Browsing by Subject "Food Technology"

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  • Koljonen, Paula (Helsingfors universitet, 2017)
    Aflatoxins are harmful compounds found in food and feed. The literature review of this thesis looked at aflatoxin M1 (AFM1) found in milk and its occurrence, significance and prevention methods using lactic acid bacteria (LAB). Furthermore, the assay methods of aflatoxins and the factors affecting the analysis were discussed. The aim of the experimental work was 1) to investigate the ability of five LAB strains to bind AFM1 in vitro and 2) to investigate how different matrixes affect the assay of AFM1 and to evaluate the feasibility of the selected ELISA kit for the study. In the first phase of the study the AFM1 concentrations of three different matrixes were analyzed using ELISA when known concentrations of the AFM1-standardsolution were added (0, 20 ja 40 ppt). In the second phase of the study the abilities of five LAB strains to bind AFM1 in UHT skimmed milk and MRS-broth were investigated. The bacterial suspensions were incubated at +32 °C for one hour, and the AFM1 concentration in the matrixes were 50, 15 and 10 ppt. The unbound AFM1 concentrations of the supernatants were analyzed from the samples using ELISA. The unbound AFM1 concentrations were converted to the proportional portion of the bound AFM1. In this study, statistically significant differences were observed in the abilities of the LAB to bind AFM1. The viable cells of strain B2 27 (Lb. plantarum-, pentosus- or paraplantarum) were the best binders of AFM1. They removed 43.7 % AFM1 in UHT skimmed milk, where the AFM1 concentration was 15 ppt. Unlike in previous studies viable cells bound AFM1 better than the heat-killed cells. The used ELISA kit was a sensitive method for analyzing low concentrations of AFM1, but at higher concentrations the assay results were inaccurate. The nonspecific interaction due to the components of the matrixes had to be taken into account when the results were reviewed. In the future, it may be possible to utilize the LAB strains, such as B2 27 for reducing AFM1 the concentration in milk and probably in other foodstuffs. There is a need to develop a practical application which can be used in the binding of AFM1 using lactic acid bacteria and thus reduce the bioavailability of AFM1.
  • Ninios, Aliki Ilona (Helsingfors universitet, 2013)
    Alkaline phosphatase (ALP) is an endogenous enzyme found in milk, which is inactivated at higher temperatures than vegetative bacteria and is thus used as an indicator of a successful pasteurisation. The ability of ALP to reactivate allows it to be found in milk products that are claimed to be pasteurised. The aim of this Master‘s thesis was to understand the reactivation behaviour of ALP in order to ascertain whether high levels found in milk products are correlated to a normal reactivation property of the enzyme or other possible reasons, such as a failed pasteurisation or contamination. This work also aimed to define the mean ALP activities found in specific commercial milk products and their deviation from the acceptable levels. Another scope was to determine the freeze stability of ALP to define its appropriateness for post-stored analysis. Lastly, the examination of ALP location in milk fat membrane globules was examined to interpret the variation of enzyme activity levels in products of different fat content. The experimental part of the Master‘s thesis was divided into three parts. The first part included the record of ALP activities of different commercial Finnish milk products which are analysed in different groups according to their fat content and product type. The second part concentrated on the heat-treatment of milk samples at different time-temperature relationships and followed the reactivation behaviour of ALP. The total micro-flora was taken into consideration in order to observe any relation between the increased ALP activities and microbial growth. ALP activities were measured by a fluorimetric method, a quick three minute method which has the advantage of being more accurate compared to colourimetric methods. The third part examined the fraction in which ALP activities are found in milk after separation and its freeze stability when stored at -79 ºC. Commercial cheeses showed a high ALP activity in Emmental thermised cheeses and an activity less than 10 mU/g in other cheese types and pasteurised cheeses. In commercial milks, UHT treated and those closer to expiration date, high ALP activities were found, while pasteurised milks had low activities below the higher acceptable levels. The reactivation property of milk samples that were heat-treated in ALP was not related with the microbial growth and was quicker when the milk samples were heat-treated at higher temperatures. After the separation of cream from whole milk samples, ALP activity was found in the skim milk part. In conclusion, ALP activities did not decrease significantly following freeze storage for a few days showing its stable freeze properties.
  • Suryanarayanan, Tilak (Helsingfors universitet, 2015)
    The objective of the thesis was to investigate the effect of carbohydrates on solubility, emulsifying, gelling and water holding properties of proteins. Faba bean is a readily available pulse crop with high protein content similar to soy bean and there is a lot of potential for a novel, high protein fermented gel product to be made from a pulse crop like faba bean. This is mainly due to its remarkable nutritional properties, functional properties and low cost, the demand for faba bean protein ingredients will grow. The current study was an attempt to develop pulse protein based products – emulsion (milk-like) and emulsion gel (yogurt-like) from faba bean. It seeks to expand the field of application of faba bean protein based products. Faba bean was pretreated, dehulled and milled. The flour was made into suspensions and the starch in faba bean was subjected to amylolytic treatments (addition of alpha amylase and glucoamylase) to breakdown the starch into smaller particles. These treated suspensions were then homogenized to obtain emulsion. A protein based gel network was produced with the gelation of amylolytically treated faba bean proteins. The emulsion properties, specifically droplet size, stability and activity were tested by PAMAS Particle Counter System. Light microscopy was applied to reveal the microstructure of emulsion and emulsion gel. Emulsion gel texture properties were studied by texture analysis. The emulsions were relatively stable over a period of a month and had white ‘milk’ like appearance. The emulsion gels prepared (amylolytic treatment) had slightly higher water holding capacities than the control A (entire starch present) and control B (starch removed by filtration) emulsion gels. Texture analysis of the emulsion gels showed that more force was required by probe to penetrate the yogurt produced from amylolytically treated samples and less force was required to penetrate the yogurt produced from controls A and B. The yield of the emulsion gels were higher for the amylolytically treated samples. It can be concluded that amylolytic treatment has increased the water holding capacity and also resulted in stronger gel systems.
