Browsing by Subject "elintarviketieteet"

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  • Ahlberg, Sara (Helsingin yliopisto, 2020)
    Aflatoxins continue to be a food safety problem globally, especially in developing regions. Prevalent food contaminating aflatoxins are B1 (AFB1) and M1 (AFM1). These are human carcinogens and have potentially severe health impacts. Almost all (99.5 %) milk samples from Nairobi were contaminated with AFM1, highlighting the urgent need to create functional solutions to improve food safety. Based on the aflatoxin levels and milk consumption, risks were calculated: cancer risk caused by AFM1 was lower among consumers purchasing from formal markets (0.003 cases per 100,000) than for low-income consumers (0.006 cases per 100,000) purchasing from informal markets. Overall cancer risk (0.004 cases per 100,000) from AFM1 alone was low. Because of AFM1 in milk, 2.1 % of children below three years in middle-income families, and 2.4 % in low-income families, could be stunted. Overall, 2.7 % of children could hypothetically be stunted due to AFM1 exposure from milk. Based on these results AFM1 levels found in milk could contribute to an average of -0.340 height for age z-score reduction in growth. The exposure to AFM1 from milk is 46 ng/day on average, but children bear higher exposure of 3.5 ng/kg bodyweight (bw)/day compared with adults, at 0.8 ng/kg bw/day. Aflatoxins are produced by Aspergillus flavus fungus, which is prevalent in soils. Certain strains of lactic acid bacteria (LAB) have been reported inhibiting fungal growth. 171 LAB strains were tested against aflatoxin producing A. flavus fungi. The three LAB strains showing the highest antifungal activity were identified as Lactobacillus plantarum. None of the strains was able to completely inhibit fungal growth under conditions favorable for fungi and suboptimal for LAB. The three indigenous LAB Lactobacillus strains and one Lactococcus strains were tested for their AFM1 binding abilities in different conditions and after different treatments along with two reference Lactobacillus strains. The binding of AFM1 by LAB strains varied between 11 to 100 % in the biocontrol solution analysis, being approximately at the level of 40 % throughout the analysis sets. A significant amount of effort and resources have been invested in an attempt to control aflatoxins. However, these efforts have not substantially decreased the prevalence nor dietary exposure to aflatoxins in developing countries. The growth reduction of aflatoxin producing fungi with LAB could be one potential option, but there are still major issues to solve prior to any practical applications. A different approach to control aflatoxins suggesting the usage of binding agents in foods and lactic acid bacteria (LAB) have been studied extensively for this purpose. However, when assessing the results comprehensively and reviewing the practicality and ethics of use, risks are evident, and concerns arise. In conclusion, there are too many issues with using LAB for aflatoxin binding for it to be safely promoted. Arguably, using binders in human food might even worsen food safety in the longer term. A more comprehensive food safety approach has to be taken to solve this ongoing crisis.
