Maatalous- metsätieteellinen tiedekunta


Nyligen publicerat

  • Vanhatalo, Anni (2018)
    Plants synthesise thousands of biogenic volatile organic compounds (BVOCs) as part of their secondary metabolism. Scots pine (Pinus sylvestris) particularly produces mono- and sesquiterpenes, which are mainly stored in oleoresin in resin ducts. In this study, the monoterpene emission rate from stems was found to increase as a function of increasing resin pressure, which was positively correlated with the air temperature and foliage transpiration rate. Monoterpene synthase activity describes the maximum monoterpene production potential. The seasonal cycle and needle age were observed to explain the majority of the variation in needle monoterpene synthase activities, monoterpene storage pools and monoterpene emissions from shoots. Variation in the monoterpene concentration between seasons, different needle age classes and different trees was observed to be minor. Monoterpene synthase activity was higher in <1-year-old needles compared to older ones. Within a single tree, the compound-specific composition of monoterpene synthase activities and monoterpene storages was not reflected in the composition of emissions. For example, the share of δ-3-carene was substantially higher in the emissions than in the storage pools and synthase activities. An automated enclosure measurement system including a proton transfer reaction mass spectrometer was utilized to follow the VOC emissions from the woody compartments of trees over several years. This was the first study to quantify such emissions for an extended period. Scots pine stems were observed to emit monoterpenes and methanol into the ambient air. The fluxes displayed a seasonal cycle: methanol emissions were highest in the midst of the growing season, whereas monoterpene emissions peaked not only on the hottest summer days, but also in the spring when the photosynthetic capacity of trees recovered. The emissions of some monoterpenes exhibited distinct diurnal patterns in their enantiomeric compositions. The above-canopy air terpene concentrations reflected the emission rates from trees, the atmospheric reactivities of the compounds, the tree species composition of the measurement site and the abundances of different tree chemotypes.
  • Teikari, Jonna (Helsingin yliopisto, 2018)
    The Baltic Sea is a shallow brackish water ecosystem. It is naturally prone to eutrophication, and massive cyanobacterial blooms are an annual phenomenon in this region. Blooms are toxic to humans and animals, and cause economical losses and harm for recreational users. Almost all cyanobacteria are photoautotrophic organisms, and many bloom-forming Baltic Sea cyanobacteria can additionally fix atmospheric nitrogen. Inorganic phosphorus is usually the first and most important growth-limiting factor. Monitoring the external phosphorus inflow is strictly implemented by the coastal states, but uneven point load still occurs. In addition, a heavy and long-term phosphorus load has resulted in substantial phosphorus reservoirs in the sediments and phosphorus can be circulated back to the waterbody. Cyanobacterial blooms in the Baltic Sea are dominated by Aphanizomenon sp., Dolichospermum sp., and Nodularia spumigena, of which Dolichospermum sp. and N. spumigena can produce toxins. Due to their evolutionary history, Dolichospermum sp. is more abundant in the less saline coastal regions, whereas N. spumigena dominates in the open sea. This work studied the effects of changing environmental conditions on the distribution and niche adaptation strategies of toxic and bloom-forming Baltic Sea cyanobacteria using state-of-the-art sequencing and molecular biology methods. Climate change models have predicted that the salinity of the Baltic Sea will possibly decline in the future, and thus the behavior of Dolichospermum sp. and N. spumigena was studied in unfavorable salinities. Comparative genomic analysis showed that Dolichospermum sp. has high synteny between its freshwater counterparts, and possibly therefore the strain was unable to proliferate in moderate salinities. Salt addition induced massive transcriptional shifts, especially within the photosynthesis and nitrogen-fixing pathways. Moreover, moderate salinity increased the production of microcystins and triggered the oxidative stress response. On the contrary, N. spumigena thrived in higher salinities, and its growth and metabolism were hindered by freshwater. Unique sigma factors and an elevated number of transposases were identified in the genome of N. spumigena, suggesting a high genetic capacity to adapt to changing salinities and brackish water conditions. The growth and metabolism of Dolichospermum sp. and N. spumigena were arrested under limited availability of inorganic phosphorus. Both strains upregulated the genes in the pho regulon, indicating that these genes can be used for determining the phosphorus status of cyanobacterial blooms. All studied strains of N. spumigena from the Baltic Sea carried the phnC-M gene cluster, which is responsible for the transport and utilization of the highly stable phosphonates. Naturally produced phosphonates were an additional phosphorus source for N. spumigena cyanobacteria, and produced a competitive advantage in phosphorus-limited conditions. However, methane, an organic remnant of methylphosphonate was released to the gaseous environment. Blooms of N. spumigena cyanobacteria may thus explain the elevated summertime methane concentration in the Baltic Sea. The results presented in this thesis suggest that cyanobacterial blooms will continue to appear in the future if sufficient amount of phosphorus is present but community composition may shift towards freshwater species as a consequence of climate change.
