Browsing by Subject "Elintarviketeknologia (yleinen elintarviketeknologia)"

Sort by: Order: Results:

Now showing items 1-12 of 12
  • 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.
  • Pulkkinen, Jukka (Helsingfors universitet, 2011)
    Emulsified films are prepared by drying an emulsion. Polysaccharide based emulsified films consist of film-forming polysaccharide, fat, emulsifier and plasticiser. In the literature review, the materials used in the preparation of polysaccharide based emulsified films were discussed. The review also included a discussion of which factors affect the water barrier and mechanical properties of the emulsified films. The aim of the experimental study was to find out the potential of konjac glucomannan (KGM) and galactoglucomannan (GGM) in emulsified films. The effect of fat type and fat content on the water barrier and mechanical properties of the films were studied. Emulsified films which contained 30% (wt-% of GGM) fat were prepared from beeswax, rapeseed oil and pine wood oil. Fat contents of 10 and 50% were also used for beeswax. Emulsified films were compared with control films that did not contain any fat. The ratio of KGM and GGM used was 1:1. The water vapour permeability (WVP), water vapour transmission rate (WVTR), Young’s modulus, tensile strength and elongation at break were measured. Films were also viewed with a scanning electron microscope (SEM). KGM and GGM were suitable materials for emulsified films. The surfaces of films dried at room temperature were more uniform than those dried at 60 °C. In the SEM images, wax droplets were smaller than oil droplets. The diameter of oil droplets was about 10 ?m and 2–6 ?m for wax droplets. Wax droplets were better entrapped in the film matrix probably due to their smaller size. As expected, best water barrier properties were obtained with films containing 50% beeswax (p < 0.05). WVP of the films decreased when the content of beeswax in the film increased. Films containing 30% oils and 10% beeswax did not differ significantly from the control film in water barrier and in mechanical properties. The lowest Young’s modulus was with 50% beeswax film. The control film was the stiffest and strongest. There were no statistically significant differences in elongation at break between the films. Emulsified films were successfully prepared from KGM and GGM. The water barrier properties of emulsified films were better than those of the control film and still the mechanical properties were rather well maintained.
  • Järvelä, Anu (Helsingfors universitet, 2011)
    The fish processing industry requires a method by which shelf life of whitefish could be reliably assessed in real time. Quality Index Method (QIM®) has been used in several European countries for many different species of fish. QIM® predicts the remaining shelf life of fish species based on changes in sensory characteristics. The aim of the present study was to create the QIM® for sea-farmed whitefish, the first QIM® for Finnish fish, which could be included in the official QIM® folder. The study was conducted in the Finnish Food Safety Authorty (Evira). Examined fishes were purchased from Kalatukku E. Eriksson Ltd. pH value and a microbiological method were used to evaluate shelf life. Sensory profiles were created (n = 13). Two profile panels (n = 9) and the QIM® panel (n = 5) evaluated the raw and cooked fish. The result was also ensured by quality scoring for fish (Evira 8001). The QIM® panel created a draft for the QIM® frame, and the draft was further tested. Photos of fresh fish samples were taken. The QIM® draft created according to this study was an effective basis for initiating the validation of the QIM® prepared. It can also be noted that the QIM® itself was suitable for sea-farmed whitefish. Cooked fish analysed with a sensory evaluation method (Evira 8001), and found the time when you can find spoiled taste of from cooked fish and the examination of raw fish can be stopped. The microbiological method “Determination of the number of microbes” (Evira 3420/1) correlated with the QIM® result, fish samples were polluted on the fifteenth day. The pH results did not provide reliable results with which the QIM® result could have been compared. The prepared QIM® created for the sea-farmed whitefish could be utilised in the future in the Finnish fishing industry. It would be useful if QIM® was created for the other most common Finnish trade fish, so that the expiry dates on packages would be based on one common method, and thus the last day of use would have a scientific basis.