  • Chamlagain, Bhawani Shankar (Helsingfors universitet, 2011)
    Dynamics of raw milk associated bacteria during cold storage of raw milk and their antibiotic resistance was reviewed, with focus on psychrotrophic bacteria. This study aimed to investigate the significance of cold storage of raw milk on antibiotic-resistant bacterial population and analyse the antibiotic resistance of the Gram-negative antibiotic-resistant psychrotrophic bacteria isolated from the cold-stored raw milk samples. Twenty-four raw milk samples, six at a time, were obtained from lorries that collected milk from Finnish farms and were stored at 4°C/4 d, 6°C/3 d and 6°C/4 d. Antibiotics representing four classes of antibiotics (gentamicin, ceftazidime, levofloxacin and trimethoprim-sulfamethoxazole) were used to determine the antibiotic resistance of mesophilic and psychrotrophic bacteria during the storage period. A representative number of antibiotic-resistant Gram-negative isolates retrieved from the cold-stored raw milk samples were identified by the phenotypic API 20 NE system and a few isolates by the 16S rDNA gene sequencing. Some of the isolates were further evaluated for their antibiotic resistance by the ATB PSE 5 and HiComb system. The initial average mesophilic counts were found below 105 CFU/mL, suggesting that the raw milk samples were of good quality. However, the mesophilic and psychrotrophic population increased when stored at 4°C/4 d, 6°C/3 d and 6°C/4 d. Gentamicin- and levofloxacin-resistant bacteria increased moderately (P < 0.05) while there was a considerable rise (P < 0.05) of ceftazidime- and trimethoprim-sulfamethoxazole-resistant population during the cold storage. Of the 50.9 % (28) of resistant isolates (total 55) identified by API 20 NE, the majority were Sphingomonas paucimobilis (8), Pseudomonas putida (5), Sphingobacterium spiritivorum (3) and Acinetobacter baumanii (2). The analysis by ATB PSE 5 system suggested that 57.1% of the isolates (total 49) were multiresistant. This study showed that the dairy environment harbours multidrug-resistant Gramnegative psychrotrophic bacteria and the cold chain of raw milk storage amplifies the antibioticresistant psychrotrophic bacterial population.
  • Gürbüz, Göker (Helsingfors universitet, 2010)
    The literature review elucidates the mechanism of oxidation in proteins and amino acids and gives an overview of the detection and analysis of protein oxidation products as well as information about ?-lactoglobulin and studies carried out on modifications of this protein under certain conditions. The experimental research included the fractionation of the tryptic peptides of ?-lactoglobulin using preparative-HPLC-MS and monitoring the oxidation process of these peptides via reverse phase-HPLC-UV. Peptides chosen to be oxidized were selected with respect to their amino acid content which were susceptible to oxidation and fractionated according to their m/z values. These peptides were: IPAVFK (m/z 674), ALPMHIR (m/z 838), LIVTQTMK (m/z 934) and VLVLDTDYK (m/z 1066). Even though it was not possible to solely isolate the target peptides due to co-elution of various fractions, the percentages of target peptides in the samples were satisfactory to carry out the oxidation procedure. IPAVFK and VLVLDTDYK fractions were found to yield the oxidation products reviewed in literature, however, unoxidized peptides were still present in high amounts after 21 days of oxidation. The UV data at 260 and 280 nm enabled to monitor both the main peptides and the oxidation products due to the absorbance of aromatic side-chains these peptides possess. ALPMHIR and LIVTQTMK fractions were oxidatively consumed rapidly and oxidation products of these peptides were observed even on day 0. High rates of depletion of these peptides were acredited to the presence of His (H) and sulfur-containing side-chains of Met (M). In conclusion, selected peptides hold the potential to be utilized as marker peptides in ?-lactoglobulin oxidation.
  • Koivusaari, Katariina (Helsingin yliopisto, 2021)
    Cow’s milk has been associated with the development of both type 1 diabetes and asthma in children, although in different ways. Consumption of cow’s milk has been associated with an increased risk of the development of type 1 diabetes. On the other hand, several cross-sectional studies show that consumption of raw, unprocessed milk is associated with a decreased risk of asthma or atopy when compared to no consumption of raw milk or to consumption of sterilized milk. Little is known about differently processed milk products. The aim of this thesis was to study, in a birth cohort setting, whether the consumption of differently processed milk products is associated with the risk of islet autoimmunity or asthma in children. To study that, a novel processing-based classification of milk products was created in the national food