  • Kaakkurivaara, Tomi (Helsingin yliopisto, 2018)
    The aim of this thesis was to investigate the use of portable bearing capacity measurement devices and alternative fly ash structures to improve forest road quality and rehabilitation practices. So far, few tools have proved suitable for practical evaluation of forest road trafficability. Bearing capacity is the main component of trafficability and bearing capacity measurements are rarely conducted on forest roads. Replacing subjective criteria with objective measurement methods is the first step towards avoiding rutting damages as well as improving rehabilitation decisions. Three bearing capacity measuring devices were tested for predicting forest road rutting in the context of bearing capacity improvements with fly ash structures. Modulus of elasticity (E-modulus) was used as the measurement unit. E-modulus was used to quantify road stiffness as measured by two portable measurement devices and one trailer-mounted device. A light falling weight deflectometer (LFWD) and a dynamic cone penetrometer (DCP) were used to challenge the conventional falling weight deflectometer (FWD). Test sections were located on forest roads with both mineral and peat subgrades. The comparison showed logical correlations between the measured E-modulus values, and reliable regression models are presented for the differences between measuring devices. In most cases DCP and LFWD can be utilized on forest roads instead of the expensive FWD. The measurement results for the portable devices and the FWD were compared to rutting, as represented by the increases in rut depth per passing truck (mm/pass) measured by mobile laser scanning (MLS). The devices were used to quantify the relationships between the E-modulus and rutting. Rutting threshold values were then based on these relations. A rough rutting susceptibility table was outlined to aid forestry professionals to estimate the rutting damage risk per timber truck on forest roads during periods of thaw-weakening. Growing bioenergy production and consumption has resulted in an increase in the amount of fly ash produced by the forestry sector. At the same time the cost for ash deposition at land-fills has increased considerably. Utilizing fly ash in forest roads is therefore seen as a potentially cost-efficient alternative for improving bearing capacity. The fly ash part of the study investigated therefore road rehabilitation work from both technical and economical perspectives. Four different rehabilitation methods were tested using wood- and peat-based fly ash. The four rehabilitation methods involved two structures mixed with aggregate and two structures with uniform fly ash. The resulting bearing capacity of the rehabilitated road sections was improved compared to the reference sections, especially for the mixed structures. The improvements were verified by statistical comparisons. The study also defined the various work phases of rehabilitation and estimated construction costs based on phase-specific machine productivities. Cost calculation equations were established for earthwork and the transportation of construction materials. The lowest construction costs were calculated for a 250-mm thick uniform layer of fly ash structure, however, a 500-mm thick uniform layer of fly ash provided the lowest total costs when taking into consideration the alternative cost for landfill deposition.
  • Berka, Anna (Helsingin yliopisto, 2018)
    This dissertation explores the governance, local impacts and costs of community-owned renewable energy (CRE). The objective is to understand if and in what context collective local ownership models represent a feasible and effective means to operationalising a more ‘sustainable development’ in the renewable energy sector and beyond. The articles draw on a range of fields, from energy governance and project economics to impact evaluation. Specific methodologies used are systematic literature review, discourse analysis, historical institutional analysis and risk-extended net present valuation. Unique contributions of this work are a meta-level understanding of the community energy sector in the UK and an understanding of its emergence in context of technological and institutional change. In addition, it provides an explicit assessment of Quality of Evidence problems in this subfield of energy and social science research, placing it firmly in the context of current literature and methods in project economics and impact evaluation. Findings show that ownership patterns in the energy sector are precarious and subject to changing narratives that emerge in response to domestic socio-economic and political dilemma’s, exogenous shocks, and emerging economic schools of thought. CRE projects have the potential to generate a variety of positive local impacts that vary depending on the motivation and management of projects and project revenues. Under certain conditions CRE can empower community organisations to address systemic socio-economic problems in the public domain. Finally, in a competitive market setting and where CRE is implemented by newly-established grassroots organisations, projects face a range of risks that commercial projects do not, and that erode their financial viability. As such, the development and expansion of community renewable energy as a substantial proportion of the energy sector requires policy makers to assign it special status and provide policy support on the basis of its local social, economic and environmental benefits. Policy support for community renewable energy requires a willingness to integrate energy and social policy domains.
