Browsing by Subject "Food Science"

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  • Kamlang-ek, Pimwalee (Helsingfors universitet, 2012)
    The literature survey reviewed principles of oxidation of edible oils, adverse effects of lipid oxidation and analysis of volatile oxidation products by SPME-GC-MS. The main aim of the experimental research was to study the influence of relative humidity (RH) on the release of volatile oxidation products from spray-dried emulsions with natural and cross-linked casein as emulsifier. The release of volatiles was determined by SPME-GC-MS. The sub aims were to study the effects of stabilization time at specific RHs, of temperature and agitation speed during the SPME extraction. The spray-dried emulsions were oxidised at 40oC in order to reach a certain level of oxidation. Next, the powders were stabilised under five RHs (0%, 11%, 33%, 54% and 75%) for one or two weeks in order to observe the effect of the RH and the stabilisation time on the release of volatiles. After adjusting the RHs, volatile compounds were analysed by SPME-GC-MS. The following SPME extraction conditions were tested: C1: temperature 40oC, agitation speed 250 rpm, C2: 50oC, 250 rpm, C3: 40oC, 500 rpm and C4: 50oC, 500 rpm. Identification of the compounds was carried out by matching their MS spectra with the NIST database. Altogether 45 volatiles released from the powders could be identified, and 18 of them were found in most samples. RH had an important effect on the release of volatiles from the encapsulated samples. The highest release was always observed at 11% and 33% RH, whereas the lowest release was found at 0% and/or 75% RH, depending on the SPME extraction conditions. The stabilisation time did not have a significant effect on the release of volatiles in most RHs. During the SPME extraction step, elevation of the temperature from 40oC to 50oC, as well as the agitation speed from 250 rpm to 500 rpm, facilitated higher release. However, the effect of temperature was greater than that of agitation speed. Although it was suspected that cross-linking of sodium-caseinate would enhance retention of volatiles, our experiment showed greater peak areas of most volatiles from the cross-linked samples than from the natural ones. By controlling the SPME parameters, it was possible to obtain repeatable volatile compound results. The SPME-GC-MS method applied in this study can be reliably used to analyse volatile oxidation products from spray-dried emulsions. Only at very low or high RH the release of volatiles may differ from samples stored at 11% -54% RH.
  • Tang, Jingsi (Helsingfors universitet, 2017)
    The literature review illustrated the negative impacts of mold spoilage in baked goods and the significance of lactic acid fermentation used to prevent mold growth, with a special emphasis on the mechanism of antifungal metabolites produced by lactic acid bacteria. A brief introduction of the raw materials (faba bean and pearl millet) was also involved. The aim of this study is to explore the potential of different strains of lactic acid bacteria producing antifungal compounds during faba bean and pearl millet fermentation, to facilitate their application in baked foods with extended shelf-life. Different species of lactic acid bacteria isolated from faba bean and pearl millet in previous studies were used singly as a starter for sourdough fermentation. Antifungal assays were carried out on target molds and selected sourdoughs showing antifungal activity were analyzed to assess the nature of antifungal compounds (e.g. organic acids and proteinaceous compounds). All of the water-soluble extracts from sourdoughs were able to inhibit the growth of the indicator molds P. paneum and P. albocoremium, but not A. niger. This was in agreement with previous findings, showing that sensibility towards different antifungal compounds is not identical across different molds. The concentration of organic acids and the potential proteinaceous nature of the most active extracts was also established. It was hypothesized that the organic acids produced during fermentation can act in synergy with proteinaceous compounds and could contribute to the antifungal activity of faba bean sourdough fermented with L. sakei F1410 and L. mesenteroides I21 and of pearl millet sourdoughs fermented with P. pentosaceus A133 and A1231. Furthermore, small molecular peptides generated possibly through proteolysis of proteins in faba bean sourdough fermented with P. pentosaceus I02 and in pearl millet sourdough fermented with L. palantarum A103 could be responsible for the antifungal effect.