composition database as part of this thesis. This classification was also used to evaluate children’s consumption of differently processed milk products, as such information was lacking. This thesis is based on the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) Nutrition Study, comprising children genetically predisposed to type 1 diabetes born in Tampere or Oulu University hospitals from 1996 to 2004 (N=6081). The nutritional information of the participants was collected by food records at the age of 3 and 6 months, and 1, 2, 3, 4, 5, and 6 years. The consumption of milk products was calculated from the food records using the national food composition database. Each milk product item in the national food composition database was classified according to the adopted heat-treatment (low-pasteurized or less heated/high-pasteurized at <100°C/high-pasteurized at 100°C or sterilized) and homogenization (yes/no/fat-free). The classification was done principally based on literature. The study participants were followed for type 1 diabetes-related autoantibodies regularly until the age of 15 years. The primary outcome in the diabetes-related study was islet autoimmunity by the age of 6 years, defined as repeated positivity for islet cell autoantibodies and at least one biochemical antibody tested: insulin autoantibodies, antibodies to the 65 kD isoform of glutamic acid decarboxylase, and the tyrosine phosphatase-related islet antigen-2 molecule. The secondary outcome was islet autoimmunity by the age of 15 years. Of the 6081 children within the DIPP Nutrition Study, 4075 children were still in the DIPP follow-up at the age of 5 years, and of them 3781 participated in the DIPP Allergy and Asthma Study. The information on asthma was collected at the age of 5 years by using an ISAAC-based questionnaire. Outcomes in the asthma study were asthma, atopic asthma, and nonatopic asthma by the age of 5 years. Asthma was defined as doctor-diagnosed asthma plus wheeze or use of asthma medication during the preceding 12 months. Atopic asthma was defined as IgE-positive asthma, and nonatopic asthma as IgE-negative asthma. Joint models for longitudinal and time-to-event data were used as the statistical approach to study the association between consumption of differently processed milk products and islet autoimmunity and asthma. Almost all study participants [e.g., at the age of 3 years, 3401 of 3460 (98.3%)] consumed cow’s milk. During the first year of life, high-pasteurized at 100°C or sterilized milk products were consumed in higher amounts, while at ages 1–6 years low-pasteurized milk products were predominant. Homogenized milk products were consumed in higher amounts than nonhomogenized ones. Consumption of fat-free milk products increased by age. By the age of 6 years, islet autoimmunity developed in 246 (4.4%) of the 5545 children included in the analyses. High consumption of cow’s milk products was associated with an increased risk of islet autoimmunity [energy-adjusted hazard ratio (95% confidence intervals) 1.06 (1.02, 1.11)]. In addition, consumption of nonfermented [1.06 (1.01, 1.10)], fermented [1.35 (1.10, 1.67)], and homogenized [1.07 (1.02, 1.12)] milk products were associated with an increased risk. No processing type stood out as a particular risk factor. Asthma developed in 184 (6.0%) of the 3053 children included in the analyses, by the age of 5 years. Asthma in 101 (54.9%) children was atopic, and in 75 (40.8%) children nonatopic. The asthma type of 8 (4.3%) children could not be categorized. Consumption of high-pasteurized at 100°C or sterilized milk products [adjusted hazard ratio (95% confidence intervals) 1.06 (1.01, 1.10)] including milk-based infant formulas [1.15 (1.07, 1.23)] was associated with an increased risk of asthma. Consumption of cow’s milk products [1.09 (1.03, 1.15)], nonfermented milk products [1.08 (1.02, 1.14)], infant formulas [1.23 (1.13, 1,34)], and high-pasteurized at 100°C or sterilized milk products [1.08 (1.02, 1.15)] were associated with an increased risk of nonatopic asthma. In parallel to several previous studies, the results of this thesis suggest that high consumption of cow’s milk and cow’s milk products is associated with the development of the two immunological diseases in children. Processing of milk did not play a significant role in the association to islet autoimmunity. The consumption of high-pasteurized at 100°C or sterilized milk products was associated with an increased risk of asthma. No such association was seen for low-pasteurized milk products. This implies that processing may change the immunological properties of milk and thus play a role in the development of immunological diseases. As milk and milk products are commonly used in substantial amounts by Finnish children, future studies are needed to confirm the results and to enlighten the mechanisms behind the associations.