  • Mononen, Riikka (Helsingfors universitet, 2012)
    The literature review deals with sensory properties of apples, factors affecting consumer perception and apple acceptability and methods that can be used to study these phenomena. Apple cultivation and consumption in Finland and demands set by legislation were also examined. The aim of the experimental work was firstly to produce sensory profiles for eight domestic winter apple varieties (Amorosa, Aroma, Eva-Lotta, Konsta, Lobo, Red Atlas, Valtti and Åkerö Hassel), secondly to study consumers’ apple perception using a home-use-test and finally to use preference mapping to combine data from descriptive analysis and consumer test. Apples were evaluated at two different time points in order to study how ripening affects sensory properties and consumer perception. The panel in descriptive analysis consisted of 11 trained assessors. Participants of the consumer test (n=80) were mainly students and staff of the University of Helsinki. Eva-Lotta, Amorosa and Aroma had the sweetest flavour. Valtti and Red Atlas had the most acidic and astringent flavour with the highest flavour intensity. Lobo, Red Atlas and Konsta had the mealiest texture and ripening caused severe deterioration in texture for these three varieties. Aroma and Valtti had the crispiest texture while Lobo had the lowest texture crispiness. Eva-Lotta and Valtti were the juiciest varieties and had the highest scores in fruity aroma. Statistically significant differences between varieties were found in all other attributes except soggy texture and grassy aroma. Eva-Lotta was the most preferred variety. Eva-Lotta, Amorosa and Aroma had the most pleasant taste while Red Atlas and Åkerö Hassel had the least preferred taste. Strong correlation between overall liking and taste pleasantness was observed. Willingness-to-buy was mostly explained by overall liking. No explicit consumer groups were identified using cluster analysis which was probably due to homogeneity of the participants. Most of the participants preferred sweet and fruity apples although some exceptions were observed.
  • Palmujoki, Ingela (Helsingfors universitet, 2013)
    The literature review focused on the history, present and future challenges of the Finnish school meal. According to earlier studies most of the students eat the school lunch, however only one third of them eat all components that are part of the meal. The aim of this work was to investigate background- and contextual factors affecting acceptance of school meals. A total of 147 students from two schools in Helsinki participated in the study. They were third graders (n=43; 20 girls, 23 boys), sixth graders (n=54, 28 girls, 26 boys), and eight or nine graders (n=31; 17 girls, 14 boys). The participants evaluated 13 school meals and 26 main dishes (13 basic dishes and 13 vegetarian dishes). The main dishes differed due to different dish types and main ingredients. The participants evaluated the meals and the dining situation on questionnaires, in a class room, after the lunch break. A photo of the meal of the day was projected on a screen to remind them of the experience. The respondents checked the immediate emotion when seeing the meal, liking of the meal and its components, the appropriateness of saltiness, spiciness and temperature of the main dish and the dining situation. Demographic data, attitude to school meals in general, food neophobia score, and ratings as response to food names of 30 school meals were collected separately. Liking of the meals and meal components were affected by the age and food neophobia score of the participant. The third graders scored higher for most main dishes and meal components than the sixth graders. Participants with a lower food neophobia score liked the meals better than participants with high scores. 35 % of the overall acceptance of school meals was explained by attitude towards school meals in general, the temperature of the main dish, the participants hunger state before lunch, the saltiness of the main dish, food neophobia and the temperature of the drink in a stepwise regression model. Hunger state was the most explanative factor for the third graders, while the sixth graders acceptance to school meals was mainly explained by the attitude towards school meals in general. The results of this study indicate that the attitude towards school meals get more negative with age. Hence, identifying the factors underlying this attitude change is important in order for the school meal to be accepted and eaten also by older students.
  • Mustanoja, Ella (Helsingfors universitet, 2014)
    The literature review was concerned with colourful vegetables and the most common pigments in vegetables: carotenoids, anthocyanins, betalaines and chlorophyll. In addition, how thermal treatments affect these pigments and the structure of vegetable was reviewed. The aim of the experimental work was to investigate the effect of thermal treatments on the colour, pigments and texture of carrots and beet-roots. Seven coloured carrot cultivars and four coloured beet-root cultivars were examined. Three different kinds of thermal treatments were applied to the samples: blanching, boiling and steaming. Orange and purple carrots contained the highest amounts of carotenoids. The total carotenoid content of the carrots increased due to the thermal treatments. Purple carrots were the only carrots which contained anthocyanins. Anthocyanin stability is pH dependent: boiling in slightly acidic water had a minor impact on anthocyanin content than boiling in pure water. Red beet was the most betalain-rich beet-root. Other cultivars contained remarkably less betalaines. Betalain content decreased due to the thermal treatments. Betalain degradation due to the thermal treatments was detected as the pigment content and colour changed. Thermal treatments softened the vegetable structure. Thermal treatment improves the extraction of the pigments from the vegetable structure, which was detected as the increase in pigment concentration, leading to an enhancement of bioavailability of pigments. However, long thermal treatments cause pigment degradation and reduce the nutritional value of the vegetables.