  • Wickman-Viitala, Tiina (Helsingin yliopisto, 2020)
    There is growing concern about the world population growth and the sufficiency of protein resources. Edible insects could be an alternative protein source for human beings. The aim of this master thesis was to examine the sensory characteristics of a new home cricket (Acheta Domesticus) product and understand the attitudes of consumers towards edible insects. The aim was to investigate the impact of consumer familiarity with edible insect food products on purchase intention and expected liking. The roles of media trust and purchase activism were expected to affect the behavior of consumers. Besides these four indicators also two more were added. These were food neophobia scale and innovativeness. The data on consumer attitudes and perception towards insect food was collected by using an electronic form that was sent to different mailing lists. Total of 167 respondents were gathered, 141 women and 63 men. 53 participants attended the sensory analysis tests on the beginning of the year 2020, ages 18 – 62. The analysis of the data was done with SPSS Statistics version 25. The findings of this study indicate that consumer familiarity contributes to purchase activism, purchase intention and expected liking. In this study the media trust did not contribute. Food neophobia scores correlated negatively to the intention to buy, expected liking and willingness to recommend the product. Innovativeness correlated positively to intention to buy and expected liking, and as expected, innovativeness correlated negatively to food neophobia scores. As people learn more about the ecological and nutritional benefits of edible insects, their attitudes towards insect food become more positive and they are more willing to try and taste insect products. The new home cricket product, PANNU Sirkka by GRiiDY, turned out to be quite suitable for Finnish consumers taste. On the just-about-right scale (1–4) the average score was 3,3 – 3,8 of all the assessed attributes. Many of the open responses mentioned the product to be ‘tasty, delicious, surprisingly good and crispy’, for instance. To overcome the preconceptions of western consumers, there should be more occasions to try and taste insect food. Marketing efforts are best targeted to consumers who are neophilic and innovative and encourage them to be the early adopters of insect food.
  • Kelloniemi, Jarmo (Helsingfors universitet, 2009)
    The objectives of this study was to investigate the cause of the local whiteness in AURAÒ blue cheese and to find the way which reduces the white cheeses. It was studied if white cheeses have a compact or open structure. White cheeses were classified as compact and open. Scanning electron microscopy was performed on compact, open and mouldy cheeses. Factors which cause compact cheese were also studied. At the beginning of blue cheese manufacturing, citrate was analysed at different time points in different vats. The aim was to make compact cheese in one of the trials. Cheese curd was broken before and after moulding. Alternative factors including the effect of addition of salt to the vat on reducing the amount of white cheeses was also studied. Other variables were the speed of the drying belt, heating of vat, the amount of vat whey and the different moulds were also studied. In addition it was studied how separation of whey affects to the amount of compact cheeses in the drying belt. Microbiological and chemical analyses as well as density and texture measurement were performed on the trials. Most of the white cheeses were compact and the small amount of white cheeses had an open structure. The compact cheeses had less mould and yeast than the mouldy cheeses. The pH was lower and the amount of free amino acids was less in the compact cheeses than the mouldy cheeses. The compact cheeses were more dense than the mouldy cheeses. Measurements from texture analyser showed that the hardness of compact cheese were greater and the fracturability of compact cheese was lower than the hardness or fracturability of mouldy cheese. There were no differences in the amount of citrates between days or vats. Broken cheese curd before moulding caused a more compact structure. The addition of salt in the vat did not affect the white cheeses. The compact cheeses decreased when the speed of the drying belt was reduced. With the use of the new mould, less compact cheeses were produced than with older mould. The removal of water from cheese curds is logarithmic the longer they are on an open drying belt. The compact cheese also decreased logarithmically when cheese curds were on drying belt from zero to ten seconds. There was a greater amount of compact cheeses after moulding in the vat.