  • Ylä-Ajos, Maria (Helsingin yliopisto, 2006)
    Muscle glycogen exists in two forms: low molecular weight pro-glycogen and high molecular weight macro-glycogen. The degradation of glycogen to glucose 1 phosphate and free glucose is catalysed by glycogen phosphorylase together with glycogen debranching enzyme (GDE). The process in which glycogen is broken down via anaerobic pathways to lactate, results in the acidification of the muscles and has a great influence on meat quality. Thus, the overall aim of this thesis was to characterise the post mortem action of GDE in muscles of meat production animals (pigs, cattle and chickens). Interest was focused on the differences in GDE activity between fast twitch glycolytic muscles and slow twitch oxidative muscles. The effects of pH, temperature, RN genotype (PRKAG3 gene), and of time post mortem on GDE activity were also investigated. This thesis showed that there are differences in GDE activity between animal species and between different muscles of an animal. It was shown that in pigs and cattle, higher GDE activity and phosphorylase activity exists in the fast twitch glycolytic muscles than in slow twitch oxidative muscles of the same animal. Thus, the high activity of these enzymes enables a faster rate of glycogenolysis in glycolytic M. longissimus dorsi compared to oxidative M. masseter. In chicken muscles, the GDE activity was low compared to pig or cattle muscles. Furthermore, the GDE activity in the glycolytic M. pectoralis superficialis was lower than in more oxidative M. quadriceps femoris despite the high phosphorylase activity in the former. The relative ratios between phosphorylase and GDE activity were higher in fast twitch glycolytic muscles than in slow twitch oxidative muscles of all studied animals. This suggests that the relatively low GDE activity compared to the phosphorylase activity in fast twitch glycolytic muscles may be a protection mechanism in living muscle against a very fast pH decrease. Chilling significantly decreased GDE activity and below 15 C porcine GDE was almost inactive. The effect of pH on GDE activity was only minor at the range normally found in post mortem muscles (pH 7.4 to 5.0). The GDE activity remained level for several hours after slaughter. During the first hours post mortem, GDE activity was similar in RN- carrier pigs and in wild type pigs. However, the GDE activity declined faster in M. longissimus dorsi from wild type pigs than in the RN carrier pigs, the difference between genotypes was significant after 24 h post mortem. Pro-glycogen and macro-glycogen contents were higher, pH decrease was faster and ultimate pH was lower in RN- carrier pigs than in wild type pigs. In the RN- carriers, the prolonged high GDE activity level may enable an extended pH decrease and lower ultimate pH in their muscles. In conclusion, GDE is not the main factor determining the rate or the extent of post mortem glycogenolysis, but under certain conditions, such as in very fast chilling, the inhibition of GDE activity in meat may reduce the rate of pH decrease and result in higher ultimate pH. The rate and extent of pH decrease affects several meat quality traits.
  • Kirjoranta, Satu (Helsingin yliopisto, 2020)
    The structure of a common cereal-based crispy snack product can be defined as solid foam. Consumption of such snack products has become popular especially among teenagers and young adults. At the same time obesity has become a common problem. Conventional snack products consist mainly of starch and fat and they have very low protein and dietary fiber content. It is known that dietary fiber and protein have many health effects and they can help in losing weight by avoiding the feeling of hunger. It is therefore important to develop products with high protein and fiber content which can be used instead of common low nutritional value snack products. The aims of this academic research were to utilize several fiber and protein sources in order to produce snack products using extrusion cooking technology which is a common way to produce foods. Special attention was paid to using by-products from the food industry and ingredients which are not commonly used in snacks. Snack products were prepared with extrusion cooking technology in several trials with various mixtures of ingredients. Studied ingredients were: whole grain barley flour, defatted whole grain and endosperm oat flour, corn flour, differently treated oat bran concentrate fractions (OBC), brewer´s spent grain from barley (BSG), polydextrose (PD), whey protein isolate (WPI), Peruvian pseudocereals (amaranth, quinoa, kañiwa), barley starch and waxy corn starch. Snack products were prepared by varying several extrusion parameters: water content of the mass, screw speed and temperature of section 6 and die. Effects of extrusion parameters on the process (torque, specific mechanical energy and pressure at the die) and on the properties (water content, expansion, hardness) of the snacks were studied using response surface methodology. Properties of the most expanded products were studied in more detail. Several fiber sources could be used in the production of snacks, but high fiber content made snacks hard and poorly expanded. However, expanded and crispy barley-based snacks with high fiber and protein content were obtained by adding starch or WPI. Extrusion cooking was also found to increase the extractability and viscosity of barley β-glucan. Furthermore, water-soluble OBC increased the expansion of extrudates made of defatted endosperm oat flour. Expanded, crispy gluten free snack products could be prepared using defatted oat endosperm flour with water-soluble OBC or corn flour enriched with Peruvian pseudocereals at content of 20% of solids. Even though ingredients had a great effect on the properties of the snacks, structure could be modified by extrusion variables: increasing screw speed and decreasing water content of the extruded mass increased expansion and decreased hardness of the snack products. This research gave information how fiber and protein rich ingredients for example by-products could be utilized in the production of healthy snacks made by extrusion cooking.