  • Mikkonen, Tiia (Helsingfors universitet, 2012)
    The literature review dealed with composition of lingonberry, effects of processing on phenolic compounds and spray drying juices with the help of carrier agents. The aim of the experimental work was to spray dry lingonberry juice with the help of carrier agents, examine the properties of juice powders and explore how juice powders suit for selected applications. The total content of phenolic compounds was also measured from the lingonberry juice and powders. Maltodextrin DE 5–8 (MD), whey protein isolate (WPI) and combination of carrier agents (MD+WPI) were used as carrier agents while yield, glass transition temperature, colour, solubility and total content of phenolic compounds were the properties examined. A milk based lingonberry smoothie, lingonberry marmalade, lingonberry marshmallow and lingonberry spread were developed as applications. The spray drying of the lingonberry juice and subsequent applications were successful. The highest yield (20.9%) was achieved when MD was used as a carrier agent. WPI had the lowest yield (9.8%). MD-juice powders had the highest glass transition temperature at all relative humidities used (0, 11, 24, 33 and 44%) and WPI-juice powder had the lowest. Commercial juice powder had the darkest colour (garnet) and MD+WPI-juice powder was the lightest (light pink). MD-juice powder had the poorest solubility and commercial powder had the best, although MD was a carrier agent in both. The total content of phenolic compounds in lingonberry juice was 246.4 mg/100 g and in the best juice powder (WPI) 3.6 mg/100 g. Juice powders had differences in colour when used in applications and smoothies also had differences in stability of foam. MD and commercial powder formed a stabile foam structure but WPI-smoothies separated into liquid and foam phases. Lingonberry juice powders did not affect the structure of marmalades or marshmallows. In lingonberry spreads commercial juice powder blended the best into margarine. Lingonberry juice powders are interesting products. Lingonberry juice powders would suit well in different applications to add colour and taste. Due to low glass transition temperature, powders were difficult to handle. With some further research this stickiness problem could be solved.
  • Alakalhunmaa, Suvi (Helsingfors universitet, 2014)
    Aerogels are lightweight, porous and dry foams that are produced from gels by replacing the liquid phase by air. When produced from polysaccharide-based hydrogels, potential applications for aerogels could be found as bio-based packaging materials. The literature review focused on the production of polysaccharide-based hydrogels and their chemical crosslinking, as well as the production of aerogels and their properties. In the experimental study the possibilities for utilization of spruce galactoglucomannan (GGM), an abundant but largely unexploited raw material, as aerogel matrix was explored. Nanofibrillated cellulose (NFC) was used as reinforcement and the polysaccharides were crosslinked with ammonium zirconium carbonate (AZC). Hydrogels were prepared from GGM-NFC-suspensions and heat treatment was performed in order to induce crosslinking reaction. Prepared hydrogels were frozen in a bath of carbon dioxide ice and ethanol and subsequently freeze-dried into cubic aerogels. The aim was to investigate the effect of polysaccharide proportions and AZC content on the strength of hydrogels and on the mechanical properties and moisture sensitivity of aerogels. The formation of crosslinks was observed indirectly from the values of storage and loss moduli by dynamic rheological measurement. The strength of hydrogels was highly dependent on the AZC and NFC content. In contrast, the compressive modulus of aerogels instead was affected only by NFC content at relative humidity (RH) of 50% and 23 °C. Hydrogel strength could not be used for prediction of aerogel strength under these ambient conditions. AZC and NFC mainly decreased the sensitivity of aerogels towards moisture by decreasing the water absorption and its plasticizing effect on aerogels. The effect of crosslinking on mechanical and physical properties of aerogels appeared clearly at RH over 50%. GGM was shown to be a suitable aero-gel raw material when combined with NFC. The role of NFC in enhancing the aerogel’s me-chanical properties was significant. The mechanical properties of uncrosslinked aerogels, how-ever, weakened in a humid environment. In particular, AZC is needed to protect aerogels from the plastizicing effect of water. Properties of crosslinked aerogels in a humid environment would be an interesting subject of further studies.