  • Sirén, Heli (Helsingin yliopisto, 2020)
    Milk foam is an essential part of coffee drinks such as cappuccinos. The foaming properties of milk can change during its shelf life. Milk used in coffee usually contains at least 2 % fat which can deteriorate its foaming properties. UHT milk can lose its sensory and foaming properties during its shelf life. In this thesis the change of properties of UHT-treated coffee milk called Barista milk were investigated. Barista milk is a commercial lactose free, homogenized milk meant to use with coffee. It has 2,0 % of fats and 3,5 % of proteins. The preservation of UHT barista milk was studied when milk was 4, 5, 6 and 7,5 months old. The foaming properties of barista milk were evaluated with automated foaming system. The volume of foam and its stability were measured as volume in a measuring glass. The structure of foams was also photographed and analyzed from photos. Nowadays plant-based drinks are important options for milk. Selected oat drinks for coffees were studied with same foaming methods as milk samples. The oat drink samples were kept in room temperature, fridge (+6 °C) and + 30 °C storage conditions. The tests were made when samples were 4, 8 and 10 months old. Barista milk as evaluated also with sensory evaluations. The sensory properties of barista milk were measured by tasting the milks referred to a fresh reference milk. Sweetness, bitterness, intensity of cooked flavor and fullness were evaluated from milks and cappuccino drinks made from the studied milks. In addition, a professional barista foamed the milks to makes cappuccinos and the drinks were evaluated. The preservation of milk did not affect its foaming properties or foam stability significantly. The foaming temperature affected the volume of foam more than the age of the milk. There was a slight change in the bubble structure of milk. The bubble structure was more uneven with older milk than fresh milk. Oat drinks foamed more, and the foams were more stable in all samples compared to milks of same age. The effect of foaming temperature was less meaningful with oat drinks than with milks. The sensory properties of milk did not change significantly during the study. The biggest change was the decline of cooked flavor in samples tasted as milk. The same decline was not detected when the milks were tasted as cappuccino drinks. An increase of bitterness was detected in the cappuccinos made by a barista when the milk was 6 months old. According to these results the shelf life of barista milk can be lengthened from 4 months to 5 months.
  • Kolmonen, Aino (Helsingin yliopisto, 2019)
    Elintarvikkeiden komponenttien välillä olevat vuorovaikutukset voivat vaikuttaa elintarvikkeiden valmistusprosesseihin, säilyvyyteen ja terveysvaikutuksiin. Tärkkelys ja beetaglukaani molemmat sitovat vettä, ja niiden vaikutus gluteenittoman leivän rakenteen muodostumisessa on olennaista. Gluteenittoman leivän suurin haaste on rakenteen säilyminen paiston jälkeen, mikä aiheuttaa hävikkiä. Vuorovaikutuksien tuntemisen ansiosta prosessit voitaisiin optimoida niin, että gluteenittoman leivän rakenne säilyisi pidempään hyvänä. Kokeellisen työn tavoitteena oli selvittää reologisilla menetelmillä, onko tärkkelyksen ja beetaglukaanin geeliytymisessä eroja, kun näiden muodostamien seosten kuumennusaikaa ja lämpötilaa vaihdeltiin.Vuorovaikutuksia tutkittiin mittaamalla seosten viskositeettia Rapid Visco Analyzerilla (RVA), ja geelien reologiaa mitattiin taajuuspyyhkäisymittauksella. Beetaglukaania sisältävän tärkkelysliuoksen RVA:lla saadun liisteröitymiskäyrän huippuviskositeetti ja loppuviskositeetti olivat korkeampia kuin ilman beetaglukaania valmistetun tärkkelysliuoksen. Beetaglukaania ja tärkkelystä sisältävillä geeleillä oli myös vahvempi rakenne kuin pelkästä tärkkelyksestä valmistetulla geelillä. Beetaglukaanin ja tärkkelyksen liuottaminen yhdessä ei kuitenkaan johtanut vahvemman geelin muodostumiseen, kun liuosta kuumennettiin levyllä noin kahden tunnin ajan. Tutkimuksessa haluttiin tutkia tarkemmin sitä, miten liuotusaika ja -lämpötila vaikuttavat geelirakenteeseen. Kahden tunnin ajan 85 ˚C lämpötilassa liuotetun beetaglukaanin ja gelatinoidun tärkkelyksen sekoituksesta valmistetun geelin ominaisuuksia vertailtiin 15 minuuttia korkeintaan 37 ˚C:ssa liuotetun beetaglukaanin ja liisteröidyn tärkkelyksen sekoituksesta valmistettuun geeliin, ja havaittiin ettei beetaglukaanin parempi liukeneminen johtanut vahvemman geelin muodostumiseen. Tutkimuksen tulokset viittasivat siihen, että laimean beetaglukaaniliuoksen geeliytymisen taustalla on osittainen liukeneminen, mikä on todistettu jo aiemmissa tutkimuksissa. Tutkimuksen tuloksien soveltamisesta gluteenittoman leivän valmistuksessa voitaisiin saada hyötyä, kun rakenne säilyisi hyvänä pidempään prosessien optimoinnin seurauksena.
  • Xiao, Kun (Helsingin yliopisto, 2015)
    Lactobacillus rhamnosus GG is a lactic acid bacterium that is widely used as probiotic products in the dairy industry. To gain insights into the genome stability of the L. rhamnosus GG in the human gastrointestinal tract and the possible adaption mechanism under different stresses, we first examined the genotype and phenotype of the L. rhamnosus GG grown over 1000 generations under various stresses, including bile salts, osmotic stress or shearing forces. Immunoblotting analysis of L. rhamnosus grown over 1000 generations showed that the production of mucus-binding pili by L. rhamnosus GG was the most impaired when exposed to bile salts. Complementary PCR screening of 13 highly variable chromosomal regions in GG confirmed that the pilus gene cluster had been lost when exposed to bile stress over time. In vitro bile-induced genomic changes observed in GG possibly reflects the genome plasticity and stability of GG in the human intestinal tract. Still, we showed that these changes only occurred after more than 100 generations, a period of time relatively long compared to the observed time of persistence and transit of GG in the intestinal tract. Although damages and stresses may be caused by bile salts, L. rhamnosus GG still has the ability to tolerate bile salts. The resistance mechanism is still unclear but, based on previous studies, we identified one ABC transporter encoded by the gene operon called tauABC that may be involved in bile resistance. In an effort to demonstrate its function, a tauB-null mutant derivative was generated and phenotypically characterized in terms of metabolic, signaling and functional properties. The data revealed that the tauB-null mutant significantly grow slower than L. rhamnosus GG wild-type strain in the presence of ox bile extracts. Additional screenings using various bile conjugates specifically revealed that two compounds of bile salts, i.e. taurodeoxycholic and taurochenodeoxycholic acid, may be processed by the TauABC transporter, contributing at least partially to the tolerance of GG to bile salts. Overall, we showed that bile salts constitute an important stress factor for GG that causes genomic alterations, although it has bile tolerance mechanisms to bile, such as the newly-characterized tauABC operon.
