Browsing by discipline "Food Science"

Cereal β-glucan, or (1→3)(1→4)-β-D-glucan, has unique viscous and gelling properties, which are related to its physiological effects. The increased viscosity in human gastrointestinal tract by β-glucan is considered a key factor for its health benefits. However, the possible gelling ability of β-glucan in human intestine and its relation to the physiological functionality have not been investigated. The aims of this study were to investigate the possible structure formation of β-glucan at physiological conditions and to understand gelation difference between oat and barley β-glucan (OBG and BBG, respectively). Additionally, the effects of phytate and molecular weight (MW) on structure formation of β-glucan were studied. Oat (ROBG14, ROBG22) and barley bran concentrates (RBBG18) were used for in vitro studies in upper gut model. OBG14 was extracted from oat concentrates and used for further producing phytate-removed OBG (PR-OBG) or enzymatically degraded OBG (ENZ-OBG). The effect of phytate or molecular weight on gelation of beta-glucan was studied by comparing the gelation of PR-OBG or ENZ-OBG to OBG14 after 2 h and 1 d. The effect of β-glucan source was studied with medium viscosity oat (MOBG) and barley (MBBG) β-glucan with same molecular weight and concentration on day 1 and day 4. The extracted samples were first dissolved at physiological T 37°C for 2 h and the gel properties of the samples were measured with oscillatory measurements. OBG showed more structure formation than BBG at low concentrations in both studies with in vitro digestion model and extracted β-glucan samples at physiological temperature. In vitro RBBG18 (β-glucan content of the in vitro extract 0.6%) showed liquid-like behavior and no hysteresis obtained, indicating no structure formation. ROBG14 (β-glucan content 0.5%) and ROBG22 (β-glucan content 0.6%) showed entangled network, with similar crossover frequencies, 0.07 and 0.1 Hz, respectively. 1.5% MOBG showed liquid-like behavior on day 1, but storage modulus (G’) increased during storage. The undissolved particles in watery medium of MBBG indicated 37°C was not enough for partial dissolution which could lead to gel. At the same concentration (1%), both PR-OBG and OBG14 showed weak gel structure, with slightly higher G’ in PR-OBG. This indicated that phytate is not the reason for better gelation of OBG than BBG, which was hypothesized due to higher residual phytate in OBG than BBG. ENZ-OBG (0.7%) had lower G’ than OBG14 (0.7%), which indicated more structure formed in higher MW OBG at 2 h. To conclude, OBG is more prone to structure formation than BBG at physiological conditions. Phytate was not the reason for better gelation of OBG than BBG.

Saccharomyces cerevisiae var. boulardii is a probiotic strain of the baker’s yeast Saccharomyces cerevisiae. It has a long history of use in treating and preventing several kinds of diarrhea in human. Recently, scientists have drawn their attentions to use this probiotic yeast as a living drug delivery vehicle to the gastric intestinal tract (GIT). Several distinctive features of S. boulardii such as an optimal growth temperature at 37 ºC and better acidic tolerance enable active recombinant protein expression in harsh conditions. Human intrinsic factor (IF) is a glycoprotein secreted by gastric parietal cells and belongs to vitamin B12 (Cobalamin, Cbl) transport family. The gastric IF gene (GIF) encodes this protein. It is an essential protein for the proper absorption of Cbl in the terminal ileum, lacking of which results in vitamin B12 deficiency, especially common among the elders. This study aims to express active human IF from probiotic S. boulardii that can be combined with vitamin B12 forming B12/IF complex and absorbed by intestinal cells. To achieve these goals, a plasmid pSF-TEF1-TPI1-Blast-GIF was designed for S. boulardii transformation. Verification of recombinant IF was accomplished by SDS-PAGE, Western blotting and peptide sequence mapping by mass spectrometry (MS). Experimental results indicated that the recombinant IF was not able to be synthesized in useful amount from S. boulardii using plasmid pSF-TEF1-TPI1-Blast-GIF. Transformation of the plasmid carrying GIF sequence brought significant phenotypic and metabolic modification to the host cells. PCR technique was found unsuccessful to verify the presence of correct plasmid, leaving uncertainty whether the correct plasmid was present in the transformants or not. Interestingly, an immunreoactive band at expected size (45 kDa) could be detected with rat polyclonal antibody in Western blotting. This band could be only detected from the supernatant when cells were grown with Cbl supplement, but shown to be exo-1,3-β-glucanase in MS protein sequencing. However, it is still possible that trace amount of recombinant IFs are secreted but cannot be detected due to MS sequencing limitations. Even though there was a contradictory result in Western blotting compared to that of MS sequencing, the excessive secretion of the exo-1,3-β-glucanase which may corrode yeast cell walls, may explain the different phenotype of transformants in comparison to host cells. This study indicated that not all genetic manipulation tools designed for S. cerevisiae are without problems for S. boulardii. More studies need to be carried out for successful heterologous IF protein expression with this probiotic yeast.

