Browsing by discipline "Food Science"

To acquire sufficient amount of vitamin B12 (2-3 ?g/day), humans mostly consume animalderived foods in their diet, making vegetarians and vegans highly susceptible to vitamin B12.deficiency. Although sufficient vitamin B12 intake can also be met by consuming fortified foods and vitamin B12 supplements, there is an increasing trend to consume natural and food grade products rather than supplements in tablet form. However, plant-based fermented foods that contain naturally synthesized vitamin B12 are limited. This study therefore aimed to investigate the requirement of different precursors in the biosynthesis of vitamin B12 in optimal media conditions and then in cereal matrices using strains of Propionibacterium freudenreichii. Vitamin B12 was produced by three selected P. freudenreichii strains (strain 1, 2 and 3) in supplemented whey permeate (SWP) medium, 30% w/v barley malt matrix and 6% barley flour matrix. The additions of 5 mg/L cobalt chloride, 15 mg/L DMBI, 15.05 mg/L riboflavin and 3.29 g/L nicotinamide were investigated. The effects of three different time points (0, 72, 144 h) in adding riboflavin and nicotinamide were also investigated. Depending on the type of precursors and the timing of adding the precursors, six conditions were tested in the SWP medium, while three conditions were tested in the cereal matrices. After extraction in the presence of sodium cyanide, vitamin B12 was then quantified by microbiological assay (MBA) and ultra high-performance liquid chromatography (UHPLC). The two-stage fermentation of 72-hour anaerobic/96-hour aerobic fermentation led to high vitamin B12 yields with maximum production of 2.20 ?g/mL and 1.41 ?g/g produced in the SWP medium and the barley malt matrix, respectively. Depending on the type of precursors added in the culture samples, the capacity of the P. freudenreichii strains in vitamin B12 production varied. The strain 3 produced maximum vitamin B12 yields with the addition of riboflavin and nicotinamide at 0 h. With the vitamin B12 amount achieved in the fermented cereal matrices, this study successfully demonstrated the promising possibilities to enrich plantbased foods with vitamin B12 through in situ fermentation.

Faba bean flour is a sustainable and relatively inexpensive way to make protein rich food in comparison with meat products, because it has high proteins content (rich in lysine (30%)) and considerable amounts of vitamins, minerals and dietary fibre. Even rough faba bean is widely cultivated and consumed, few data is available concerning the suitability to be fermented. The objective of this master’s thesis was to study the potential of sourdough fermentation of faba bean with selected lactic acid bacteria for in situ production of dextrans as texture forming components for various food applications. In this study, the growth and dextran formation by Leuconostoc and Weissella in faba bean sourdoughs were investigated. Eight lactic acid bacteria belonging to genera Leuconostoc and Weissella characterized for slime formation were used as starters for in situ formation of exopolysaccharides in faba bean flour. The growth of lactic acid bacteria, pH and acidity, and viscosity of different sourdoughs were analyzed. An enzyme assisted method and acid hydrolysis were used to analyze dextran content with further quantification by HPAEC-PAD. The amount of dextran formed by Leuc. pseudomesenteroides DSM 20193, Leuc. mesenteroides subsp mesenteroides LMG 7939, Leuc. Citreum DSM 5577, W. cibaria LMG 17699, and W. cibaria Sj1b varied from 1.86 to 4.22 g kg-1 (wet weight), which allows the possibilities to use dextran as alternatives for hydrocolloids in food applications. The synthesized dextran increased significantly viscosity of sourdoughs. After fermentation, the amount of raffinose family oligosaccharides (RFO) were decreased. The results of the sourdough fermented faba bean flours showed that Leuc. pseudomesenteroides DSM 20193 and Leuc. Mesenteroides subsp mesenteroides LMG 7939 were the most potential strains to produce dextrans and increase viscosity properties.