  • Viksten, Suvi (Helsingfors universitet, 2012)
    The literature review focused on the proteins and insoluble fibre, ?-(1->4)-galactan, of blue lupin seed and how they degrade during germination. The review also dealt with the food applications of lupins and the harmful substances of lupins: allergens and ?-galactosides. The object of the experimental study was to determine the peptidase activities in the blue lupin seeds at the different stages of germination, classify the peptidases in the seeds and investigate the changes occuring in the proteins during germination and fermentation. The percentage of the water-soluble protein in the seeds was also determined. Blue lupin seeds were soaked in water over night and were germinated in the dark (15 ° C, RH 100 %). Peptidase activities were determined spectrofotometrically using azo-casein as a substrate. Class-specific peptidase-inhibitors (Pepstatin A, PMSF, E-64 and O-FEN) were used for classification of peptidases. Lactobacillus brevis and Lactobacillus rhamnosus were used in the fermentations (35 °C, 24 h) as well as baking yeast. The changes which occured in the proteins during germination and fermentation were investigated by electrophoresis (SDS-PAGE). The Dumas method was used to determine the percentage of the water-soluble protein in the extracts composed of soaked and germinated (2 day) seeds. Peptidase activities increased until the second day of germination and then remained constant until the fourth day. Serine- and aspartic peptidases were identified by inhibitor tests but not cysteine peptidases, even though cysteine peptidases have been previously known to break down legume proteins during germination. The cysteine peptidase inhibitor, E-64, used in this study has been observed earlier to inhibit cysteine peptidases belonging to papain family but not to legumain family. Proteins degraded slightly when the germination continued 4 days, and the degradation continued further during the fermentations. Large polypeptides (MW 45–100 kDa) mainly degraded during germination and fermentation. In addition, 17 kDa polypeptides degraded during fermentation. Possible 20 kDa hydrolysis products also formed during fermentation. The degradation of proteins in fermentations was more efficient when seeds germinated for 2 days were used compared to ungerminated seeds. The content of the water-soluble protein in the soaked seeds and the seeds germinated for 2 days varied between 35–96 %, and the content increased markedly when the pH of the extraction solvent increased from 6 to between 7.5–9.0. Thus the alkalinity of the extraction solution changed the structure of the storage seed proteins to more water-soluble form. The peptidase activity of germinated blue lupin could be applied in varied fermentation processes. The storage proteins of blue lupin were extremely water-soluble, so this discovery could be utilised for manufacturing substitutes for dairy products.
  • Suihkonen, Terhi (Helsingfors universitet, 2013)
    The literature review dealed with the composition of lingonberry, manufacture of juice powder and the effects of different carriers on properties of juice powder, especially glass transition temperature and stickiness. In addition, physical, functional and nutritional properties and the effect of storage conditions on juice powders were covered. The aim of the experimental work was to investigate the effect of spray- and freeze-drying and carriers on glass transition temperature and water sorption of lingonberry juice as well as the stability of vitamin C and phenolic compounds during drying and storage. The same amounts of maltodextrin (MD), whey protein isolate (WPI) or combination of MD/WPI in equal proportions were added to each sample. All samples were spray- and freeze-dried. After storage of powders at different relative humidities, glass transition temperature, water sorption, content of L-ascorbic acid and content of phenolic compounds were examined. Water sorption was examined by static and dynamic vapour sorption methods. The small particle size of containing WPI was problematic with spray-drying because not all of the powder in the drying air could be separated in the cyclone. Adding water back into the spray-dried samples was most difficult when the samples were stored at low relative humidities (0–11%). The smallest water sorption was observed with both static and dynamic vapour sorption methods in samples which contained only MD. Water contents of freeze-dried samples were lower than those of spray-dried samples. BET sorption isotherm described the water sorption behaviour of the lingonberry juice powders well. Glass transition temperatures of all samples decreased as the relative humidity increased. During storage, the amount of phenolic compounds in samples containing WPI remained the same, whereas the amount of phenolic compounds in samples with MD decreased. Enzymatic spectrophotometric determination was un suitable for determing L-ascorbic acid in lingonberry powder because the sample colour disturbed the measurement. MD and the combination of MD and WPI were suitable carriers in lingonberry juice. The amount of phenolic compounds in lingonberry juice powders were preserved well by whey protein isolate. Therefore, the spray-drying process should be developed in a way that brings about increase in particle size of powder containing WPI.
