometry (HS-SPME-GC-MS) technology and to find out the aroma composition and possible differences of the receiving sample and the bag-in box (BIB) -packaged wine. Indicator compounds for volatile compounds were determined from Chardonnay and Cabernet Sauvignon wines using the HS-SPME-GC-MS method developed for the study of Cabernet Sauvignon wine. In the optimization of the method, the functionality of SPME fibers, the GC temperature program and the sample preparation were studied. Receipt, tank, and BIB packaging samples were collected for examination of the wines. The samples were analyzed by HS-SPME-GC-MS and the results were processed by principal component analysis (PCA) as well as other statistical methods. Receipt and BIB packaging samples from Cabernet Sauvignon wine were not divided into clear groups based on PCA. The model best describing the changes in the compounds was achieved with the profile of volatile compounds: ethyl acetate, 1-propanol, isoamyl alcohol, 2-methylbutanol, butanoic acid ethyl ester, isoamyl acetate, hexanol, hexanoic acid, octanoic acid ethyl ester and octanoic acid. In Cabernet Sauvignon wine, almost all the amounts of volatile compounds remained fairly constant as the process progressed. In 1-propanol, ethyl ester of butanoic acid and ethyl ester of octanoic acid, a decrease in the amount was observed between the receipt sample and the BIB packaging sample. In contrast, the amount of 2-methylbutanol and octanoic acid increased when receiving and BIB packaging samples were compared. Receipt and BIB packaging samples of Chardonnay wine were distinguished by PCA. The model best describing the changes in the compounds was achieved with the profile of volatile compounds: ethyl acetate, isoamyl alcohol, 3-methylbutanol, 2-methylbutanol, butanoic acid ethyl ester, isoamyl acetate, hexanol, hexanoic acid, benzene alcohol, octanoic acid ethyl ester, octanoic acid ethyl ester, octanoic acid ethyl ester. The amounts of volatile compounds studied in Chardonnay wine remained fairly constant. Octanoic acid ethyl ester, benzyl alcohol and decanoic acid decreased as the process. The results of the study show that the wine processing process affects the flavorings of Cabernet Sauvignon and Chardonnay wine. The HS-SPME-GC-MS method showed a reduction in several compounds, but previous studies have shown that this change has not been detected by sensory evaluation.
  • Mustonen, Otto (Helsingin yliopisto, 2018)
    Tiivistelmä/Referat – Abstract In food matrices usage of legumes is challenging due to formation of volatile compounds during storage and processing. These volatile compounds form beany flavors, which cause sensory problems in food matrices. Because the formation of volatile compounds in legume matrices is quite quick, it is supposed that enzymatic oxidation is significant when lipids are oxidized in legume matrices. The literature review of this thesis focused on the mechanisms of lipid oxidation in plants, enzymes and formation of volatile compounds in food matrices. The aim of the experimental part was to investigate how volatile compounds are formed from different faba bean and lupine cultivars by endogenic enzymes using different lipid substrates. The activity of lipoxygenase and incubation conditions were optimized at first and those conditions were used to analyse the actual samples. The main legume matrix in this study was faba bean (4 cultivars) and two lupine cultivars were also investigated. The selected legumes were pretreated by grinding the dried pods of legumes in certain particle size. Legume flours were mixed with water to prepare slurries to extract the endogenic enzymes of legume matrices. Due to lipoxygenase’s significant role in enzymatic oxidation of lipids the optimum pH-level of lipoxygenase was determined by using UV/VIS-spectrophotometer. The optimum pH-level for lipoxygenase was found at the pH 6. Optimization and formation of volatile compounds was determined by using HS-SPME-GC-MS-method. In addition, the activity of lipase and product specificity of lipoxygenase (formation of hydroperoxides) were determined. In both legume matrices the pH-optimum of lipoxygenase was at 6 and all the actual samples were measured at that pH. Quantitatively and qualitatively the widest spectrum of volatile compounds was formed when using linoleic acid as a substrate. The spectrum of volatile compounds included different alcohols, ketones, aldehydes and furans. The amounts of hexanal were at the highest when using linoleic acid as a substrate and the lowest when using α-linolenic acid as a substrate. When using trilinolein and rapeseed oil as substrates aldehydes and ketones were the only volatile compounds which were formed. Saponification of rapeseed oil improved the formation of the volatile compounds. In addition, from the saponified rapeseed oil a wider spectrum of volatile compounds were formed when compared to untreated rapeseed oil. The lipoxygenases of faba bean and lupine were shown to form different types of hydroperoxides from linoleic acid: the faba bean produced more 13-hydroperoxides than 9-hydroperoxides and lupine produced only 13-hydroperoxides. Used method when measuring the formation of free fatty acids of legume matrices did not revealed the activity of lipase. On the other hand, this result only tells that lipase activity couldn’t be measured by using this particular method and other methods could reveal lipase activity on those legume matrices. Both of the legume matrices formed different kinds of volatile compounds from different lipid substrates in certain reaction conditions. When those volatile compounds are formed in foods containing legume matrices they lower the sensory value of those foods. The formation volatile compounds in food matrices containing legumes is very plausible due to food matrices pH-level (many of them are at neutral) and usage of suitable lipid substrates and reaction conditions. Inactivation of enzymes can be obtained for example by heating, which could at the same time lower the nutritional value of foods.