Bacteriocins are ribosomally synthesized antimicrobial proteins. They can be applied as biopreservatives in food processing for extending the shelf-life of food. Lactic acid bacterium Leuconostoc carnosum 4010 is Generally Recognized As Safe strain, which can be used as a protective culture in meat products. The strain 4010 produces three bacteriocins: leucocins A (LcnA), B (LebB) and C (LecC). For the secretion of bacteriocin out from the cell, bacteria usually use an ABC transporter, which is often dedicated to secrete only one bacteriocin. The leucocin operons in Ln. carnosum 4010 plasmids include genes for only one ABC transporter, namely LecXTS. The fact that Ln. carnosum 4010 produces three bacteriocins but only carries one bacteriocin transporter, raises a question, which leucocin(s) is/are translocated via LecXTS transporter. Therefore, the first aim of this study was to determine which bacteriocin(s) is/are secreted by LecXTS in Ln. carnosum 4010. Ln. carnosum 4010 carries at least two plasmids. Leucocin A gene lcnA is located on the plasmid pLC4010-2, and leucocin B and C with transporter genes (lebB, lecC, lecXTS) are located on the plasmid pLC4010-1. In a previous work, two plasmid cured derivatives of Ln. carnosum 4010 have been made: the plasmid-free strain PCS-10, and the strain PCS-11 carrying only pLC4010-2. Neither of the derivatives secrete bacteriocins. In this study, the idea was to construct five recombinant plasmids containing the pLC4010-1 replication gene repB and a gene for erythromycin resistance ErmR. They were ligated with different sets of leucocin and transporter genes (repB-lebB-lecXTS-lecC-ErmR, repB-lebB-lecXTS-ErmR, repB-lebB-ErmR, repB-lecC-ErmR, and a vector control with only repB-ErmR). The constructs were aimed to be introduced into the two Ln. carnosum 4010 mutant strains PCS-10 and PCS-11. However, after several attempts of electroporation, no colonies were obtained. To acquire a testing plasmid for optimization of transformation, the ligation mixture for the smallest plasmid repB-ErmR was electroporated into another strain, Lactococcus lactis N8. The plasmid repB-ErmR was successfully obtained from Lc. lactis N8. For improving the efficiency of transformation, the plasmid repB-ErmR was isolated from Lc. lactis N8, and the plasmid was used in optimization of electroporation. The copy number of the plasmid was shown to be very low, as only a little amount of plasmid could be isolated from large culture volume. Even with optimized electroporation method, the repB-ErmR could not be electroporated into Ln. carnosum 4010. This indicates that the larger constructions are nearly impossible to be transferred into the strain Ln. carnosum 4010. In conclusion, it was confirmed that the plasmid replication gene repB of Ln. carnosum 4010 is functional in Lc. lactis. Due to the low copy number of the plasmid repB-ErmR, the amount of plasmid was definitely a problem in electroporation. Therefore, for studying the efficiency of electroporation, the plasmid amount needs to be increased. Although the electroporation of repB-ErmR into Lc. lactis was successful, the results from Ln. carnosum electroporation after optimization indicate that the strain Ln. carnosum 4010 is difficult to be transformed.

Literature review of the thesis introduces the characteristics of selenium and its importance in human diet. It also gives an overview on different analytical methods used in speciation of selenoamino acids. The aim of this study was to develop a simple and rapid mass spectrometric method which could be used to detect and specify low molecular weight selenoamino acids from different food materials in order to find and quantify probable cancer protective species. Total selenium content was determined by GFAAS from garlic and Brazil nut samples. The selenium concentration in garlic was 0.1 µg/g and 4.4 µg/g in Brazil nuts. Also, the precipitates and supernatants from the sample extractions (hot water, diluted HCl and proteinase K) were analyzed. There were only about 10% of the total selenium in the supernatants (which were further used in analysis). Samples were derivatized by AccQ·Tag reagent (AQC) and analyzed with UHPLC-ESI-MS method. Even though the method was easy and fast to use, it was applicable only for selenoamino acid standards (MeSeCys and SeMet). No results were obtained from the real samples. Therefore, a more sensitive piece of equipment, HPLC-ICP-MS was applied with Hamilton PRP-X100 column and 5 mmol/l ammonium citrate buffer (pH 5.2). Hot water and diluted HCl extracted samples showed no signs of selenium. At last, proteinase K digested Brazil nut sample showed a small peak of SeMet which was identified by retention time matching with the standard and quantified semi quantitatively from standard curve (0,06 µg SeMet /g Brazil nut). This study showed that the sensitivity of the UHPLC-ESI-MS method was not sufficient to detect such low concentrations of selenoamino acids in garlic and Brazil nut samples. However, the AQC derivatization together with UHPLC-ESI-MS offers a fast, linear and repeatable method for future amino acid analysis.