Studies have consistently shown that regular consumption of wholegrain or cereal dietary fibre can prevent and reduce risk of chronic diseases. Despite the extensive worldwide efforts to encourage wholegrain consumption, most cereals in Africa are still mainly consumed in their refined form. Ogi-porridge, which is a traditional fermented cereal based food, for example, serves as a vital source of energy for infants and adults in west Africa, but its nutritional quality is low, particularly in dietary fibre and protein contents. Unfortunately, poor nutrition quality and in some cases microbiologically unsafe fermented foods in Africa not only lead to gastrointestinal disorders, but also contributes to the development of chronic diseases, with long term consumption. Therefore, improving the safety and nutritional quality of cereal-based fermented foods and increasing their dietary fibre content would be an essential step towards reducing the occurrence of these diseases in Africa. This study aimed at evaluating the use of starter cultures, pearl millet wholegrain flour and egusi to improve safety and nutritional quality of pearl millet ogi-porridge. The traditional ogi was prepared in a process that involved soaking, wet-milling, wet-sieving and spontaneous fermentation. Modified ogi was prepared by inoculating pearl millet wholegrain flour (0.5 mm) with Lactobacillus plantarum (previously isolated from pearl millet) and Saccharomyces cerevisiae. Changes in cell density of microbial groups and acidity was followed during production of ogi. Ogi-porridge was prepared from each type of ogi, by adding boiling water to ogi, with minimal stirring. Proximate composition and bioavailability of starch and protein were analyzed for the ogi-porridges. Finally, sensory quality of the traditional and modified ogi-porridges and their egusi milk supplemented forms, were compared by west Africans living in Finland who were familiar with ogi-porridge. At the end of ogi production, only a slight reduction in Enterobacteriaceae cell density was observed in the traditional ogi, while, 2 log cycle reduction in Enterobacteriaceae was obtained for modified ogi. Modified ogi contained 60% higher total titratable acidity than traditional ogi. In the case of nutritional quality, modified ogi-porridge had 10.09% higher protein content than the traditional ogi-porridge. Starch and protein digestibility were also higher for modified ogi-porridge. Sensory evaluation indicated that an organoleptically acceptable ogi-porridge can be prepared from pearl millet wholegrain flour and starter cultures. Supplementation of traditional and modified ogi-porridges with up to 25% egusi milk (8.81% protein content) was acceptable. As percentage of egusi milk increased from 0-25%, protein content of supplemented ogi-porridges increased. In conclusion, a microbiologically safer, nutritionally superior, and an acceptable ogi-porridge was obtained using the modified method of ogi-porridge production employed in this study.