  • Räisänen, Heidi (Helsingfors universitet, 2016)
    Sustainable development and fluctuating petroleum prices encourage manufacturing packaging materials in a more natural and cost-effective way. Green economy utilizes renewable raw materials from the nature which can be used in larger scale applications such as packaging industry. Barrier properties can be enhanced by manufacturing multilayer structures with a coating made of organic materials such as cellulose nanofibrils (CNF). With CNF it is possible to provide barrier and mechanical improvement to packaging material at low added cost. Together with hydrophobic films (e.g., HDPE, LDPE) also the low water vapor permeability and heat sealing properties can be enhanced. The aim of this thesis was to utilize CNF as a barrier layer for bio-based flexible food packaging pouches. A study consisted of examining 1-layer bio-HDPE film, 2-layer bio-HDPE/CNF film and 3-layer HDPE/CNF/LDPE film and testing their permeability (for oxygen, water vapor and aroma), sealability, tensile strength, influence of irradiation and aroma compounds (clove), and suitability for modified atmosphere packaging, MAP (with hazelnuts). The 2- and 3-layer multilayer films provided very good oxygen barrier under dry conditions, although aroma exposure increased the oxygen permeability rates. Pouches made of the 2-layer film were the most feasible for MAP, even though the 3-layer film would also have been an alternative if the film quality had been optimal. The oxidation of fatty acids in hazelnuts could be slowed down by using multilayer structure including CNF barrier under modified atmospheric conditions. This study helps to verify the feasibility of the bio-based multilayer films as a new food packaging material, and demonstrates the use of CNF as a high-barrier layer in a laminate. Bio-HDPE/CNF/bio-LDPE multilayer has potential for utilizing it in flexible food packaging pouches if the manufacture process is standardized leading into homogeneous film quality.
  • Korjus, Emmi (Helsingfors universitet, 2017)
    Gas permeabilities of films used in food packaging must be well known to ensure the best conditions for packed food products. In addition to oxygen and carbon dioxide permeability as such their ratio affects the choice of packaging materials. The CO2/O2 ratio of petroleum derived plastics is normally under 6:1 but that of bio-based films is less known. The literature review of this study focused on different sources of bio-based raw-materials and their chemical structure. The aim of the experimental study was to measure oxygen and carbon dioxide permeabilities of different bio-based films and to identify the CO2/O2 ratio. Another point of interest was the realiability of used carbon dioxide permeation analyzer which was assembled from an old oxygen permeation analyzer and gas chromatography. Three of the used film types were prepared in laboratory scale from Konjac glucomannan, starch and hydroxypropyl starch with 10 % or 40 % of sorbitol (of the dry matter) due to a reduction of porosity of materials. Other bio-based films were obtained from VTT (cellulose nanofibrils, hydroxypropyl xylan, cellulose derivative, cellophane and polyglycolic acid). Almost all the films had low oxygen permeabilities (OP<2.8 [cm3 µm]/[m2 d kPa]) and replicate results did not vary much. The cellulose derivative films had higher OP of 120 (cm3 µm)/(m2 d kPa). The carbon dioxide permeabilities showed more variation and were clearly higher (CO2P was 0 to 978 [cm3 µm]/[m2 d kPa]). In addition films including 40 % of sorbitol leaked more often. The ratio of CO2/O2 varied between 7:1–329:1. Most of the measured bio-based films are suitable for packaging food products, whose preservation depends on the permeability of carbon dioxide through the packaging more than that of oxygen. Excellent applications can be found among fruits and vegetables, whose maturing have to be controlled during storage. High CO2/O2 ratios were due to rather different chemical structures of the studied bio-based films and therefore the determination of a definite CO2/O2 ratio was not possible (unlike with petroleum based films). The magnitude of carbon dioxide permeabilities were similar to those reported in literature but further research with the assembled analyzer is needed to ensure its realiability.