  • Maina, Ndegwa Henry (Helsingin yliopisto, 2012)
    Over the past few years, interest in dextrans produced by lactic acid bacteria (LAB) has experienced a renaissance because of their prospective application as natural hydrocolloids in fermented products. Though the benefits of dextrans as hydrocolloids in sourdough bread have been the subject of several studies, only in a few of these studies have the structural features of the potential dextrans been elucidated. In this thesis the structure and macromolecular properties of W. confusa E392 and L. citreum E497 dextrans were studied to understand their functionality in sourdough. Since functionality also depends on concentration, an enzyme-assisted assay was developed to estimate the amount of dextrans produced in sourdough. The experimental part included several other dextrans for comparison and method development. Structural analysis revealed that W. confusa E392 dextran contains few α-(1→3)-linked branches (3%), while L. citreum E497 dextran contains α-(1→2)- and α-(1→3)-linked branches (11% and 4%, respectively). Further details on the nature of these branches from the analysis of structural segments indicated that the α-(1→3)-linked branches in both dextrans are either a single unit or elongated by two or more α-(1→6)-linked glucosyl residues. Macromolecular characterization in aqueous solutions showed them to be high molar mass dextrans (107 g/mol). In dimethylsulfoxide (DMSO), however, the molar mass of the dextrans was lower (1.5 and 1.9 × 106 g/mol). The lower values in DMSO were considered to originate from individual dextran chains, while the values obtained in aqueous solutions were skewed by the presence of compact aggregates. The enzyme-assisted assay developed for dextran quantification was limited to dextrans with few branch linkages. L. citreum E497 dextran was therefore not quantifiable with this method. During 17-24 hours of fermentation, W. confusa E392 produced 1.1-1.6% dextran from an initial 10% sucrose. Preliminary studies indicate that the strain channeled the remaining glucose (the theoretical maximum glucose was 5%) to the production of oligosaccharides via dextransucrase acceptor reactions with maltose. In conclusion, the study revealed that despite their simple monosaccharide composition, dextrans have a complex ramified structure even in the case of W. confusa E392 that only has a few branch linkages. Aqueous solutions of high molar mass dextrans contain compact aggregates, which, in addition to the ramified structure of dextrans, complicate their macromolecular characterization. Consequently, deducing the functional properties of dextrans in sourdough or any other food application is not straightforward. When comparing the functional properties of dextrans, the size (hydrodynamic properties and intrinsic viscosity), which reflects the shape and conformation of the dextrans, should be considered in addition to molar mass and structural features. Since food applications are aqueous systems, the functionality of dextrans may result from a contribution of both the properties of individual chains and compact aggregates.