The literature review deals with the basics of microalgae, microalgal cultivation and harvest, and the organism Euglena gracilis. The carbohydrates found in E. gracilis are discussed, with the focus on the storage carbohydrate paramylon. The review also deals with effects of cultivation conditions on composition of microalgae. The aim of the experimental work was to investigate carbohydrate composition in E. gracilis, and in this way increase the knowledge of the microalgae. E. gracilis cultivated in five different environments was studied for content of the beta-glucan paramylon, as well as free sugars and oligosaccharides. As the method used for determination of paramylon content was a gravimetric method, a glucose measurement, protein determination and size-exclusion chromatography were performed on the paramylon isolated. In addition, the effect of supercritical fluid extraction (SFE) of the biomass to extract high value compounds on the overall carbohydrate composition and content was also investigated. In addition, the SFE samples were also analysed according to the AOAC method for dietary fibre The paramylon content in the E. gracilis biomass was between 22 and 40 % of the dry biomass. SEC analysis of this paramylon isolated showed that it was of molecular weight around 150 kDa, but that it was not only paramylon that had been isolated, but the isolates also contained impurities. This was also confirmed by the analysis of glucose and protein in the isolates. Possible compounds that can have been isolated with the paramylon are leftover peptides bound to the tight paramylon structure, chlorophyll, or glycoproteins. The most abundant sugars found in E. gracilis biomass were mannitol, trehalose and glucose, with a total content of and the total content of the samples were from between 2.4 and 14.9 % of the E. gracilis of the total dry mass. There were also some other unquantified free sugars, such as lactose seen in the E. gracilis biomass. The oligosaccharide content was considered low and not further quantified.

To study the feasibility of replacing dairy proteins with plant proteins to stabilise emulsions, 9 emulsions were prepared at pH= 3 with sunflower oil and 1% protein solutions containing WPI, SC, PPI individual proteins and their blends (3:1, 1:1, 1:3). Changes in droplet size and zeta-potential were measured to investigate the emulsion stability. The interfacial composition, surface loads, and the protein adsorption behaviour were studied to analyse the interface. Furthermore, the dilatational rheology of the interface was studied as the interfacial properties play a critical role in emulsion stability. All proteins showed good emulsifying and stabilising abilities at pH=3, as they contributed to form emulsions with relatively small droplets (0.355-0.411µm), and prevented destabilisation for 2 weeks. Such results were related to the strong electrostatic repulsion between the droplets and the viscoelastic film formed by proteins. No synergistic or antagonistic effect was observed by using dairy and pea protein blends, indicating pea proteins could be used to partially replace the dairy proteins. A preferential adsorption of dairy proteins over pea proteins was found, with SC being the most dominating type at the interface due to the higher diffusion rate and structural flexibility. However, globular WPI and PPI formed stronger interfacial films than SC and its blend owing to the extensive intermolecular interactions.

Cereal β-glucans are soluble non-starch polysaccharides. Both the health benefits and industrial applications of β-glucan have been correlated to its capability of forming viscous solutions. Oxidative degradation has been demonstrated to be the critical factor that causes the viscosity drop of β-glucan solutions. In oats and barley, more than 90% of the phytate was found in the soluble fiber fraction, most of which is β-glucan. Phytate has chelating ability to form phytate-mineral complexes. Therefore, phytate has the potential to suppress iron-catalyzed oxidative reactions and is hypothesized to protect β-glucan from oxidative degradation. The aim of this research was to study the role of both intrinsic and added phytate in the oxidative degradation kinetics of β-glucan. Fenton reaction was used to induce oxidation in both oat β-glucan (OBG) and barley β-glucan (BBG) solutions. Degradation of OBG and BBG was indicated by the decrease in molecular weight and viscosity. When the concentration of hydrogen peroxide kept constant, the extent of OBG degradation was found to be greater with increased iron concentration. Most degradation occurred in the beginning of the oxidation and OBG degradation in the initial 3 hours fitted well in the second order kinetics. The reaction rate constant (k) which stands for the degradation rate demonstrated a positive relationship with the iron concentration. Intrinsic phytate in OBG had a protective effect on β-glucan degradation induced by Fenton reaction. After phytate removal by ion exchange resin, degradation of OBG solution became faster with the same amount of oxidative reagents. As to the degradation kinetics, under the same oxidative condition, the k value increased after phytate removal. Added phytic acid also had a protective effect on the degradation of BBG solution, but the effect was not as strong as the intrinsic phytate in OBG. Furthermore, the strength of the protection was related to the PA/iron ratio. When the PA/ iron ratio was 2:5 , there was no protective effect of added phytic acid observed on the degradation of BBG. When the PA/ iron ratio was 2, the added phytic acid had protective effect. When PA/ iron ratio was 1:5, the added phytic acid had a more profound protective effect. In summary, our results demonstrated that both intrinsic phytate and additional phytic acid had a protective effect against the oxidative degradation of β-glucan. Addition of phytic acid in a proper ratio is of importance to maintain the stability of products containing β-glucan. Phytate or phytic acid is commonly considered as an antinutrient related to the mineral bioavailability in food intake. This study however showed an anti-oxidant effect of phytate in β-glucan solutions which suggests that it may have a beneficial effect in physicological conditions.