  • Yang, Yingying (Helsingfors universitet, 2013)
    The literature review presented the effects of the polyglutamate chain on the biological and nutritional properties of folates and the main methods used for folate assays, with a special emphasis on the approaches to studying intact polyglutamates. A brief introduction regarding safety aspects of folate fortification was also given. The aim of this study was to develop a UPLC-FLR/PDA method for simultaneous determination of polyglutamyl folate vitamers. Chromatographic conditions were optimised for the resolution of polyglutamyl 5-methyltetrahydrofolates and major naturally-occurring monoglutamates. Method validation was conducted for both the UPLC method and affinity chromatography. Applicability of the validated method was evaluated on lupin flour, faba bean flour, and dry yeast, which were subjected to preparatory treatments with and without deconjugation. In addition, the effects of the sequential modification of preparatory treatments on the folate content and composition were investigated by using both the UPLC method and Lactobacillus rhamnosus assay. A desirable separation of target polyglutamates and monoglutamates was successfully achieved on the BEH C18 UPLC column within 11 minutes. The optimised UPLC method showed satisfactory selectivity, linearity, and sensitivity for the determination of methylated polyglutamates in the femtomole range and monoglutamates in the picogram range. Affinity chromatography showed satisfactory recoveries for polyglutamyl 5-methyltetrahydrofolates, but not for 5-formyl polyglutamates. In all three selected foods, 5-methyltetrahydrofolate was the dominant folate vitamer. Meanwhile, the analysis of undeconjugated samples showed that in the intact methylated folate pools, pentaglutamate predominated in legume flours and heptaglutamate in dry yeast. In addition, different sequences of enzyme and purification pretreatments were found to significantly affect both the total measurable folates and the folate profiles. Our standard preparatory procedures comprising simultaneous treatments with amylase and conjugase, then protease and affinity purification resulted in the greatest yield of total folates, but UPLC analysis indicated incomplete deconjugation. However, a modification in which deconjugation was conducted as the last step enhanced hydrolysis efficiency.
  • Ma, Kaiyue (Helsingin yliopisto, 2019)
    The literature review deals with coeliac disease and wheat, rye and barley prolamins. The characteristics and analysis methods of the prolamins were discussed. Furthermore, the ELISA types, antibodies and reference material in ELISA were introduced in literature review. The aim of this master thesis study was to determine the feasibility of barley C-hordein as reference material in the quantification of wheat gluten in a sandwich ELISA method based on R5 antibody. RP-HPLC was used to determine the compositions of wheat prolamins from 27 wheat cultivars. SDS-PAGE was used for wheat prolamin subgroups identification. The R5 antibody reactivity of prolamins and the same prolamin group from different cultivars were tested. By comparing the R5 reactivity of total gluten of the 27 wheat cultivars, 10% barley C-hordein was used to calibrate the gluten content in spiking test of oat flour and oat biscuits. Omega 1,2-gliadin (Km 13) and γ-gliadin (Km 21) showed rather strong R5 reactivity while ω 5-gliadin (Km 203) and LMW glutenin subunits (Km 523) showed almost no reactivity against R5 antibody. However, the subgroup R5 reactivity differences between cultivars were not significant. The reactivity of total gluten from 27 cultivar varied from Km 14 to 192, with a logarithmic average Km 53. Thus, 10% C-hordein (Km 49) had similar reactivity of the average of all cultivars. In flour spiking test, the recoveries calibrated with PWG gliadin were 57-187%, comparing to 30-115% with 10% C-hordein calibration. In biscuit spiking test, the recoveries calibrated with PWG gliadin and 10% C-hordein were 84-145% and 44-76%.
  • 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.
  • Han, Xiaocui (Helsingin yliopisto, 2018)
    The literature review dealt with the chemical and physical properties of chitin polymer and its degradation product glucosamine. Particular emphasis was given to studies on the analytical methods of determination of chitin from various products including gravimetrical, spectrophotometric and chromatographic methods. The aim of this study was to optimize an analytical method to determine insect chitin and to apply the method to quantify chitin in whole insects and their soluble protein fractions. Two species of insects were selected: mealworm larvae (Tenebrio molitor) and cricket (Acheta domesticus). Whole insects and their protein fractions were treated with alkaline to remove protein. Chitin in de-proteined insect material was then hydrolysed into glucosamine using 6M HCl. Glucosamine from the hydrolysate was determined using chromatographic and spectrophotometric methods, where chromatographic method was optimized and validated. UPLC-FLR method was specific for glucosamine and the UPLC system could separate two target peaks (glucosamine isomers: α and β). Glucosamine content was calculated using a calibration curve which showed excellent linearity in range 0.0033~24.0 ng/inj. with the determination coefficient more than 0.999 during the study period. The instrumental limit of detection and limit of quantification were 0.00095 ng/inj. (2 µL) and 0.0033 ng/inj. (7 µL), indicating a satisfied sensitivity. Recovery of glucosamine spiked to sample matrix (de-proteined cricket flour) following chitin hydrolysis was not satisfactory (~75%) using HPLC-FLR method, which indicated that spectrophotometric method gave chitin amount closer to the true value due to a higher recovery (>90%). Major findings on chitin amount was ~5% on dry matter basis in both mealworm and cricket. A small percentage of chitin was found in insect protein fractions extracted by 0.1M NaCl.