  • Kemppinen, Asmo (Helsingin yliopisto, 2018)
    Short-chain triacylglycerols (SC-TAGs) comprise at least one esterified fatty acid with two to six carbon atoms. A high molar proportion of SC-TAGs in bovine milk fat (MF) is a unique feature among edible fats and oils and results in characteristic biological, chemical, physical, and technological properties of MF. Further, high content of SC-TAGs induces specific requirements for TAG analysis. The main objective of the present study was to develop chromatographic (gas chromatography, GC; normal-phase high-performance liquid chromatography, np-HPLC) and mass spectrometric (MS) (electron ionization MS, EI–MS; electrospray ionization MS, ESI–MS/ESI–MS/MS) methods to separate, identify, and quantify regio- and acyl chain isomers of SC-TAG species in model TAG mixtures and in butterfat (BF). An improved method was developed to fractionate BF TAGs into saturated, monoene, and polyene TAGs on a solid-phase extraction column in silver ion mode prior to GC and GC–EI–MS. This method enabled quantification of otherwise coeluting regio- and acyl chain isomers of SC-TAG species with the same number of acyl carbons but different degree of unsaturation. The elution order of the acyl chain isomers of isobaric TAG species and the regioisomers of SC-TAGs on a polarizable phenyl(65%)methylsilicone GC-column was empirically established using retention indices calculated for a high number (112) of synthesized TAG species and isomers. Separation power of the column proved to be high enough to resolve the regioisomers of mono-SC-TAGs. Correspondingly, np-HPLC was shown to resolve the regioisomers of mono- and dibutyryl TAGs to the baseline, monocaproyl TAGs close to the baseline, and dicaproyl TAGs partially. Even few regioisomer pairs of long-chain TAGs containing fatty acyl 20:0 were resolved as well. The present study established that in ESI–MS/MS, the cleavage of SC-acyls (4:0, 6:0) from the sn-1(3) positions of mono-SC-TAGs was at least 2.3 times higher than that from the sn-2 position, hence enabling clear-cut differentiation between regioisomers. Due to intricate TAG composition of BF specific molar correction factors (MCFs) were used in quantification of TAGs by GC, GC–EI–MS, and np-HPLC–ESI–MS. In both MS methods, extensive variation in MCFs was observed due to different molecular size, degree of unsaturation, and regio- and acyl chain isomerism of TAGs, but substantial number (>100) of empirically determined MCFs enabled extrapolation of MCFs for more uncommon TAGs. Both MS methods provided new information that emphasized the need to use specific MCFs for the sn-1(3) and sn-2 TAG isomers. All quantification methods yielded relatively unsurprising and similar general distribution of TAG classes and selection of the most common TAG species in BF. However, 64 minor TAGs of 336 even-numbered TAG species that were determined by np-HPLC–ESI–MS were confirmed for the first time to exist in BF. A high number of them were SC-TAGs including monoacetyl TAGs, rare sn-2 isomers of mono-SC-TAGs, and di- and tri-SC-TAGs. The present study suggested that the developed methods were reliable choices to determine both the most common TAGs and more rare TAGs in BF. All methods enabled quantification of the regioisomers of SC-TAGs in BF. The methods can be adapted to detect adulteration of MF, to elucidate biological or technological function of MF, and to develop effective procedures of MF modification. They can be applied to investigation of structured TAGs with short-chain fatty acyls.
  • Marcenaro, Delfia (Helsingin yliopisto, 2018)
    The common bean (Phaseolus vulgaris L.) is an important legume crop grown widely around the world due to its high nutritional values. In developing countries of Africa and Latin America (e.g. Tanzania and Nicaragua) bean crop is linked to food security and income generation especially in poorest groups made up of small farmers. Disease problems, pests, unimproved seeds, inappropriate agricultural management and environmental conditions are often the main constraints in bean crop production. In Nicaragua and Tanzania, the unavailability of certified seed of local bean varieties causes significant losses in yield and quality. Other limitation present in Nicaragua and Tanzania concerning bean diseases is that seed-borne fungi and viruses has gained little attention. Thus, for better understanding in seed-borne fungi and viruses associated with beans we investigated seed-borne fungi in an important new local bean variety. Sampling from four seed storehouses and six seed lots of cv. INTA Rojo was done in the main bean production areas in Nicaragua. In addition, to detect viruses infecting bean plants, we surveyed seedborne viruses in landraces and new common bean varieties introduced to Nicaragua (Central America) as well as improved varieties grown in Tanzania (eastern Africa). The main results for seedborne fungi included 87 pathogenic isolates from eight genera: Fusarium spp. (F. chlamydosporum, F. equiseti, F. incarnatum), Lasiodiplodia theobromae, Macrophomina phaseolina, Corynespora cassiicola, Colletotrichum capsici, Colletotrichum gloeosporioides, Diaporthe sp. (Phomopsis), Aspergillus flavus, and Penicillium citrinum. Subsequently, results based on germination in seed lots of common bean (‘INTA Rojo’) from four bean production areas in Nicaragua showed that germination was constantly less than 40% and could be as low as 16%, indicating disastrous yield losses for producers. Four different species-specific primer pairs to detect F. equiseti, F. chlamydosporum, F. incarnatum, C. capsici, C. gloesporiodes and C. cassiicola were developed in this study based on sequence alignment of the internal transcribed spacer sequences (ITS1 and ITS2) from different fungi. They were tested in pure cultures of fungi and used successfully in detection of fungal pathogens from infected plants. These specific primers are able to give the basis to be used in seed health inspection (seeds and plants) for further research of the epidemiology, ecology, and control of the pathogenic fungi of common beans in the field. The presence of Phaseolus vulgaris endornavirus 1 (PvEV-1) and PvEV-2 was detected in Nicaraguan and Tanzanian bean varieties. Likewise, Cowpea mild mosaic virus was detected in one region of Tanzania. There is apparently indication that the new Nicaragua bean varieties are carrying virus resistance genes because no seedborne viruses were found in them. In Tanzania improved protection against pathogenic seed-borne viruses is developed by resistance breeding. These findings are the first report showing that several pathogenic seed-borne fungi occur in Nicaraguan beans. Previously, little information has been available on pathogenic fungi such as F. equiseti, F. incarnatum, L. theobromae, C. cassiicola, and Diaporthe spp in Nicaraguan common beans. This study has contributed in taking first steps to improve the pathological and genetic components in the national seed production system in Nicaragua and Tanzania by providing new knowledge concerning seed-borne pathogens associated with common bean.