  • Tasiyana, Diana Tendai (Helsingin yliopisto, 2015)
    The shelf life of ESL milks and pasteurized creams is limited by bacterial spoilage. The current state of knowledge with respect to the diversity and activities of the spoilage microflora in these products is still limited. To date, studies on this subject are yet to be carried out in Finland. The aim of this study was to characterize the spoilage microorganisms found in ESL milks and pasteurised creams mainly produced in Finland. 10 ESL milks and 8 pasteurised cream packages were obtained from the Finnish retail market and were stored at 8?C, 15?C, room temperature and 30?C, respectively, until expiration. Total bacterial counts were evaluated and 31 bacterial isolates were selected. An attempt was made to characterize the bacterial isolates using rpoB and 16S rRNA partial gene sequence analyses. Psychrotrophic, spore-forming and spoilage features were also determined. Strain diversity was determined by rep-PCR profiling. Five selected isolates were subjected to metabolic profiling using the API50 CHB test. When growth was detected, total bacterial counts ranged from 2.67 to 3.74 and 2.54 to 8.98 log units in cream and ESL milk samples, respectively. Both ESL milks and cream samples were dominated by heat-resistant, spore-forming species of the Bacillus genera: the isolates were related to B. licheniformis. B. weihenstephanensis, B. safensis, B. kochii, B. pumilus, B. subtilis and B. anthracis. Intraspecies and intrasample strain diversity was very high. Isolates mainly displayed proteolytic and lipolytic activity. Psychrotrophic activity was high in the cream samples while most ESL milk isolates were mostly mesophilic. Tested isolates were non-lactose fermenters and had varying metabolic profiles. The study revealed that Finnish ESL milks and pasteurized creams are prone to spoilage by species of the Bacillus genera that have potential for lipolytic and proteolytic spoilage and some of which are considered toxigenic. There is wide intraspecies strain diversity responsible for the wide variability in metabolic, psychrotrophic and spoilage features. Phenotypic tests based on API50 CHB cannot be relied upon to make conclusions on taxonomy. Combining various methods is important for the comprehensive characterization of the bacterial isolates. Strategies to eliminate bacterial species of the Bacillus genera are important to prolong shelf life. However, intervention should be strain-specific to be effective. Large scale studies are required to confirm findings from this study.
  • Mulari, Harri (Helsingin yliopisto, 2020)
    Tämän tutkielman kirjallisuusosassa on selvitetty aiempien tutkimusten perusteella kaasutainnutuksen ja sähkötainnutuksen vaikutusta vertymien syntyyn, on myös tutkittu mm. aiheeseen liittyviä hyvinvointi asioita. Verenpurkauma syntyy verisuonten ylipaineen vuoksi lihakseen, ylipaineen tässä tapauksessa aiheuttaa tainnutus. Verenpurkaumat tainnutuksen yhteydessä aiheuttavat lihan laatuongelmia ja ovat eläimen kohtelukriteerinä ei toivottu ilmiö. Verenpurkaumia esiintyy enemmän sähkötainnutuksessa kuin kaasutainnutuksessa. Kaasutainnutus puolestaan on kyseenalaistettu useaan otteeseen tainnutusmenetelmänä eettisistä syistä, mutta teollisuus käyttää lähinnä CO2-tainnutusta sen nopeuden takia. Kokeellisessa osassa tutkittiin kahden erilaisen kaasutainnutusmenetelmän vaikutuksia vertymiin ja vertailtiin niitä. Samalla tutkittiin eri SEUROP-luokkien eroja sikojen vertymien esiintymiseen samalla aineistolla. Ruhon koostumuksella ja SEUROP-luokituksella on myös vaikutusta vertymiin aiemmin tehdyissä tutkimuksissa sähkötainnutuksessa, mutta kaasutainnutuksessa ei ole vastaavia tuloksia. Jalostustyön on arveltu olevan yhtenä selittävänä tekijänä, vähärasvaisuus ruhossa on korreloinut vertymiin. Verenpurkaumien esiintymiseen vaikuttavia tekijöitä joita kaasutainnutuksessa on mainittu aiemmissa tutkimuksissa mahdollisina syinä ovat stressi, väärä kohtelu, huono tilojen suunnittelu, jalostus, rotu, sukupuoli, pistoon kulunut aika ja tainnutus, joita ei voitu tässä tutkimuksessa sulkea pois. Kokeellisen tutkimuksen tulosten perusteella ei saatu tilastollisesti merkitsevää eroa hiilidioksidiryhmätainnutus- ja karusellitainnutussysteemin välille. Aikaisempien tutkimusten perusteella on huomattu, että on myös hankala kalibroida kaikki tekijät, jotka ovat mahdollisesti vaikuttavat vertymien syntymiseen.
  • Leinonen, Sara (Helsingin yliopisto, 2019)
    The literature part of the study reviewed the recommended gluten quantification method, immunological ELISA R5. R5 is a monoclonal antibody that recognizes mainly the epitope that is abundant in especially gluten protein subgroup, ω-gliadin. The current PWG-gliadin reference material used in ELISA leads to inaccuracy of the gluten content, because it cannot represent sample materials that differ in their gliadin composition. The aim of the experimental study was to compare the prolamin compositions of different wheat cultivars and their reactivity against R5 antibody in sandwich ELISA. The aim was to find the most suitable ratio of barley prolamin, C-hordein, to be used as a reference material for wheat gluten quantification. The ω-gliadin proportions of different cultivars were calculated from RP-HPLC-chromatograms. In order to compare the total wheat gluten reactivity of the cultivars in ELISA R5 with gliadin standard and C-hordein in different ratios (10, 20 and 30% in BSA), Km-values that measure the rate of sensitivity in the assay, were calculated. The method to separate gliadin- and glutenin subgroups in RP-HPLC was optimized (solvent to extract gliadin and glutenin, temperature, injection volume, gradient). For cv. Crusoe the ω-, α/β- and γ-gliadins and HMW- and LMW-glutenins were identified. The selected wheat cultivars were categorized into four groups. The proportion of ω-gliadin in total gliadin ranged from 0.8 to 14.1% between the cultivars, whereas for PWG-gliadin this has been reported to be 7.7%. In terms of similar reactivity (Km-value) in ELISA, 20% C-hordein was found to be the most suitable reference material (Km 90) for the selected wheat cultivars (Km average 92), instead of the current gliadin standard (Km 68). The advantage of C-hordein standard is that the concentration and thus reactivity can be adjusted to match the sample materials with different prolamin profiles. Unlike with current gliadin reference material, it can be used without any conversion factors, which improves the method accuracy.