  • 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.
  • Wang, Cong (Helsingfors universitet, 2016)
    Recently, an unknown myopathy has been observed in some Finnish broiler Pectoralis major muscle for the past 3 years and similar breast muscle defect have been found in several other countries as well. Wooden Breast is the term to describe this abnormality due to its macroscopically visible hard, bulging and pale area in the caudal part of the fillet. This study aims to compare and measure some physical properties and chemical composition differences between Wooden Breast and Normal broiler breast muscle. 32 breast fillets of 38 days old Rose 508 broilers were sacrificed at the university experiment premises for evaluation. 20 breasts muscle were Wooden Breast affected, and the other 12 macroscopically Normal breast muscles served as Normal. In this experiment, measurement of sample physical properties (drip loss, cook loss, compression test, and Allo-Kramer shear force) and chemical composition (moisture, protein, and collagen content) were conducted. As for the results, Wooden Breast had lower protein content and higher moisture content (P<0.05) than Normal; Wooden Breast had higher drip and cooking losses (P<0.05) than Normal; Wooden and Normal breast muscles did not differ in the initial and the ultimate pH; Wooden Breasts had similar compression (24h) and shear force (cooked) results compared to Normal breast (P>0.05); No quantitative difference in total or soluble collagen were detected (P>0.05).
  • Karpik, Elena (Helsingin yliopisto, 2020)
    In general the amount of fat in cow’s milk, what consists mostly of fatty acids, is about 4%, and more than half of the milk fatty acids are saturated. Dairy fat, due to its saturated fat and cholesterol content, is related to the risk of cardiovascular disease. Moreover, energy from fat can also be related to obesity. These relations also concern cow’s milk, however, its fat content remains around 4% and besides fat, there are a lot of positive effects on health, as milk is a good source of some vitamins and minerals. Milk consumption in Finland per capita has been the largest in the world for many years. There is also a market for milk substitutes, i.e. non-dairy drinks, produced mostly from oat, soy, and almond. This master’s thesis focuses on cow’s milk fat content and its relations to human health, especially the cardiovascular health and obesity. According to the hypothesis, consumer attitude towards cow’s milk is strongly affected by assumptions associated with the impact of dairy fat on health as well as the impact of dairy industry on climate change. The aim of this research was to study how detrimental or beneficial the dairy fat in milk is for human health on the basis of cow’s milk chemical composition, health related reports by authorities, research findings, historical perspectives, and consumer preferences. According to the literature, the chemical composition and nutrients properties of whole milk show that more nutrients of health benefit are present in comparison than of detrimental compounds. Most of present evidence suggest that milk and dairy products have neutral or beneficial effect on human cardiovascular health alhtough it is generally recognized in dietary recommendations that saturated fat is a risk factor for cardiovascular disease. The experimental part investigated Finnish consumers attitudes and preferences regarding milk consumption and overall preferences and issues affecting attitude toward food choice. It appears that the study hypothesis partly refuted, as the majority of participants were not much affected by assumptions associated with the impact of dairy fat on health. However, the impact of dairy industry on climate change was a very important issue related to attitude and preference regarding milk consumption. The majority of the study participants made their choice of drinking milk on the basis of taste, and the impact on health was considered mainly as beneficial rather than detrimental.