  • Coloma, Sebastián (Helsingin yliopisto, 2018)
    Biotic and abiotic factors are known to influence the formation of blooms by diazotrophic cyanobacteria, which may dramatically modify the nutrient environment affecting the pelagic food web and the plankton community. Abiotic factors, e.g. nutrient availability and weather conditions, have been widely studied and discussed. However, biotic factors such as the impact of phages remain less studied. This study aims to describe the effects of a Baltic Sea cyanophage on a filamentous cyanobacterium (Nodularia spumigena) and other aspects in plankton communities utilizing an experimental approach. Specifically, the study addresses bacteria-phage interactions, plankton community dynamics, and nitrogen transfer between the plankton components (phytoplankton species and rotifers) in the food web. To perform the experimental study, a Baltic Sea cyanophage infecting Nodularia was isolated, characterized and named 2AV2. The cyanophage 2AV2 belongs to the Siphovirus family with a lytic life cycle between 12–18 hours with a restricted host range of 12 out of 45 tested Nodularia strains. Lysis of the susceptible host caused an approximately 80% reduction in the cyanobacterial population resulting in selection for phage-resistant Nodularia cells. The evolution of phage resistance significantly reduced the release of nitrogen resulting from lysis of susceptible host cells in the presence of phage. In addition, isolates from the phage-resistant population had two morphotypes, short filaments (40%) and long filaments (60%), while the susceptible population only displayed long filaments. Further, differences between these morphotypes were detected in traits such as growth rate and buoyancy. The divergence in phenotypic traits among phage-resistant cyanobacteria is suggested to represent an evolutionary trade-off between phage resistance and fitness in the absence of phage. This is the first study to show a change in morphology (filament length) in Nodularia spumigena after the evolution of phage resistance. In an experimental plankton community, Nodularia, cyanophage 2AV2, Chlorella and rotifer biomasses developed differently between treatments with different initial frequencies of phage phage-resistant Nodularia, determining the ecological succession and nitrogen transfer in the food web. This study supports the hypothesis that cyanophages not only affect cyanobacterial populations but they also have a wider influence on plankton community dynamics and nitrogen transfer in food webs.
  • Gürbüz, Göker (Helsingin yliopisto, 2018)
    Oxidative reactions in food systems during processing and storage constitute a significant problem that determines the nutritional and sensory qualities of the food product as well as the textural and functional properties. Proteins and lipids, as essential components of foods, are highly prone to oxidative degradation that results in undesired modifications in food systems. Although lipid oxidation as a topic has been given a widespread attention, protein oxidation and its consequences in foods have been studied relatively recently. In particular, co-oxidation of food proteins and lipids, in terms of their interactions within the complex mechanism of oxidative reactions, has been gathering interest only lately. The behavior of proteins from various food sources and technological pre-treatments as well as the outcomes of this behavior under oxidative conditions in the presence of lipids is a much required subject on which to focus both by academia and industry. The purpose of this work was to elucidate the degradation of proteins and lipids within the oxidative system, and to characterize the consecutive modifications of oxidative interactions between food proteins and lipids in model investigations. In order to achieve this, experimental oxidation models were set up that investigate firstly the molecular level interactions between lipid oxidation product malondialdehyde (MDA) and whey protein, β-lactoglobulin (β-Lg) peptides. In this work, LC-MS/MS methods were employed to characterize and identify the interaction products. Later studies focused on the oxidative behavior of plant proteins such as quinoa, amaranth and faba beans, utilized in emulsification of rapeseed oil. Results from the analyses of primary and secondary volatile lipid oxidation products as well as tryptophan fluorescence of proteins were gathered to assess the oxidative process. The results of the first study showed that two distinct compounds were generated through Schiff-base adduct formation between MDA and β-Lg peptides, one of which had strong fluorescent properties. Emulsions studies demonstrated that amaranth proteins produced oxidatively and physically more stable emulsions compared to quinoa proteins. However, due to protein oxidation neither type of emulsions were as stable as the commercial emulsifier Tween®20. Emulsions with proteins of faba beans that had undergone pre-treatments were less oxidized compared to native samples which was due to hindering of the endogenous enzyme activity. Proteins located at the lipid droplet interface were degraded more than those in the water phase. This thesis demonstrates that interdependent relations between proteins and lipids such as adduct formation, free-radical transfer, and reactions between oxidized species have a significant effect on the overall course of oxidation of the food system which affect the final observed modifications. Therefore, customized solutions against oxidation should regard the intricate relations of protein-lipid co oxidation in a food system that contains proteins and lipids as major constituents.