Wooden Breast is a myopathy seen on chicken breast muscles in the last years, causing economic losses. It is associated with hardness and paleness of the muscle, necrosis, fibrosis and macrophage infiltration. The aim of this study was to investigate the differences in sarcomere length and tensile strength between normal and Wooden Breast in chicken. For the sarcomere length measurements 20 unaffected chicken breasts and 21 Wooden Breasts were used. For half of each group electrical stimulation was applied. Sarcomere length was measured in four different locations of each breast: cranial and medial area, surface and depth. The tensile test experiment involved three experimental groups, with 20 samples for each group: unaffected, with focal lesion and with diffuse lesion. Samples were cut from the surface layer of cranial and medial area of every chicken breast, both on longitudinal and transversal direction of the muscle fibers. Results showed that Wooden Breast syndrome has a significant effect on sarcomere length, leading to increased lengths in the affected muscles compared with the normal muscles (p<0.05). There was less lengthening of the sarcomere as result of electrical stimulation in WB muscles compared with normal chicken breasts (p<0.05). The difference in sarcomere length between WB and Normal was smaller in the surface layer of the muscle in comparison with the depth layer. There were no significant difference between the mean values of tensile strength in Normal samples and Focal WB samples, but significantly higher values in Diffuse WB samples (p<0.0001). The Diffuse samples yielded significant higher tensile strength when they were stretched parallel with muscle fiber direction, compared with cross-sectional direction of stretching (p<0.05). In the Diffuse cases the cranial area had increased tensile strength compared with the medial area, indicating an increased level of WB severity in the cranial area compared with medial area.

The literature review deals with faba bean and the important effects of lactic acid bacteria (LAB) fermentation on legumes. Particularly, the information about sourdough and LAB microbiota together with the main factors affecting sourdough microbial community is presented. A brief introduction regarding the methods used for LAB identification is also given. The main aim of the experimental study was to identify LAB microbiota in faba bean sourdoughs of two different varieties during backslopping procedure. Doughs from Italian (I) and Finnish (F) faba bean flours were spontaneously fermented and propagated daily through backslopping on a laboratory scale for 14 days. Samples were taken from selected propagation times (0, 1, 2, 5, 7, and 14) for microbiological and biochemical analyses. The pH values and total titratable acidity (TTA) were monitored throughout the process. Analyses of organic acids and oligosaccharides of selected samples were carried out with HPLC methods at University of Bari, Italy. The identity of the LAB isolates was revealed by sequence analysis of 16S rDNA and the differentiation of LAB strains was analyzed by randomly amplified polymorphic DNA (RAPD)-PCR. Minor changes occurred between I and F sourdoughs based on microbiological and biochemical analyses. However, several differences were found in LAB diversity between these two sourdoughs. More variety of LAB species and higher strains diversity were found in F faba bean sourdough. Besides Pediococcus pentosaceus, Leuconostoc mesenteroides, and Weissella koreensis identified in both sourdoughs, Enterococcus casseliflavus, Enterococcus faecium, Lactobacillus sakei, Lactococcus lactis, and Weissella cibaria were only detected in F sourdough. In both sourdoughs, Pediococcus pentosaceus was predominant and persistent. Also, Leuconostoc mesenteroides was found as second frequent species in both sourdoughs. According to all analyses, the maturity of sourdoughs was achieved during 5 days of propagation. This study demonstrated the importance of flour type and composition on establishing microbial ecology of sourdough. The research study encourages exploring the potential of faba bean flour in sourdough-type fermentation and encourages further investigations on the identified isolates as starter cultures for fermented faba beans and faba bean-cereal products.

Wheat bran is obtained after conventional milling of wheat grains for the production of white flour, which is an important source of dietary fiber, vitamins and minerals, but still remains underutilized in food manufacturing. In spite of the increasing evidence about the health effects of whole-meal and fiber-rich foods, refined white flour is still preferred. Bran also has a negative influence on dough rheology, texture and the sensory quality of bread, which limits its use in bran bread baking. The use of starter culture for sourdough fermentation can drive the fermentation process and confer specific changes on the matrix. Exopolysaccharides (EPS) produced by some lactic acid bacteria (LAB) are important due to their physicochemical properties affecting dough rheology and bread texture, as well as their health-promoting potential. The screening of EPS-producing strains has been carried out mostly on wheat and rye sourdough, and very few studies have considered different matrices. The objective of this work was to determine and compare whole-wheat flour and wheat bran fermentation by two strains of LAB (Leuconostoc spp. and Weissella spp.) in the presence of added sucrose and without, and to study the effect of sourdough obtained with a selected EPS-producing LAB strain on the quality of bread and its shelf-life. Sourdough quality was studied by means of microbiological, rheological and chemical analysis by comparing the growth and acidification performance in the different matrices, and by evaluating EPS production using viscosity measurements. The physical and mechanical properties of fresh bread made using the best EPS producer LAB were investigated to study the product shelf-life by using the seed replacement method and texture analysis test. The results showed that dough prepared with Weissella confusa with added sucrose had a positive impact on viscosity, as well as providing mild acidic sourdough leading to better bread quality properties, whereas in the presence of Leuconostoc pseudomesenteroides, no positive viscosity has observed in whole-wheat sourdough. Bran sourdough samples with Weissella confusa showed a higher volume, better color and shelf-life during storage than samples with un-soured bran, confirming the effect of sourdough and the positive role of EPS on the functional properties of high-fiber bread making.