  • Zhang, Yiling (Helsingin yliopisto, 2014)
    Oat protein is a valuable cereal protein with high protein content and a good balance of amino acids profile. However, the inflexible molecular structure and poor watersolubility of oat protein limit its application in food industry. To exploit the food use of oat, the functionalities of oat proteins should be improved. ?-chymotrypsin, a proteolytic enzyme, has been proven as being able to deamidate some food proteins without severe hydrolysis under alkaline pH conditions, hence to improve the protein functionalities. The aim of this research was to test whether oat protein could be deamidated by ?- chymotrypsin under alkaline pH conditions. The extent of ?-chymotrypsin-induced proteolysis on oat protein was also studied. Oat protein was treated by ?-chymotrypsin under alkaline conditions from pH 8 to 11 at room temperature for 2 hours. The deamidation degrees of the proteins were measured by ammonia quantification. The hydrolysis degrees of proteins were analyzed by trichloroacetic acid precipitation and protein quantification method. The changes of molecular weights were analyzed by SDS-PAGE and SE-HPLC. The action of ?-chymotrypsin under alkaline pH conditions induced slight deamidation of oat protein to low deamidation degrees (9-12%). On the other hand, ?-chymotrypsin mainly caused hydrolysis of oat protein to hydrolysis degrees between 49% and 62%. SDS-PAGE and SE-HPLC analysis also revealed that significant hydrolysis of oat protein occurred during the reaction. The hydrolysis mainly caused the shift of oat protein fractions from molecular weight above 20 kDa to molecular weight below 15 kDa. Change in pH did not cause significant differences on deamidation degrees and hydrolysis degrees of oat protein In conclusion, oat protein could not be effectively deamidated by ?-chymotrypsin under alkaline pH conditions, while the proteolysis was severe.
  • Song, Yue (Helsingin yliopisto, 2018)
    Highly glycemic index of wheat bread causes rapid increase of blood glucose level which is harmful for people with chronic diseases such as type II diabetes and obesity. Consumption of whole grain bread rather than bread from refined wheat flour is an alternative way to reduce the risk of chronic disease. In Africa, the occurrence of chronic diseases is on the rise and therefore alternative products based on whole grain flour are needed. Furthermore, due to climate change the smart solution would be to utilize flour from cereal grains that are produced locally rather than being imported. Fonio is one of the oldest cereal in West Africa. Gluten-free fonio is always consumed as whole grain flour which is beneficial for digestion and cardiovascular function. Sourdough fermentation is known as a processing that can influence starch and protein digestibility in bread making. Moreover, sourdough is needed to enhance the quality of whole grain fonio bread. Utilization of sourdough fermentation is a potential method to improve the texture, sensory and nutritional qualities of bread. The aim of this thesis work is to evaluate the protein and starch digestibility of wheat bread with 40% whole grain fonio sourdough. In this study, breads were prepared and used for protein and starch digestibility studies. Freeze-dried samples were used for total starch and protein contents analysis. Moisture content of the breads was also analyzed to calculate the weight of samples needed for in vitro starch and protein digestibility. Pancreatic amylase was used to determine the starch in vitro digestibility. Breads with 1g starch were incubated at 37℃ with continuously shaking after which the reducing sugar content was determined. Glycemic index was calculated based on the starch hydrolysis percent. Protein in vitro digestibility was measured by pepsin and pancreatin. Breads were incubated at 37℃ with constantly shaking. The un-digested protein was determined by Dumas method. The protein digestibility was calculated with the total protein content. Phytate content was tested by the phytate content kit from Megazyme. Compared to wheat bread, fonio breads all had lower starch digestibility. This phenomenon was mainly caused by the wholegrain which increases the content of dietary fiber and enzyme inhibitors. For sourdough bread, there was a slight decrease of starch hydrolysis percent compared to control fonio bread. Sourdough enhanced the solubility of dietary fiber which therefore increased viscosity of chyme. Higher viscosity of chyme affects the glucose uptake and enzyme contact which consequently contributed to reduction of starch digestibility. Furthermore, the produced organic acids especially acetic acid may contribute to the lower starch digestibility of sourdough bread. Glycemic index of sourdough fonio bread was the lowest one among all the bread samples. For protein digestibility, fonio breads all had lower protein digestibility compared to wheat bread. However, there was an increase of protein digestibility by sourdough fonio bread. LAB protein metabolism to get enough nitrogen resources may explain this. The lower content of phytate in sourdough fonio bread may also influence the protein digestibility. In conclusion, sourdough fonio bread has lower starch digestibility than wheat bread and can enhance protein digestibility compared to fonio bread without sourdough.