  • Nurmi, Tanja (Helsingin yliopisto, 2012)
    Phytosterols are plant-derived bioactive compounds known for their serum cholesterol-lowering ability and other health benefits. Phytosterols may occur as free sterols or various conjugates, e.g. ferulic acid esters. Cereals are an important source of natural phytosterols and sterol conjugates. However, the variation in occurrence and distribution of these compounds in cereal grains has not been adequately studied. As a part of the EU FP6 project HEALTHGRAIN, the effects of genotype, environment and dry fractionation on phytosterol and steryl ferulate contents in wheat kernels were studied. Wheat genotypes were grown at one location in Hungary over three consecutive years (2005 to 2007) and at three additional locations in Europe (Poland, France and the United Kingdom) in 2007. In 2005, 175 wheat lines were included in the diversity screen trial, and selected lines were further studied for environmental variation, focusing on bread wheat. Variation within wheat grains was studied by analysing wheat and bran fractions produced by novel and conventional dry fractionation processes. All genotypes and fractions were analysed for phytosterols using GC-FID and selected ones for steryl ferulates using HPLC-UV. The contents and compositions of sterol compounds in wheat were significantly affected by the genetic factors and growing location, whereas no considerable year-to-year variation was observed. The highest phytosterol contents were observed in ancient einkorn wheat and durum wheat genotypes and the lowest in bread wheat lines. Bread wheat contained 670 - 959 µg/g DM phytosterols, of which 7 - 9% occurred as steryl ferulate conjugates (79 - 123 µg/g DM), when grown at a single location during one year. Within various environments, the highest levels of sterol compounds were observed in genotypes cultivated in Hungary, and the lowest in those cultivated in the UK and France. Sitosterol was the main sterol species and the widest variation was observed in the stanol contents. Stanol species were the main compounds in the steryl ferulate fraction. Small kernels with a high bran content contained higher levels of sterol compounds than large ones. The contents and compositions of wheat fractions varied substantially, with the total contents of phytosterols and steryl ferulates ranging 6- and 120-fold, respectively. Phytosterols and steryl ferulates were concentrated in the bran. Within the bran layers, phytosterols were accumulated in the intracellular contents of the aleurone layer and intermediate layers, whereas steryl ferulates accumulated in the intermediate layers. Knowledge of the natural variation of phytosterol compounds in wheat enables the selection of wheat varieties and fractions with high and stable phytochemical content. Exploitation of such wheat grains or fractions in cereal foods would increase the intake of bioactive compounds and enhance public well-being and health in a natural way.
  • Väistö, Anne (Helsingfors universitet, 2010)
    The properties and evaluation methods of viili, the actions and interactions of viili starters in milk and bacteriophages of the viili starters were reviewed. The aim of the experimental study was to explore whether it was possible to make viili with single strain starters and combine them just before adding the starter to the milk. A new, second viili starter was made from the new strains. The success of the new starters was evaluated by sensory evaluation and by analysing the texture and chemical properties of viili. The starter strains were cultivated in a bioreactor, concentrated by a centrifuge and frozen at –75 °C. The starter strains were combined approx. 1 day before the viili production. The sensory evaluation of the viili was performed by groups of 3 to 6 persons. The texture (consistency, firmness and cohesiveness) of the viili and chemical analysis were made. The results of the sensory analysis were analysed statistically and new strain combinations were formulated based results. The viilis made by the traditional viili starter strains were evaluated by the triangle test (n = 10–11) and the second viili starter was evaluated by descriptive analysis (n = 8). The texture measurements and chemical analyses were also performed. The viili produced by the second starter was infected by the factory phage samples and the pH was measured. After infecting the viili with phage samples, the viili produced by second starter was acidified to pH 4.5 from 0 to 10 hours later compared to the viili without the phage sample. The viili produced by traditional starter did not acidify when the phage was added. The aroma producers did not grow properly in viili when the starter was made by single strains. The viilis made by the present viili starter strains were not distinguished by the triangle test which meant that the starters are possible to make from single strains. The viilis produced by the second viili starter differed from the viili made by traditional starter by appearance and texture characteristics. There was no difference in taste characteristics between the traditional and new starter.