  • Pekkarinen, Antti-Juhani (Helsingin yliopisto, 2018)
    The reindeer (Rangifer tarandus L.) is a key species in Fennoscandia, where nearly 40% of the land area is used as reindeer pasture. Reindeer herding is an important source of income for local people and an intrinsic part of the Sami culture In this thesis, the reindeer herding system is studied using a detailed interdisciplinary dynamic model. An age- and sex-structured reindeer-lichen model is developed using findings from previous research and novel data. The model also takes other winter resources, including supplementary food, into account in addition to ground lichens. This ecological model is combined with economic optimization and a description of the herding system with empirically estimated prices, costs, and governmental subsidies. The model is validated and calibrated to describe the reindeer herding system in the northern part of Finnish Lapland. The results for population dynamics without harvesting show that the reindeer-lichen system described by the model is unstable in the absence of predators. However, high availability of arboreal lichens stabilizes the system. In economically optimal solutions increasing the interest rate increases the steady-state reindeer population level, opposite to classical understanding in resource economics. Natural mortality is close to zero in optimal steady-state solutions and harvesting is concentrated on calves. The number of adult males is kept as low as possible without decreasing the reproduction rate of the population. This leads to much higher shadow values for males compared to females. The results show that in order to study sustainable and economically viable reindeer management, both ecological and economic factors must be taken into account, as they strongly affect the solutions and management recommendations. One of the main findings is that the economically optimal steady-state lichen biomass can be surprisingly low. High interest rate, lack of pasture rotation, low growth rate of ground lichen, high availability of arboreal lichens, and government subsidies all decrease the steady-state lichen biomass. Using intensive supplementary feeding to support larger reindeer herds, which leads to the depletation of lichens, can additionally become optimal in certain cases. When recovering from overgrazed lichen pastures, use of supplementary feeding and the amount of arboreal lichens have an important role in the optimal adaptation process. The wintertime wastages estimated in this study are close to earlier suggestions, but summertime wastage is higher than expected. Seasonal pasture rotation could thus considerably help reduce the summertime trampling of winter pastures. The model validation solutions show that the model is able to describe changes in lichen biomass with good accuracy. Using the validated model and calibrated wastage values we found that reindeer numbers in northernmost Finland in the present situation are in most cases higher than in the management solutions given by the model.
  • Kylkilahti, Eliisa (Helsingin yliopisto, 2018)
    This study approaches service consumption from the viewpoint of socio-cultural consumption studies and participates in the performance theoretical discussion on services. The main interest is to shed more light on the concepts of reflexive consumer agency and cultural positioning with the conceptual tools provided by performance theory and by narrative theory. The study asks, firstly, what sort of cultural meanings are given to the everyday service performances and what sort of resources are embedded in the subject positions of these performances, especially among young people; and, secondly, how the cultural, even routinized, service performances are constructed – changed or reproduced by these differently positioned service actors? The empirical data consists of 356 service stories of either ‘pleasant’ or ‘unpleasant’ service experiences written by Finnish consumers and service workers that accepted the invitation to share their service stories, that is, stories. Sub-samples were analyzed in the articles. The interpretive analyses are based on narrative approach: close reading, dramatism and positioning theory. The findings suggest that service performances are an arena for multiple, overlapping cultural performances. According to the cultural storylines, the young are often positioned as invisible actors or as potential troublemakers. Furthermore, the findings suggest that as the routine service scripts are disrupted and reflexive consumer agency is evoked – for example due to the above mentioned collisions of cultural storylines – service performances may become gameful. The study found that gameful service performances take shape in both co-play and counter-play. Moreover, the study detected tactics that consumers employ in order to (re-)construct the nature of the gameful service performances and, thus, to negotiate their positioning. These consumer tactics make use of situational offerings as the consumers draw cultural and social resources from their everyday life; they include masquerade, co-performance, team building and extension of the service scene. The study argues that disruptions in service scripts provide opportunities for cultural changes initiated by actors that have traditionally been considered powerless in the service context. Consumers should be acknowledged as active and creative developers of cultural scripts, yet, it must be understood that they do not have equal resources to introduce tactical openings. Thus, the study enhances understanding of consumer tactics; consumers can utilize socio-cultural resources in their political endeavors. In addition, the findings of this study support the theory of commercial enculturation; it is worthwhile to enhance the view on young people as active, knowing and competent actors that are not only the consumers of tomorrow, but the consumers of today, as well, as they participate in cultural meaning making ‘here and now’.