  • Sundarrajan, Lakshminarasimhan (Helsingfors universitet, 2014)
    Amaranth, quinoa, kañiwa and lupine are good sources of protein, fat, dietary fibre and bioactive compounds. The literature review deals with the nutritional properties and the stability of bioactive compounds and the effect of extrusion cooking on amaranth, quinoa, kañiwa and lupine. The main aim of this study was to (1) chemically characterize amaranth, quinoa, kañiwa and lupine, and (2) to determine the effect of extrusion cooking on the nutritional properties and the stability of bioactive compounds. Extrudates were processed using twin screw extruder at two different extrusion temperatures (140 and 160 °C) containing two different contents of tested flour mixtures (20 and 50%). The raw materials and the extrudates were stored at -18 °C and chemically characterized to determine fatty acid composition, tocopherol composition and total phenolic acid content. Fatty acid composition was determined using GC while tocopherol composition was detected using HPLC. The total phenolic acid content was analyzed using Folin-Ciocalteu method. The protein and dietary fibre content in lupine accounted for 29 and 50 g/100 g d.m., respectively. The extrudates containing 50% lupine and processed at 140 °C possessed higher content of oleic, linoleic and linolenic fatty acids. At higher content of tested flours, extrusion cooking at 160 °C resulted in better retention of unsaturated fatty acids in the extrudates of amaranth, kañiwa and quinoa. Higher extrusion temperatures resulted in lower retention of tocopherols in all the extrudates. The total phenolic acid resulted in higher contents in the extrudates of kañiwa when compared to other extrudates. At higher seed contents of tested flours (%), higher retention of total phenolic acid was achieved during extrusion cooking at 140 °C in the extrudates of amaranth, quinoa and kañiwa. This study showed that extrusion conditions could be optimized in order to obtain lesser effects on the nutritional properties and better retention of bioactive compounds. The research study provides supportive information for obtaining gluten-free cereal snack products with lower glycemic index.
  • Gabucan, Ma.Heidi (Helsingin yliopisto, 2020)
    The literature review highlighted the principles of microencapsulation and spray drying, with emphasis on the properties of highly oxidizing oils, protein interface modification, and mechanism of lipid oxidation. The major aim of the research was to study the chemical and physical stability of microencapsulated flaxseed oil (MFSO) during storage under controlled relative humidity conditions (0%, 11%, 33%, 54%, and 75%RHs) and compare the results to bulk flaxseed oil (FSO). Microencapsulation was done by spray drying of non-cross linked (NCL) and transglutaminase cross-linked (CL) Na-caseinate FSO emulsions. Oxidative stability was examined through changes in physical and chemical properties of MFSOs and FSO as influenced by different RHs and storage periods. Chemical analyses were used to analyze the peroxide value (PV), fatty acid profile, γ-tocopherol, carotenoid and chlorophyll, phenolic compounds, and secondary oxidation products (hexanal and propanal) in MFSOs and FSO. Degree of secondary oxidation was determined by static headspace gas chromatography while the morphology of MFSOs was examined by scanning electron microscopy. Results showed that at dry condition (0%RH), surface lipids of CL and NCL MFSOs were unstable and more susceptible to oxidation after 17 weeks storage. Release of hexanal and propanal were higher for NCL than CL microencapsulated flaxseed oil which suggested that interfacial cross-linking of Na-caseinate was efficient. At high moisture condition (75%RH), MFSOs were oxidatively stable owing to their low PVs and structural transformation from porous structure to agglomerates or sticky form. High amounts of alpha-linolenic acid and γ-tocopherol were detected in FSO and MFSOs, and only minor losses occurred throughout storage period and under different RHs. FSO also contained considerable amounts of carotenoid and phenolic compounds but low in chlorophyll content. Oxidative stability of interface and matrix elucidated that humidity conditions considerably influenced the chemical and physical properties of CL and NCL MFSOs.
  • Dominguez-Hernandez, Elisa (Helsingin yliopisto, 2015)
    The aim of this project was to study the physical and chemical changes in the myofibrillar protein fraction during low-temperature long-time (LTLT) heat treatment of pork, in relation to cathepsin activity and evolution of tenderness. Porcine Longissimus dorsi muscles were cut, vacuum packaged and cooked in water baths at 53, 58, 63, 68 and 73°C. The process was monitored at: 1, 8 and 24h. Allo-Kramer shear force (AKSF), residual activity of cathepsin B+L, surface hydrophobicity (SH) and particle size of myofibrils were measured. Results showed that toughness decreased markedly between 53°C and 63°C and later increased to 73°C. Toughness also decreased with time. Myofibrillar SH, increased with temperature, but not with time, indicating aggregation and/or gelation. Treatments with low AKSF had smaller particles, suggesting that meat was easier to break, both macroscopically and microscopically. The high associated catheptic activity could be the reason for the weakening of myofibrils. They also might be able to prevent their aggregation and transition into a hard compact gel. As temperature increases, denaturation-aggregation-gelation overcomes proteolysis and bigger particles were detected. In conclusion, LTLT sous-vide cooking (53 and 63°C) allows the control of short term changes in myofibrils (so they do not toughen) and permits the slow ones (proteolysis) to decrease toughness of prime cuts.