A review of the literature emphasised the significance of protein oxidation, which can lead to such modifications as the loss of essential amino acids and protein cross-links, and may bring about adverse effects on human nutrition and protein functionality. As the globulin fraction constitutes the predominant storage protein in oats, oxidation of oat globulin is in great need of attention and understanding. Oat globulin-containing oil-in-water emulsions were used as a food model. Thus, the objectives of the present work include the oxidation of oat proteins as well as lipid oxidation in prepared food emulsions together with a commercial oat protein-containing cream, and the possible antioxidant activities of berry phenolics (i.e. ellagitannins) towards protein oxidation. Oat globulin was extracted with a cold isolation buffer preceded by the removal of water-soluble impurities. Oxidation took place in darkness by placing the emulsion and cream samples in an oven with continuous stirring and a constant temperature at 37 oC. Sampling for lipid and protein oxidation measurements was carried out at day 0, 3 6 and 9. During the 9-day oxidation, no hexanal was detected in any oat protein-containing samples except for the ones without oat proteins, which were measured by headspace gas chromatography. The development of protein oxidation in prepared emulsions could not be revealed by the proposed loss of tryptophan fluorescence, as the tryptophan fluorescence actually increased and then decreased in the current study as opposed to continuous decrease as indicated in references, but carbonyl and dityrosine formation reflected the progression of protein oxidation. However, the same fluorescence techniques as in prepared emulsions ended up with contradictory fluorescence results in cream samples due to syneresis of oat creams during oxidation. In conclusion, fluorescence spectroscopy is a promising technique to investigate protein oxidation in food emulsions using carbonyl and dityrosine formation as oxidation markers.

The literature review related to faba bean proteins, the mechanism of protein oxidation and detection methods for protein oxidation as well as the relationship between lipid and protein oxidation. Native faba bean, faba bean treated by oven and microwave, as well as soy protein isolate were used as materials. The materials differed in their lipoxygenase activity. Oil-in-water emulsions were made of 10% purified (removal of antioxidants) rapeseed oil and 3% water soluble proteins that were extracted from flour samples. The emulsions were prepared by homogenizing using microfludizer. Oxidation took place in the oven at 37 °C in the dark with constant stirring by magnet stirrers. Sampling for measurements was carried out on day 0, 1, 4 and 7 from each replicate. Oxidative stability of was monitored by following lipid oxidation as formation of conjugated dienes and hexanal, and by following protein oxidation by measuring loss of tryptophan, formation of carbonyls and dityrosine through fluorescence detections both in the lipid phase and in the continuous phase. In this study, the degree of protein oxidation was generally consistent with corresponding lipid oxidation. Generally, the degree of protein oxidation in lipid phase of emulsions was higher than that in continuous phase, although the protein content was far less in the lipid phase. Both results implied co-oxidative relationship between lipid and protein oxidation. In addition, the results showed that thermal treatment or microwave irradiation can not only result in retarding or decreasing lipid oxidation by lowing lipoxygenase (LOX) activity, but also affect protein oxidation via lipid oxidation and the conformational changes of proteins.