  • Wu, Qimeng (Helsingin yliopisto, 2015)
    The literature review deals with water distribution in meat, the structure of the myofibrillar matrix, and the aspects related to the water-protein interaction. Special focus was given to the large water accessible area of myosin S1 units, surface hydrophobicity of proteins and factors affecting the hydrophobicity. Also the possible mechanisms of water-holding in meat were briefly introduced. The aim of the thesis was to study the effect of different ions and pH values on the surface hydrophobicity of the myosin S1 units, adding knowledge to the understanding of the interaction between myosin S1 units and water. Myosin S1 units were prepared from porcine longissimus dorsi muscle 48 h postmortem. Obtained myosin S1 units were subjected to 0.2 M, 0.4 M and 0.6 M ionic strength of NaCl and KCl and to pH 5.0, 5.5, 6.0, 6.5 and 7.0. The surface hydrophobicity of myosin S1 units was measured by fluorescent molecular probe (cis-Parinaric acid) method. The method of purifying myosin S1 units from porcine longissimus dorsi muscle 48 h postmortem was established under the conditions of our laboratory. Surface hydrophobicity was found to increase with increasing ionic strength of both KCl and NaCl. Concerning the different ions studied, only at 0.6 M, significantly higher surface hydrophobicity of myosin S1 units was measured in KCl compared to NaCl. This phenomenon is in accordance with chaotropic effect of K+ and Cl- and kosmotropic effect of Na+. Regarding the effect of pH, within KCl samples, more hydrophobicity myosin S1 unit was detected towards to the more acidic direction pH values than pH 6.0. For NaCl samples, at pH 5.5 and 6.0, surface hydrophobicity was significantly higher than at pH 5.0, 6.5 and 7.0. Differences may have been induced by the changes in the net charges of protein, and further in protein conformation. Considering the property of the protein surface, more hydrophobic protein results in less water-protein interaction. However, to look at the whole scenario of the interaction between myosin S1 units and water, changes of net charges of myosin S1 units and water structure at vicinity of them should be further studied.
  • Vainio, Matias (Helsingin yliopisto, 2020)
    The literature review of this thesis focuses on cooking loss and factors effecting it as well as low-temperature long-time (LTLT) cooking and how it effects meat. Reactions in meat during heating and their effects on meat products quality were also studied. The aim of the experimental research was to find the optimal strip size for one sous vide process to optimize cooking yield and sensory quality. To do so, pre-testing with several different strip sizes were performed and then one strip size was selected. With this strip size tests with 3 different meat types (chicken, pork and beef) were executed. The tests comprised 10 batches of around 100 kg of meat each type and both strip sizes totaling 60 batches with total weight around 7600 kg. The sensory evaluation was made with a panel of 15 workers from the company to determine if any changes occurred regarding the sensory quality. Every meat type was tasted and evaluated using a scale with a free line segment of 10 cm. The results were measured and the difference between the same type of samples were multiplied with 10 to achieve a difference measured in %-units. Every type of meat had higher cooking yield with larger strip size. Chicken improved the most, pork second and beef the least. The effects on sensory quality were moderate. Chicken and beef became less tender and pork improved, while juiciness of every type improved with bigger strip size. Chicken improved 31.9 %-units, pork 9.8 %-units and beef 6.7 %-units in cooking yield. Chicken overall acceptance seemed to have improved 0.3 %, pork 7.0 % and beef 1.7 % according the sensory evaluation.
  • Stamm, Matthias (Helsingin yliopisto, 2015)
    Microalgae (MA) are a novel feed ingredient for dairy cows. They are an alternative high quality protein source and rich in polyunsaturated fatty acids (PUFA). Supplementation of MA in dairy cow feeds has a potential to increase the amount of beneficial PUFA and bioactive molecules in milk. Four multiparous Finnish Ayrshire cows fed grass silage-based diets were used in a 4 × 4 Latin square with 21-d experimental periods to evaluate the effects of various protein supplements on fatty acid composition, oxidative stability, milk fat globule size and phospholipid content of milk. Dietary treatments consisted of 4 concentrate supplements containing soya (control), or one of three MA supplements: (i) Spirulina platensis, (ii) Chlorella vulgaris or (iii) Chlorella vulgaris + Nannochloropsis gaditana. Inclusion of MA in the diet decreased saturated fatty acid (SFA) content in milk compared to soya and tended to increase monounsaturated fatty acid and PUFA concentrations in milk. MA supplements increased 4:0, 5:0, 6:0, 17:0, 18:1 + trans-15 18:1, and 18:3n-3. Among algae, Chlorella vulgaris lead to highest contents of PUFA and 18:2n-6, Spirulina platensis to highest contents in 14:0, 16:0 and 18:3n-6 and Chlorella vulgaris + Nannochloropsis gaditana to highest contents of 6:0, 20:0 and 20:5n-3 in milk. Oxidation stability and phospholipid content of the milk were not affected by treatment. Diets containing Chlorella vulgaris led to a decrease in the number of milk fat globules, but mean globule diameter (d4,3) and milk fat globule size distribution in terms of volume were unaffected by treatment. Additionally, effects of individual animals on milk fat globule size distribution and phospholipid contents have been shown. In conclusion, MA supplementation moderately increased the content of PUFA at the expense of SFA compared to soya. Enrichment of specific fatty acids depended on the fatty acid composition of the supplement and stronger alterations of milk fatty acid composition will require higher contents of algal fatty acids. Premature spoilage through oxidation was not an issue. Finally, MA fed in the current study could only slightly alter the milk fat globule distribution, but phospholipid contents remained unchanged.