  • Alam, Syed Ariful (Helsingfors universitet, 2012)
    Oats are a good source of protein and dietary fibre, especially ?-glucan. Due to the health benefits of ?-glucan, oats have gained popularity in snack food formulations. The literature review deals with oats and its components, removal of lipids and fractionation of oat products. The particular emphasis of the literature review was given to studies on the effects of different oat fractions and extrusion process variables on the properties of oat-containing extrudates. The aim of this study was to find out how different oat fractions and extrusion process variables (screw speed, water content and feed rate) affect the physical and chemical properties of the extrudates. The measured physical properties were expansion, hardness and water content. Extrusion trials were carried out by using defatted oat endosperm flour (EF) as the main ingredient. Whole grain oat flour (WF) was used as a reference. To improve the nutritional quality, defatted oat protein concentrate (PC) and defatted oat bran concentrate (OBC) were added to EF. The oat fractions were defatted by supercritical carbon dioxide (SC-CO2). Pregelatinised corn starch (CS) and waxy corn starch (WS) were added in some trials to increase the expansion of the extrudates. A co-rotating twin-screw extruder was used for the extrusion. Different process variables were: water content of the mass (16, 18 and 20%), screw speed (240, 370 and 500 rpm) and feed rate (68, 76 and 84 g/min). The temperature profile of the extruder barrel was held constant in all of the trials: 40, 70, 70, 100, 110, 130 and 130 °C (sections 1 6 and die). Screw speed had significant effect on the expansion and hardness. Expansion increased and hardness decreased with increasing screw speed. Water content of the mass affected all the response variables in WF extrudates and all but not hardness and torque in EF extrudates. Increased water content of mass decreased the expansion and hardness in WF extrudates. Feed rate did not have significant effect on the physical properties. When using EF, more expanded and less hard extrudates compared to the WF were obtained. Addition of PC or OBC (10%) decreased the expansion and increased the hardness. Mixing of EF with corn starch (CS or WS; 30%) gave less hard and more expanded extrudates compared to pure EF. The highest expansion was achieved by the addition of WS. Even addition of OBC (20%) in a presence of WS (30%) gave highly expanded and less hard extrudates with high ?-glucan content 7.4% (dry weight). Decreasing the particle size of OBC (by ultra-fine milling) or the molecular weight of ?-glucan (by enzymatic hydrolysis) did not affect the physical properties of the extrudates even though small decrease in hardness was observed in the trial with enzyme-hydrolysed OBC. The results showed that defatted oat fractions can successfully be used in extrusion when mixed with corn starch. Screw speed had the most profound effect on the physical properties of the oat-containing extrudates followed by the water content of mass.
  • Wei, Wei (Helsingin yliopisto, 2020)
    The literature review deals with the status and the causes of bread waste all over the world. More importantly, the current managements of increasing bread waste. Enzymatic hydrolysis by α-amylase and amyloglucosidase is a potential treatment, which transforms bread waste into syrups for further revaluation with functional compounds. The aim of the experimental work was to determine the influence of enzymatic hydrolysis conditions (hydrolysis time, hydrolysis temperature, enzyme dosage of α-amylase and amyloglucosidase) on glucose content and free amino nitrogen (FAN) content of resulting hydrolysate from bread waste. Furthermore, the effect of lactic acid fermentation on glucose content was studied when bread waste was subjected to simultaneous hydrolysis and fermentation with Pediococcusclaussenii (E-032355T). Glucose content varied greatly under different hydrolysis conditions from nearly 17% to only 5%, while FAN content was barely influenced. pH value had slight changes and no Bacillus cereus bacteria was found. A well fitted model for glucose content was obtained with an excellent power of interpretation, prediction and optimization. Enzyme dosage was the principal factor having a significant effect on hydrolysis efficiency, followed by temperature and time. With optimized hydrolysis conditions (50 mg/kg α-amylase and 2500 mg/kg amyloglucosidase, 30℃, 19 hours), the glucose content 16.31% was achieved, and the result was in accordance with the value 16.39% predicted by the model. Moreover, a 2.2% increase of glucose yield was detected when waste bread was subjected to simultaneous hydrolysis and fermentation compared to the control sample (bread waste was treated only with hydrolysis under the same condition). The well growth of used lactic acid bacteria (LAB) strains Pediococcusclaussenii (E-032355T) resulted in lower pH, which further improved enzymes activities and increased glucose content of the hydrolysate.