  • Bao, Yulong (Helsingin yliopisto, 2018)
    The aim of the thesis was to investigate the effects and mechanisms of protein oxidation on meat quality traits, such as texture, color and water-holding properties. To achieve this, meat was subjected to modified atmosphere packaging (MAP) with different oxygen concentrations and protein oxidation as well as meat quality traits (with a focus on texture and color) were measured. In addition, a model system of HClO-oxidized myofibrils was used to study the effect of protein oxidation on filament net charges, protein aggregation and their relation to water-holding. Generally, protein oxidation was found to increase significantly both with increasing oxygen concentrations in MAP and with increasing concentrations of the oxidant HClO. Lipid oxidation, measured as TBARS, was also greater in meat stored under higher oxygen atmosphere. Shear force of porcine longissimus dorsi (LD) muscle increased with increasing oxygen concentrations demonstrating a meat toughening effect. The role of proteolysis and protein cross-linking on oxidation-induced toughening was investigated. Myosin heavy chain (MHC) cross-linking was greater in 80% oxygen MAP than 0% and 20% oxygen, while desmin degradation was not affected by the oxygen concentrations in MAP, suggesting that oxidation-induced toughening was due to cross-linking of structural proteins rather than reduced proteolysis. Oxidation-induced toughening was also observed in minced beef as the hardness was generally greater in patties made from meat stored under 20-80% oxygen compared to 0% oxygen. The internal redness of cooked patties decreased with increasing cooking temperatures and increasing oxygen concentrations in MAP, and a relative low oxygen concentration of 20% was able to cause premature browning (e.g., the patties made from 20% oxygen packaged meat showed brown cooked appearance at 55 ºC while 0% oxygen led to pink-red color). In the model system, water-holding was generally improved by oxidation. Protein cross-linking was evidenced by increasing particle size with increasing concentrations of HClO. Isoelectric focusing (IEF) showed that the isoelectric point (pI) of solubilized myofibrillar proteins were generally lower following oxidation, indicating an increase of net negative charge. In the thesis, a hypothesis about oxidation-induced changes and their relation to water-holding is proposed: The oxidation-induced increase of net negative charges is due to loss of positively charged histidine residues through protein carbonylation, and water-holding is a balance between promoting factors (e.g., increased net charge) and inhibiting factors (e.g., cross-linking and aggregation).
  • Olascoaga, Beñat (2018)
    Photosynthesis requires a balance between its light-dependent and light-independent reactions so that the energy input through photochemistry matches its consumption. Biochemical and physiological processes help to achieve this balance, as certain processes regulate the activity of light-dependent photochemical reactions, whilst others regulate the activity of temperature-dependent biochemical reactions. Biochemical and physiological processes also modulate the absorbed energy available for photosynthesis by diverting a fraction into non-photochemical pathways that dissipate energy as heat and fluorescence. Interestingly, certain biochemical and physiological processes behind the dynamics of photosynthesis correlate with leaf optical properties (LOPs), which represent an approach to characterising the dynamics of photosynthesis. Yet, how solid is our knowledge concerning the biochemical and physiological processes influencing LOPs, and how accurately do LOPs and the biochemical and physiological processes behind photosynthetic dynamics correlate when investigated across various spatio-temporal scales? This thesis investigated whether reflectance-based and fluorescence-based LOPs adequately correlate with the biochemical and physiological processes behind photosynthetic dynamics, and whether their correlations hold true at various spatio-temporal scales. This thesis demonstrates the validity of reflectance-based and fluorescence-based LOPs as optical proxies for investigating the dynamics of photosynthesis. However, it also identifies sources of variability that cause the correlations between photosynthesis and LOPs to break down. This thesis classifies the sources of variability in terms of methodological (i.e. over-simplification and technical/instrumental constraints) and spatiotemporal limitations. The over-simplification of processes behind the dynamics of photosynthesis and LOPs was addressed by studying the absorption of photosynthetically active radiation (PAR) by conifer needles. PAR absorption is generally considered to be chlorophyll concentration-dependent, yet this thesis shows it to be additionally modulated by the effect that waxes have on needle PAR reflectance. Due to the difficulties of directly measuring needle PAR absorption, PAR reflectance was used as a proxy of PAR absorption. To solve this technical/instrumental constraint, this thesis presents a new methodology that facilitates the direct estimation of PAR absorption. This thesis also demonstrates that certain LOPs appear to be insensitive to detecting the dynamics of certain biochemical and physiological processes over time. This was true for the photochemical reflectance index (PRI), which failed to detect zeaxanthin independent processes behind the thermal dissipation of the absorbed PAR. Lastly, this thesis shows that LOPs can also be influenced by leaf morphology, which could affect the optically-based monitoring of larger-than-leaf scales. Despite the caveats highlighted in this thesis, the potential to monitor the dynamics of photosynthetic activity by optical means is unquestionable, and the results presented here can contribute to reducing uncertainty in the characterisation of photosynthesis by optical means at varying spatio-temporal scales.