  • Viljanen, Janne (Helsingfors universitet, 2012)
    Exohomopolysaccharides (HOPS) are polysaccharides that are composed solely of glucose or fructose monomers and which are classified according to the linkage type between the monomers (e.g., dextran ?-[1?6]). Several different lactic acid bacteria (LAB) strains produce HOPS from sucrose. It is known that maltose can influence the synthesis of HOPS which can lead to formation of oligosaccharides. In fermented foods, HOPS and oligosaccharides can have both technological impact and prebiotic properties. The aim of this thesis was to investigate the synthesis of HOPS and oligosaccharides in mMRS broths and in oat bran gruel. Lactobacillus reuteri FUA 3048, Lb. reuteri LTH 5448, Weissella cibaria 10M and W. confusa DSM 20194 were used as starter cultures. HOPS and oligosaccharide yields in mMRS broths were analysed by ethanol precipitation and acid hydrolysis. An enzyme assisted method was used in order to quantify linear dextran content in freeze-dried oat gruels. Oligosaccharide profiles were analysed with high performance anion exchange chromatography with pulsed amperometric detetection. In mMRS broths, which contained 25 g/l sucrose (S-mMRS), LAB strains synthesised exosaccharides at concentrations of 0.9–2.3 g/l. Addition of maltose (34 g/l) significantly increased exosaccharide yield. This can be explained by strong malto-oligosaccharide (e.g., panose) synthesis. W. cibaria 10M produced 0.94 g/l linear dextran in S-mMRS broth and at 0.74 g/l in maltose containing broth and W. confusa DSM 20194 synthesised 1.7 g/l linear dextran in both broths. In oat gruel matrix (34 g/l maltose) W. confusa DSM 20194 synthesised 4.6 g/100 g dextran in freeze-dried gruel. In lower maltose concentrations dextran yield increased. Oligosaccharide profiles indicated that Weissella strains and the Lb. reuteri FUA 3048 strain synthesised gluco-oligosaccharides and Lb. reuteri LTH 5448 strain produced erlose. The results of this thesis give further insight in to role of maltose in HOPS synthesis in food matrices.
  • Penttinen, Elina (Helsingin yliopisto, 2017)
    Tutkielman kirjallisuuskatsauksessa perehdyttiin aromien herättämiin mielikuviin ja tunteita analysoiviin tutkimuksiin. Lisäksi selvitettiin, onko aromeilla vaikutusta stressiin tai työmuistiin, ja millaisilla menetelmillä niitä on tutkittu. Tutkimuksen tavoitteena oli selvittää, onko aistinvaraisella, verbaalisella kyselyllä ja valokuvilla mahdollista analysoida elintarvikearomien herättämiä mielikuvia ja tunnetiloja. Tutkimus tehtiin Fazerin kanssa yhteistyössä ja se koostui kahdesta kuluttajatutkimuksesta: aromitutkimuksesta (n = 116 henkilöä) ja viinikumimakeistutkimuksesta (n = 85 henkilöä). Aromeina käytettiin yksittäisiä elintarvikearomeja ja kahden elintarvikearomin sekoituksia. Ne valittiin sillä oletuksella, että osa herättäisi energisoivia (cola, inkivääri-appelsiini ja vesimeloni-greippi) ja osa rauhoittavia (vihreä tee, seljankukka-manteli ja hunaja-mansikka) assosiaatioita. Viinikumimakeistutkimuksessa näytemäärä vähennettiin neljään miellyttävimpään elintarvikearomiin: colaan, inkivääri-appelsiiniin, vesimeloni-greippiin ja hunaja-mansikkaan. Aromien herättämiä mielikuvia ja tunnetiloja tutkittiin kahden monivalintakyselyn (check-all-that-apply, CATA) avulla. Aluksi arvioijat valitsivat 16 energisoivaa ja rauhoittavaa assosiaatiota herättävästä valokuvasta jokaista aromia/makua kuvaavat valokuvat. Seuraavaksi arvioija valitsi 25 sanan aromitutkimuksiin suunnatusta tunnetermistöstä (Universal Emotion and Odor Scale, UniGEOS) kutakin tutkittua aromia/makua kuvaavat sanat. Lisäksi näytteiden miellyttävyys ja tuttuus määritettiin 9-portaisella luokka-asteikolla. Tutkimuksissa tuttuus ja miellyttävyys korreloivat ja aromit arvioitiin keskimäärin miellyttävämmiksi kuin vastaavia aromeita sisältäneet viinikumimakeiset. Aromien herättämille mielikuville valitut kuvat asettuivat suurimmaksi osaksi juuri energisoivien ja rauhoittavien valokuvien kohdalle, poikkeuksena hunaja-mansikka. Molempien tutkimusten kohdalla ennakko-oletukset täyttyivät inkivääri-appelsiinin ja colan tunnetermien arvioinnissa, sillä ne arvioitiin virkistäviksi ja energisoiviksi. Tuloksemme osoittavat, että monivalintakyselyn verbaaliset ja visuaaliset menetelmät ovat kuluttajatutkimuksissa hyödyllisiä aromien mielikuvien ja tunteiden analysoimiseen.