  • Sun, Yuting (Helsingfors universitet, 2015)
    Cereal β-glucan is a water-soluble cell wall polysaccharide, which has positive health effects on humans. Oxidative Degradation of β-glucan may occur during food processing, leading to the loss in physiological functionality of β-glucan. Oxidative degradation can result in cleavages of polysaccharide chain, the formation of oxidised functional groups (e.g. carbonyls) along the chain or the release of carboxylic acids (e.g. formic acid). In the case of β-glucan, chain scission and the formation of oxidised functional groups due to hydroxyl-radical induced oxidation has been shown, but the identification of released carboxylic acids has not been done. The aim was therefore to study the oxidation pathway of β-glucan, by analysing its degradation products. The focus was the release of carboxylic acids, especially formic acid. The change in molecular structure of β-glucan after the release of formic acid was also analysed. Barley β-glucan water solutions were oxidised with H2O2 and ascorbic acid at different concentrations (5, 10, 40, 70 mM), in the presence of 1 mM FeSO4·7H2O. Samples were collected on 1, 2 and 4 days and formic acid was analysed using formic acid assay kit. To evaluate the structure of oxidised β-glucan, part of the samples underwent reduction to convert any carbonyl groups back to hydroxyl groups. The oligosaccharide composition and monosaccharide composition of samples were then analysed. Results showed that formic acid was formed in H2O2 treated β-glucan and its content was positively correlated with H2O2 concentration in the presence of Fe2+. Formic acid was also formed in ascorbic acid treated β-glucan but an obvious increase in formic acid content at increased ascorbic acid concentration was not observed. Formic acid accumulated in β-glucan solution over time. Monosaccharide composition showed that samples were mainly composed of glucose. In H2O2 treated β-glucan, however, an additional component was observed which was identified to be arabinose. Arabinose was reduced by reducing agent, indicating that arabinose was formed at the reducing end of oxidised β-glucan. The content of arabinose increased with increasing H2O2 concentration, which was concomitant with a decreasing glucose content. Arabinose content decreased from oxidation day 1 to day 4. Oxidative degradation of β-glucan is proposed to proceed progressively, with random chain scission and degradation of the reducing ends. Formic acid was released due to oxidation and arabinose was formed at the reducing end. As oxidation proceeded, we suggest that the reducing end unit was degraded stepwise to release formic acid. Formic acid is demonstrated to be the oxidation product of β-glucan for the first time. The released formic acid was well related to the degree of oxidation induced by H2O2 and Fe2+. Therefore, formic acid can be used as an indicator for the oxidation of β-glucan induced by H2O2 and Fe2+.