Idli is a popular cereal-legume fermented food of Indian origin. It is steam cooked from fermented (lactic acid-yeast) batter of rice (cereal) and black gram (legume). Idli preparation process includes three major steps – soaking of rice and black gram, grounding and fermentation. The idli preparation process is laborious, as the whole procedure takes about 20 hours. Further, the fermented batter has a shelf life of 4-5 days at 4 ºC. Literature studies reveal less efforts has been taken to improve shelf life and nutritional quality of idli. The overall aim of this thesis was to improve the quality of idli batter by mild heat treatment (Objective 1) and through microbial applications (Objective 2-4). First, the fermented idli batter was mild heat (MH) treated (57, 60, 63, 66 and 70 ºC ) to reduce the high (10.5 log cfu/g) lactic acid bacteria and yeast counts for enhancing the shelf stability at refrigerated storage. MH treatment (at 70 ºC) induced the highest reduction (3.6 log cfu/g) without affecting the pasting profile of idli batter. During storage study (upto 10 days at 4 ºC) the microbial counts further decreased without change in pH.The second objective was to monitor the changes in physicochemical properties and B-vitamin (riboflavin, folate and vitamin B12) levels in idli batter fermentation on addition of starters - Lactococcus lactis N8 (SAA1) and Saccharomyces boulardii (YEA1). Fermentation profiles were recorded individually and in combination of starters. SAA1 and YEA1 were able to enhance or retain riboflavin and folate levels, but no change in vitamin B12 levels were observed during fermentation. Further, YEA1 individually and in combination with SAA1 significantly improved the idli batter volume, implying high gas production. The third objective was to produce nisin in idli batter by addition of SAA1 (nisin producer). The results highlighted SAA1 was capable of producing nisin in idli. However, the produced nisin was degraded by the activity of indigenous LAB and yeast in idli batter. The final objective of this thesis was to determine the viability of probiotic Bacillus coagulans (BAC1) spores after cooking (steaming and microwaving) and during storage (at 4 ºC) of idli batter. Microwave cooking resulted in higher reduction of BAC1 than steam cooking. However, 5.4 log cfu/g of BAC1 spores were still viable in steamed idli from the initial added amount (8.2 log cfu/g). The BAC1 spores were not stable in idli batter suggesting spore outgrowth during storage. In summary, these results present different strategies and information for future process and product developments in idli.

Toffee is a hard-textured confectionery product which is made by boiling together sugar, milk, and fat to a certain temperature. The aim of this study was to determine the suitability and effect of seven kinds of dairy powders in toffee processing. The recipes based on dry dairy powder content of 8.8% (1st series), and protein content of 3.5% with constant solid content compensated by sucrose (2nd series). Dairy powders used in this research were: skim milk powder (SMP); butter milk powder (BMP); whole milk powder (WMP); lactose-free skim milk powder (LF-SMP); lactose-free whole milk powder (LF-WMP); 40% demineralized whey powder (D40); and 70% demineralized whey powder (D70). Color, mechanical properties, water content, water activity (aw), and glass transition temperature (Tg) of final toffee samples were analyzed. Mechanical properties were examined after one week storage as well. The data obtained were analyzed by MATLAB and SPSS. In both series, toffees made of LF-SMP showed darkest color, and those containing WMP had lightest color. Higher water content and aw in the 2nd series resulted in softer and more sticky toffees than in the 1st series. Increasing content of protein and lactose increased the hardness of toffee in the 1st series. In the 2nd series, sucrose crystals produced gritty texture of toffee, leading to decreasing hardness and stiffness of toffee, but increasing stickiness. After one week storage, all the toffees became harder and more sticky. Toffees made from lactose free dairy powders always showed higher tendency to flow and deformation than the others, indicating the function of lactose in stability of toffee. In conclusion, increasing content of protein and lactose increased the hardness of toffee. Increasing content of protein and reducing sugar led to darker color of toffee. Higher water content and aw decreased hardness, stiffness, and stability of toffee, but increased stickiness. Increasing the content of sucrose decreased the hardness, stiffness, and stability of toffee as well. SMP showed highest suitability among seven kinds of dairy powders in toffee manufacture. BMP and WMP were also possible to be dairy source in the recipe of toffee. Lactose-free milk powder was not a good choice to form stable toffee.