The literature review dealt with the principles and methods for the evaluation of the quality of raw meat and meat product in different aspects. The factors influencing the quality of meat products were also involved. A new type of muscular dystrophy in broiler Musculus pectoralis, wooden breast, has been found in broilers. The dystrophy results in fibrinogenesis and thus local hardening in the muscle, but poses no health risk in human consumption. The aim of the study was to explore the maximal percentage of wooden breast that can be used in the meat products without causing a perceived quality defect. In the preliminary tests, wooden breast was incorporated with normal meat in different percentages to make sausage and chicken nuggets. Different methods of comminuting were also applied in the processing of wooden breast. The quality of the products was evaluated through the measuring in different aspects. Comparison was made between normal products and products containing wooden breast, so that a maximal addition percentage of wooden breast was obtained. The results of the preliminary test were later verified in the pilot plant. The addition of wooden breast increased the shear force and binding strength of the sausage and finely chopped chicken nuggets but resulted little change on the shear force and binding strength of the ground chicken nuggets. The pH, redness, and yellowness of all types of products declined with the wooden breast treatment. Lightness of the products was increased by wooden breast. Through the verification in the pilot plant, sausage and two types of chicken nuggets allow the addition of wooden breast to replace at least 15% and 30% of the lean meat in the recipe, respectively. Due to the low incidence of the dystrophy, that high additions will not be necessary in the practice.

Bifidobacteria confer various health benefits to the host. Bifidobacterial growth can be promoted by caseinomacropeptide (CMP), which is the potential oligosaccharides-bearing portion of the κ-casein (κ-CN) in milk. This project was carried out to study the utilization of bovine glycosylated CMP by Bifidobacterium infantis ATCC 15697, B. bifidum ATCC 29521, and B. longum ATCC 15707 as well as to investigate the growth-promoting effect of CMP on these strains. Two types of media, namely the basal chemically-defined medium (bCDM) and the nutrient-rich medium known as de Man-Rogosa-Sharpe (MRS), were employed to achieve respective research objectives. The formula of the bCDM was developed by addition technique. It was found that L-cysteine, magnesium and manganese were needed by all the strains, and additionally, thiamin and nicotinic acid were essential for the growth of B. bifidum ATCC 29521. Since more than 70% of the glycosylated chains attached to a CMP are terminated with sialic acid residues, the cell counts and bound sialic acid contents in the media after incubation were analysed. Higher cell counts and lower bound sialic acid contents were found in the inoculated media supplemented with CMP as compared to unsupplemented group. Unexpectedly, slower microbial death, instead of growth, was observed in all inoculated bCDM+CMP in comparison to bCDM. It was also surprising to discover that B. bifidum ATCC 29521 and B. longum ATCC 15707 can utilize the glycosylated chains despite that no sialidase has ever been isolated from them. As a conclusion, B. infantis ATCC 15697 can cleave and utilize sialic acids, but not other glycans, that are attached to the glycosylated CMPs; while both B. bifidum ATCC 29521 and B. longum ATCC 15707 can cleave terminal sialic acid residues, followed by the utilization of the glycans attached to the glycosylated CMPs other than sialic acids. It was also found that bovine CMP can exert a similar growth-promoting effect on all three strains. From an industrial point of view, it is feasible to add the bovine CMP into the bifidobacterial growth medium to enhance their growth. Further study is warranted to characterize the sialidases present in B. bifidum ATCC 29521 and B. longum ATCC 15707.