  • Hendrik, Nathaniel James (Helsingin yliopisto, 2017)
    Cocoa butter (CB) is the predominant continuous phase in chocolate systems and has a significant impact on the macroscopic properties of the end product. Conventional methods such as differential scanning calorimetry (DSC), pulsed nuclear magnetic resonance (pNMR), X-ray diffraction (XRD) and polarized light microscopy (PLM) have been used to study CB crystallization primarily in bulk. Potential of alternative techniques to study crystallization such as Raman spectroscopy and Fourier Transform infrared spectroscopy (FTIR) has been explored. The main objective of this thesis research was to study the feasibility of both conventional and alternative techniques to study CB crystallization in different matrices and in tempered conditions. Bulk fat (CB with 1%, 5% or without lecithin), suspensions (CB with 1% lecithin (on fat basis) and sucrose or inulin) and chocolates were sampled as such (non-tempered systems) subjected to a laboratory scale tempering procedure to produce tempered systems. Both non-tempered and tempered products were subjected to DSC, NMR, XRD, PLM, Raman spectroscopy, FTIR and diffusing wave spectroscopy (DWS), in which primary crystallization was monitored or long-term storage was assessed. A toolbox was developed comprising feasibility of complementary techniques and, moreover, the toolbox was used to study the effect of lecithin and bulking materials on the CB crystallization behavior. The tempering procedure was successfully validated for every sample, as proven by the melting profile at 6 hours through DSC. The determination of the solid fat content (SFC) from the raw free induction decay signal by NMR showed to be more useful than the scripted SFC, especially for bulk fat systems. XRD showed its feasibility to study fat polymorphism for both bulk matrices and suspensions, except when sucrose is present, due to its interference in short spacings. PLM could only be used for non-tempered bulk fat systems since in other systems sample preparation cannot be standardized to measure crystallinity. FTIR and Raman spectroscopy seemed to be useful complementary techniques and capable of differentiating polymorphic forms, as is also possible using XRD. DWS showed to be comparable with DSC with an additional improved deconvolution of crystallization peaks. This study resulted in a feasibility toolbox and was used to study the effect of lecithin concentration and bulking materials, where the addition of 1% lecithin concentration in bulk fat and usage of inulin in model suspensions improves the crystallization of the CB matrix.
  • Basnet, Subash (Helsingfors universitet, 2017)
    The literature review of this thesis was focused on the pathway of folate biosynthesis with enzymes involved in it and factors effecting the synthesis of folate by bacteria. The literature was also partly focused on the introduction to propionic acid bacteria (PAB) and the folate production by these bacteria. The aim of the experimental part of the thesis was to screen the folate productivity of selected PAB strains isolated from various dairy and cereal sources after 96-hours anaerobic fermentation and also to see the effect of precursor (para-aminobenzoic acid) of folate biosynthesis on folate production by the strains. Then to further investigate the folate production of some promising PAB strains from screening part either with glucose or lactate as carbon source at four growth phases in aerobic fermentation. The propionic agar medium was used with either glucose or lactate as carbon source in the medium. Optical densities, pH, cell masses were measured after fermentation and folate produced by the strains was determined from biomass and supernatant of the samples using microbiological assay. Carbon consumption and metabolic end-products were analysed with HPLC after fermentation. Some of the screened PAB strains were promising folate producers. Strain 257 produced folate up to 124 µg/l which is even higher than production by some good Lactic acid bacteria (LAB). PAB strains produced intracellular folate upto 28954 ng/g cell biomass and excreted folate into medium upto 107 ng/ml. Strains grew faster with lactate than glucose but cell masses were higher with glucose than lactate even in the low pH. PAB strains showed the highest folate productivity in anaerobic fermentation with lactate as carbon source and aerobic fermentation with lactate as source was observed to be the best for high organic acid production. However, further studies are needed to optimise the cultivation condition of selected PAB strains for their best folate production in different matrices.
  • Wang, Changyin (Helsingfors universitet, 2017)
    Faba bean (Vicia faba L.) is a widely-cultivated legume with high nutritional value, especially rich in protein. However, the presence of antinutitional factors (e.g. phytic acid, condensed tannins, vicine and convicine and others) are hindering its utilization. Lactic acid fermentation is widely applied in food production and it is closely related with the promotion of nutritional, technological and health properties of the fermented food. The aim of this master’s thesis was to explore several functional characteristics of 28 lactic acid bacteria previously isolated from Italian and Finnish faba bean sourdoughs. In this study, phytase activity, β-glucosidase activity and the effect on degradation of condensed tannins, which are potentially directed towards reduction of anti-nutritional factors, were investigated. Three peptidase activities and dextran production capacity of the isolates were also evaluated. Besides, six antibiotics were used to study antibiotic susceptibility among the strains. Leuconostoc mesenteroides I01 and Pediococcus pentosaceus I214 expressed the highest phytase activity while P. pentosaceus I02, F01, F213 had the highest β-glucosidase activity. P. pentosaceus F15 was the most effective to decrease condensed tannins. Among analyzed peptidases, PepL showed the highest activity, especially in Pediococcus strains. High dextran production capacity was observed among isolates of Weissella spp. The strains showing functional traits could be used as starter to improve the nutritional and technological properties of faba bean. Further investigation is still ongoing to evaluate other properties of these lactic acid bacteria as functional starter cultures for faba bean and legume fermentation.