Browsing by discipline "Livsmedelsteknologi (allmän livsmedelsteknologi)"

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.

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.

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.

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.

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.

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.