  • Koivumäki, Tuuli (Helsingin yliopisto, 2018)
    Milk whey proteins, especially α-lactalbumin and β-lactoglobulin, are valuable to human nutrition due to their excellent amino acid composition. For this reason, they are also favored by sports nutrition industry. In food products, proteins often constitute with a desired technological function, such as their water-binding, foaming and emulsifying properties. Oxidative deterioration of proteins alters these properties, and can occur during processing and storage. Perhaps even more importantly, oxidation of proteins can lead to their compromised bioavailability and loss of nutritive value, if the so called essential amino acid residues are affected. In order to evaluate the oxidation status and quality of food proteins, versatile analytical tools are needed. The currently available methods, also used in milk studies, include a very general spectrophotometric measurement of carbonyl compounds which are typically formed by many oxidation reactions. However, the milk whey proteins are particularly rich in amino acids such as cysteine, methionine, tryptophan and tyrosine, which are all known to produce oxidation products other than carbonyl form. More accurate tools are needed to allow a better fit for the different types of proteins, and to expand the understanding of site-specific oxidation reactions. The purpose of this dissertation study was to establish a novel protocol for the investigation of protein oxidation via peptides produced by trypsin digestion. The proteins used in the study were α-lactalbumin and β-lactoglobulin, the two main ingredients of bovine milk whey. The selected peptides were chosen based on their amino acid composition containing at least one residue known to be oxidatively prone. Fractionation was achieved with a developed preparative-HPLC-MS method, and the collected peptides were oxidized individually in metal-catalyzed oxidation (MCO with Fenton chemistry) conditions for 14 days in +37 °C. Furthermore, LC–ESI-QIT-MSn methods including UV/VIS and fluorescence detectors, were created to investigate the site-specific oxidation modifications in the studied peptides. The results gathered in this study showed that carbonyl formation was often secondary to other amino acid oxidation modifications in the chosen peptides. Only 50% of the included lysine residues were observed to oxidize into the most typical carbonyl form, whereas all of the studied methionine residues as well as most tryptophan and cysteine residues were found to be very prone to oxidize. In addition to the confirmed main target sites of MCO, this study proposes several promising peptides that could be used as markers of oxidation for monitoring the oxidative status of full whey proteins. Especially the proposed peptide markers formed from ALPMHIR and LIVTQTMK of β-lactoglobulin as well as LDQWLCEK and VGINYWLAHK from α-lactalbumin were considered highly potential. In addition, the created and proven analysis protocol provides a valuable basis for further investigations of food protein and peptide oxidation and interaction studies.
  • Ghafar, Abdul (Helsingin yliopisto, 2018)
    Aerogel is a highly porous and lightweight solid material that is prepared by replacing the liquid phase of a gel with air in such a way that the three-dimensional polymeric network remains intact in a dry state. Polysaccharides as aerogel-forming materials have attracted attention over the past few years due to their excellent innate properties, such as their non-toxicity, eco-friendliness, and derivation from renewable resources. Therefore, aerogels from polysaccharides have enormous potential for biomedical, pharmaceutical, and food industrial applications. Formation of the gel is the first step towards the aerogel preparation, though not all polysaccharides tend to form a gel in their native form. It is therefore required to make some modifications to their structures. The choice of modification technique is of the greatest importance in developing polysaccharide-based aerogels for food and food-related applications because the modification technique should be safe. In this thesis, galactose oxidase (GaO) was used as a safe and environmentally friendly modification technique to oxidize and cross-link the polysaccharides guar galactomannan (GM) and tamarind seed xyloglucan (XG). Furthermore, the oxidation ability of GaO and the formation of GM and XG hydrogels were studied in the presence of varying quantities (5–25%) of nanofibrillated cellulose (NFC) as a reinforcing agent to obtain composite hydrogels. The liquid phase of the hydrogels was removed using two different drying techniques: lyophilization and supercritical CO2 (sc-CO2) drying, and the relationship of these techniques to the aerogels’ properties, such as volumetric shrinkage, morphology, specific surface area, and mechanical behavior, were also studied. In this thesis, the synchrotron X-ray microtomography (XMT) technique was used as a modern and non-invasive imaging technique to characterize the aerogels for qualitative and quantitative morphological features in relation to their processing conditions. The enzymatic oxidation of GM and XG with and without NFC-reinforcement allowed for the formation of elastic hydrogels. This study showed that the addition of NFC up to 25% did not hinder the enzymatic activity, and in this way, composite hydrogels were obtained. NFC-reinforcement significantly increased the elastic modulus (Gʹ) as compared to the corresponding plain GM and XG hydrogels, but this effect depended on the type of polysaccharide (GM or XG). Replacing the liquid phase of the hydrogels with solvent also showed the strengthening effect of NFC in relation to the GM hydrogel matrix. NFC reduces the volumetric shrinkage, which is dependent on the type of solvent. The lyophilization drying technique is more efficient in terms of preserving the hydrogel’s original volume when converting to the aerogel, especially as compared to supercritical CO2 drying, which showed significant volumetric shrinkage during the drying process. However, supercritical CO2-dried aerogels displayed mesoporous structures with pores sizes in the range of few nanometers to a few hundred nanometers that resulted in high surface areas up to 330 m2/g of such aerogels. In contrast, lyophilized aerogels displayed different morphologies; for example, the size of the pores ranged from 125 to 250 m, and they exhibited a low surface area (< 10 m2/g). The three-dimensional structures of the studied polysaccharide-based aerogels were successfully visualized. Quantitative data provided a complete range of pore sizes and pore wall thickness distributions that were dependent on the ice-templating methods and NFC reinforcement. In conclusion, this study revealed that the properties of the studied polysaccharide-based composite aerogels depend on processing parameters, the choice of drying techniques, and the addition of a reinforcing agent. The properties of GM- or XG-based aerogels can be tailored to a desired application through the selection of a drying method with carefully controlled processing conditions. XMT proved to be a promising characterization technique for bio-based porous materials for understanding their structural properties in relation to their functional properties.
  • Anturaniemi, Johanna (Helsingin yliopisto, 2018)
    Canine atopic dermatitis (CAD) is a multifactorial disease including genetic predisposition and other predisposing factors like living environment and diet. There is no known cure for this disease. The right and functional treatment can be hard to find, and more effort should be put into the prevention. The aim of this thesis was to find environmental factors and breeds associated with allergic skin symptoms and atopic dermatitis in pet dogs. In addition, the effect of a raw diet on gene expression, physiology and metabolism was studied with clinical diet intervention trial setup, using client-owned dogs. A population of 8643 dogs from the validated DOGRISK questionnaire was used to analyse the environmental factors and dog characteristics related to CAD. Five breeds with the most owner-reported skin symptoms as a percentage within the breed were found to be i) West Highland white terrier, ii) boxer, iii) English bulldog, iv) Dalmatian, and v) French bulldog. When FCI breed groups were compared to mixed-breed dogs, groups 3 (Terriers) and 6 (Scent hounds and related breeds) had a significantly higher risk for owner-reported skin symptoms. On the other hand, groups 5 (Spitz and primitive types) and 10 (Sighthounds) had a significantly lower risk for owner-reported skin symptoms. The environmental factors found significantly associated with less owner-reported skin symptoms and veterinary-verified CAD were i) being born in the owner family and ii) living with other dogs. In addition, significant association of less owner-reported skin symptoms was found with dogs living in a detached house. Factors that were significantly associated with more owner-reported skin symptoms included extremely clean household and over 50 % of white colour in the coat. In the clinical diet intervention study, 46 client-owned atopic and healthy Staffordshire bull terriers were fed two different kind of diets (raw and dry food). Haematological and clinical chemistry profiles, folate, B12, iron, and transforming growth factor β1 (TGF- β1) concentration were analyzed. In addition, gene expression profiles were determined from the skin samples of eight dogs. Cholesterol was significantly increased in the dry food fed dogs and decresed in the raw food fed dogs. In addition, the raw food significantly decreased, among others, alkaline phosphatase and glucose. Plasma folate and B12 and whole blood iron were significantly decreased, and TGF- β1 significantly increased by the raw food diet. The skin gene expression was also affected by the diet. There were genes related to immune defence, reactive oxygen species and antioxidants upregulated in the dogs fed raw food. Several genes were found differentially expressed between atopic and healthy dogs, some unrelated to diet fed and some differentially affected by the diet in atopic and healthy dogs. These results are preliminary and should be confirmed using more samples. Nevertheless, they give an interesting and novel information about the effect of the diet on the skin gene expression. In conclusion, this thesis presents results from different study designs all concentrating on the same disease, canine atopic dermatitis. Many results presented here are related to immune defence and exposure to microbes. Too clean environment and food might not stimulate the immunity enough and could lead to incorrect development of the immune system in young animals. The incomplete stimulation could result in CAD and hypersensitivities later in life, and should be considered when thinking of the prevention of these diseases.