  • Kekäläinen, Sonja (Helsingin yliopisto, 2017)
    Elintarvikepakkauksen tehtävänä on suojata elintarviketta ja pidentää sen säilyvyyttä. Aktiivisessa elintarvikepakkauksessa pakkaus tai sen komponentit sekä elintarvike ovat vuorovaikutuksissa toistensa kanssa. Polysakkaridiaerogeelit ovat huokoisia ja kevyitä materiaaleja, joista ollaan kehittämässä uusia pakkausmateriaaleja. Polysakkaridiaerogeeleillä on kyky sitoa tai vapauttaa haluttuja yhdisteitä. Ne ovat vedellä tai vesipohjaisella liuoksella paisuneita geelejä ja ovat hydrofiilisiä eli vesihakuisia materiaaleja. Aerogeelit valmistetaan hydrogeeleistä poistamalla geelin nestemäinen osuus, esimerkiksi haihduttamalla vesi pois hydrogeelistä. Heksanaali on aldehydi, jota muodostuu rasvojen hapettumisen yhteydessä. Se on herkästi haihtuva yhdiste, jolla on havaittu olevan voimakkaita antimikrobisia ominaisuuksia patogeenisiä mikro-organismeja vastaan. Heksanaalin käyttömahdollisuuksia elintarvikepakkaussovelluksissa on tutkittu vihannesten ja hedelmien säilyvyyden parantajana. Sen sijaan heksanaalin ja muiden haihtuvien aldehydien tuotosta pakkausmateriaaleissa, saati niiden hyödyntämisestä aerogeeleissä ei ole vielä tutkimustietoa. Erittäin haihtuvien orgaanisten yhdisteiden käyttöä pakkausmateriaalissa rajoittaa haihtuvien yhdisteiden toiminta, joka on melko ohimenevää, ja se vaatisi jatkuvaa aineiden lisäämistä pakkaukseen. Aiheesta tehtyjen esikokeiden perusteella tutkimusaihetta voidaan kuitenkin pitää lupaavana. Työn tavoitteena oli kehittää aerogeelimatriisi heksanaalin tuottamiseksi, jotta tulevaisuudessa menetelmää voitaisiin hyödyntää elintarvikepakkauksissa. Työn kokeellisessa osassa selvitettiin, voidaanko heksanaalia tuottaa polysakkaridiaerogeeleissä auringonkukkaöljystä, entsyymikatalysoidun hapettumisen avulla. Työssä selvitettiin myös valmistusaineiden ja substraattien komponenttisuhteet. Tässä työssä aerogeelit valmistettiin kuusen galaktoglukomannaanista (GGM) pakkaskuivauksen avulla. Heksanaalia muodostui, kun matriisissa oleva lipoksigenaasientsyymi katalysoi hapettumisreaktiota, jonka seurauksena heksanaalia muodostui ja vapautui. Heksanaalin vapautumista aerogeelimatriisista määritettiin kiinteäfaasimikrouuton ja kaasukromatografi-massaspektrometrin (SPME-GC-MS) avulla. Heksanaalin muodostumista ja vapautumista seurattiin säilytyskokeen avulla. GGM-aerogeelejä säilytettiin lämpötiloissa 4 ˚C, 10 ˚C ja 20 ˚C, ilman suhteellisen kosteuden ollessa <10 %, sekä ilman suhteellisissa kosteuksissa <10 %, 54 % ja 76 %, lämpötilan ollessa 20 ˚C. Toistokoe suoritettiin ilman suhteellisen kosteuden ollessa <10 % ja lämpötilassa 20 ˚C. Lipoksigenaasientsyymin määrä säilytyskokeen näytteissä oli 100 yksikköä öljygrammaa kohden ja lipaasientsyymin määrä oli 20 yksikköä öljygrammaa kohden. GGM-aerogeelien heksanaalin muodostumista ja vapautumista seurattiin yhteensä 14 vuorokauden ajan. Heksanaalia muodostui ja vapautui kaikissa tutkituissa olosuhteissa. Säilytyskokeen perusteella voidaan todeta, että ilman suhteellisilla kosteuksilla ei ole juurikaan vaikutusta heksanaalin muodostumiseen ja vapautumiseen, kun taas eri lämpötiloilla vaikutusta oli selkeästi havaittavissa. Lämpötila-säilytyskokeessa heksanaalia vapautui eniten lämpötilassa 20 ˚C. Sen sijaan matalimmissa lämpötiloissa, 4 ˚C ja 10 ˚C, heksanaalia vapautui hieman vähemmän. Tuloksista voidaan päätellä, että heksanaalia muodostui ja vapautui GGM-aerogeeleistä riittävä määrä pidentämään kasvisten säilyvyyttä 14 vuorokauden ajan. Tulevaisuudessa sovellusta voisi tutkia myös käytännössä sijoittamalla auringonkukkaöljyemulsiota sisältävää GGM-aerogeeliä kasvista sisältävään elintarvikepakkaukseen.