  • Ishchenko, Tatiana (Helsingfors universitet, 2014)
    Propionibacterium freudenreichii is commonly known as a Swiss-type cheese ripening culture, and is also frequently applied in the industrial production of vitamin B12 (cobalamin). One way to increase vitamin B12 productivity is the supplementation of medium with 5,6-dimethylbenzimidazole (DMBI), the lower ligand of cobalamin. The aim of this thesis was to investigate the effect of exogenous DMBI on vitamin B12 synthesis and protein production in type strain of P. freudenreichii ssp. freudenreichii. Results showed that DMBI supplementation improved cobalamin production 2.7- and 2.0-fold in cultures grown in anaerobic and two-step processes, respectively. Two-step incubation enabled the achievement of significantly higher levels of cobalamin both in the absence and presence of DMBI. The highest cobalamin level of 0.6 ?g/ml was achieved by the combination of DMBI supplementation with the two-step process. Proteome maps displayed 474 protein spots which is less than 20% of P. freudenreichii predicted proteome. No significant differences in protein production were found between cultures grown in the absence and presence of DMBI. Only two protein spots were more abundant in presence of DMBI and four spots showed higher abundance in absence of DMBI. None of detected proteins from these spots were found to be directly involved in cobalamin biosynthesis.
  • Österman, Erika (Helsingfors universitet, 2012)
    The literature review deals with baking tests and rheological measuring devices, which measure the baking quality of wheat flour. The farinograph measures, for example, the water absorption, the alveograph the gas retention capacity, the extensograph the extensibility and the amylograph the starch gelatinisation of the sample. Chopins’ Mixolab-device imitates the whole bread-baking process by measuring water absorption, mixing tolerance, gluten quality, starch gelatinisation, starch gel stability and starch retrogradation of the sample. The aim of the experimental work was to determine the applicability of the Mixolab-device to measure the baking quality of wheat flour and to find out whether the results obtained by Mixolab correlate to the results of baking tests. The repeatability of the Mixolab results was ensured by repeating measurements five times. Seven gluten preparations (2% of the wheat flour mass), three enzyme preparations (30 and 70 ppm of the flour mass) and bread improvers (0.5–2.0% of the flour mass) were analyzed in wheat flour with Mixolab to find out how they affect the baking quality of wheat flour. Two gluten preparations which differed most from each other and all enzymes with both concentrations and reference sample were test baked. According to the results obtained using Mixolab, one of the gluten preparations differed from others by making the sample softer and having bigger volume than all the other gluten preparations, which made samples harder, have a smaller volume and larger water absorption potential. The exceptional gluten preparation and one of the other gluten preparations were test baked. The results obtained using Mixolab were confirmed by baking tests: samples including the exceptional gluten preparation were softer and had a greate volume than the sample which included the other gluten preparation. One enzyme preparation softened the dough more and had a bigger volume than the others. Test baking showed that the enzyme preparation possessed proteolytic activity, and destroyed the gluten matrix of the dough. The other two enzymes were quite similar and the bigger concentration softened the dough compared to the reference sample. Mixolab showed also clear differences between the bread improvers. The results obtained using Mixolab were repeatable, differences were found between samples and the results correlated with the results of the baking tests. It was difficult to interpret the results of Mixolab and that is why test baking was compulsory. There is still a lot to learn about interpreting the results of Mixolab and test baking can’t be replaced by Mixolab, at least not yet.