  • Johansson, Ari (Helsingin yliopisto, 2015)
    Emakonlihaa käytetään kestomakkaran valmistuksessa ympäri maailmaa (Pidcock ym. 2002; Rason ym. 2007). Emakonlihan käyttö ei ole kuitenkaan vakiintunut kestomakkaroiden lihalajitelmien lähteeksi Suomessa. Suuri syy tähän ovat emakonlihaan liittyvät ennakkoluulot, sillä. emakonliha poikkeaa väriltään ja aromiltaan lihasian lihasta (Sindelar ym. 2003). Vingolon ym. (2010) mukaan lihalajitelmien voimakkaan punainen väri on kestomakkaroissa haluttu ominaisuus, mikä voisi tukea myös emakonlihan käyttöä kestomakkaroiden raaka-aineena Suomessa. Kestomakkaroissa on valmistustavasta riippuen usein voimakkaan savuinen sekä suolainen aromi, joka saattaa peittää emakonlihalle tyypillisen metallisen ja happaman maun. Calkins ja Hodgens (2007) havaitsivat, että myoglobiinin määrän kasvu aiheuttaa naudanlihaan metallisen maun. Myoglobiini on lihan tärkein väripigmentti, ja sitä on emakonlihassa enemmän kuin lihasian lihassa (Bader 1983). Tutkielman kokeellinen osuus jakaantui kahteen osioon: ensimmäisessä osiossa verrattiin lihasian ja emakon M. longissimus dorsia keskenään laboratorio-olosuhteissa. Toisessa osiossa valmistettiin kestomakkaroita, joiden emakonlihapitoisuus vaihteli. Kestomakkaroiden kypsytystä seurattiin kolmen viikon ajan (pH-arvo, kosteus, kiinteys ja veden aktiivisuus). Valmiille kestomakkaroille tehtiin myös aistivaraiset arvioinnit, joissa kestomakkaroiden väriä, kiinteyttä ja aromia verrattiin keskenään. Kypsymisen seuraamisesta pystyttiin havaitsemaan, että osa kestomakkaroista poikkesi tilastollisesti merkitsevästi (p < 0,05) pH-arvoltaan ja kiinteydeltään kypsytyksen aikana. Aistinvaraisen arvioinnin tuloksista pystyttiin havaitsemaan, että kestomakkarat poikkesivat toisistaan tilastollisesti merkitsevästi värin osalta (p < 0,05), mutta kiinteyden ja aromin osalta eivät. Tutkimuksen tulosten ja kirjallisuuskatsauksen perusteella voidaan todeta emakonlihan sopivan kestomakkaroiden raaka-aineeksi
  • Suvanto, Sonja (Helsingfors universitet, 2017)
    The literature review focused on the characteristics of bread-quality rye and how the composition and functional properties of rye are influenced by genotype and environment. Traditional rye sourdough baking process and main baking quality measurements were reviewed. The aim of this work was to identify baking quality of rye flour with different falling numbers. Another aim was to identify the measurement that best determines the quality of rye flour for sourdough baking and to find enzymes that can be used to improve poor-quality flour. In the experimental study, the baking quality of rye flours with different falling numbers (100, 130, 200, 300) was examined in processes for making sourdough rye loaves and serving-size flat breads. Rye flours with high falling numbers (200 and 300) were treated with commercial amylase and xylanase preparations. Falling number, amylograph and swelling curve measurements were done and results were compared to quality obtained in baking trials. Rye flour with the highest falling number (300) resulted in hard and dry dough as well as dense bread, as expected. Other rye flours (100, 130, 200) and flours treated with amylase resulted also in rather hard and dry doughs, although falling number and amylograph measurements confirmed the enzyme activity. Lower falling number and amylase treatments, however, were associated with improved sensory quality of final products. Xylanase made doughs softer and stickier, which improved both handling properties of dough and quality of bread in the loaf process. In contrast, the increased softness and stickiness made the serving-size flat-bread process more difficult. The viscosity decrease caused by xylanase addition was seen in swelling curve measurements. Adjusting the acidity of buffer solution to the pH level of rye sourdough did not improve the ability of the swelling curve to predict the baking behaviour of the flour. This study showed that falling number and amylograph cannot predict properties of rye dough. Differences between rye flours with different falling numbers were best detected in the sensory quality of the final products. The baking quality of rye flours could be modified by enzyme treatments, especially by xylanase addition, but the usefulness and desirability of the treatment depended on the type of bread-making process. The effects of added xylanase in rye dough could be predicted by swelling curve measurement. The overall results emphasized the importance of baking trials in determining the baking quality of rye flour.