Browsing by Subject "gluten-free"

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  • Luoto, Sanna (Helsingfors universitet, 2011)
    The literature review dealt with celiac-toxic Triticeae prolamins and their enzymatic degradation. Also the immunochemical methods for prolamin analysis were introduced. The gluten-derived immunogenic peptides are proline-rich and thereby remarkably resistant to proteolytic degradation. Most of the triggering prolamins can, however, be degraded by combining endogenous cereal enzyme activity with acidic incubation. Despite of this residual prolamins still exist and their concentration exceeds the threshold considered to be safe for gluten intolerants. The objective of the experimental work was to further hydrolyse the residual prolamins present in malt autolysates of wheat, barley and rye, with a food grade proline endopeptidase from Aspergillus niger (AN-PEP). Size-exclusion chromatography (SEC), free amino nitrogen (FAN) and SDS-PAGE analysis determined the extent of protein hydrolysis. Actual prolamin degradation was observed with immunological methods. Hydrolysis of residual prolamins was extensive in all malt systems – more than 96% of the prolamins were hydrolysed. The SEC and FAN data revealed that continuation of the hydrolysis overnight converted the polypeptides into smaller hydrolysis products. According to enzyme-linked immunosorbent assay analyses, 22 h incubation decreased the prolamin contents of wheat and rye malt hydrolysates below the level of 100 mg/kg. This level was achieved with AN-PEP concentration of 35 ?L/g in relation to freeze-dried autolysate. According to the Codex Alimentarius, food products containing gluten up to 100 mg/kg can be labelled 'very low gluten' and thus included in coeliac diet. AN-PEP treated rye malt ingredient could especially be a promising low-gluten ingredient to enhance the flavour of often poor-quality gluten-free bread. Before commercial applications can be devised the potential as a flavouring agent as well as the clinical safety of the product must be evaluated.
  • Huang, Xin; Ma, Kaiyue; Leinonen, Sara; Sontag-Strohm, Tuula (2020)
    The lack of certified reference materials has been one major challenge for gluten quantification in gluten-free products. In this study, the feasibility of using barley C-hordein as the calibrant for wheat gluten in R5 sandwich enzyme-linked immunosorbent assay (ELISA) was investigated. The gluten composition and total gluten R5 reactivity ranged largely depending on the genotypes and the growing environment. The conversion factor of gliadin to gluten averaged 1.31 for common wheat, which is smaller than the theoretical factor of 2. Each gluten group had varying reactivity against the R5 antibody, where omega 1.2-, gamma- and alpha-gliadins were the main reactive groups from wheat gluten. A mixture of wheat cultivars or one single cultivar as the reference material can be difficult to keep current. Based on the average R5 reactivity of total gluten from the 27 common wheat cultivars, here we proposed 10% C-hordein mixed with an inert protein as the calibrant for wheat gluten quantification. In spiking tests of gluten-free oat flour and biscuits, calibration using 10% C-hordein achieved the same recovery as the gliadin standard with its cultivar-specific conversion factor. For its good solubility and good affinity to the R5 antibody, the application of C-hordein increases the probability of developing a series of reference materials for various food matrices.
  • Rekola, Kristiina (Helsingfors universitet, 2015)
    Chemical composition of oats and its suitability for baking were reviewed in the literature part. The special features of baking without gluten and possibilities to increase the quality of gluten-free bread were also discussed. The aim of the experimental research was to develop high protein gluten-free oat-based bread. The effect of different protein concentration on structural, textural and sensory properties of gluten-free oat bread was studied. Also the effect of processing method on bread quality was studied by using sourdough technology and straight dough technology. Gluten-free oat bread recipe and baking protocol as well as sourdough fermentation conditions were optimized on the basis of preliminary trials. Oat-based breads with varying protein content were baked by using straight dough and sourdough technologies. Reference sample was oat-based bread without added protein. Specific volume, moisture content, texture profile analysis (crumb hardness, chewiness and resilience) and starch retrogradation of gluten-free breads were analysed. For shelf life measurements, breads were stored in plastic bags at room temperature from 1 to 3 days. Sensory profile of bread samples were evaluated on the day of baking by a trained panel. Descriptive analysis method was used. Palatable high protein gluten-free oat-based bread was obtained in this study. Increasing amount of protein improved the crumb structure and shelf life of gluten-free breads. All of the protein supplemented breads had agreeable sensory profile. Sourdough did not further improve the quality of high protein gluten-free bread except for increased aroma intensity. Oats and its fractions can be successfully applied as an ingredient for gluten-free baking to enhance the nutritional quality.
  • Ahola, Hanna Gabriela; Sontag-Strohm, Tuula; Schulman, Alan; Tanhuanpää, Pirjo; Viitala, Sirja; Huang, Xin (2020)
    Oats have been found to be tolerated by most celiac disease patients, and oats are generally considered a good and safe addition to the gluten-free diet. There have been claims that some individual oat cultivars are harmful or immunogenic for celiac disease patients. In this study, we investigated 26 oat cultivars and landraces from the current breeding market and literature. Their total protein content ranged from 15.3% to 23.1% of which avenins ranged from 6.8% to 10.9%. Immunological activities of avenins were evaluated using mmunochemical analyses using monoclonal antibodies (mAb) R5 and G12. No immunological activity of the oat cultivars was observed by mAb R5 either in immunoblotting or enzyme-linked immunosorbent assay (ELISA). mAB G12 showed no activity in immunoblotting, but gave responses between 13 and 53 mg/kg in ELISA for total avenin extract. To understand the varying G12 activity, avenins were further fractionated. One avenin fraction showed a higher G12 response than the other fractions. Protein sequence comparison suggests that there is no direct binding to avenin-specific T-cell epitopes but the differences in repetitive regions in avenins may contribute to varying results in G12 ELISA.
  • Aalto, Kaisa (Helsingin yliopisto, 2019)
    Kauran käyttö leivonnassa on kasvattanut suosiotaan viime vuosien aikana. Gluteenittomuuden takia 100 % kauraleivonta on kuitenkin haasteellista, sillä taikinan käsiteltävyys vaikeutuu sitkon puuttuessa. Oikeanlaisen taikinan konsistenssin saavuttamiseksi ja onnistuneen leivonnan kannalta on tärkeää tunnistaa kauran vedensidontakykyyn vaikuttavat tekijät. Tutkimuksessa tarkasteltiin eri kauralajikkeiden beetaglukaanipitoisuuden yhteyttä vedensidontaan. Tavoitteena oli myös vertailla eri kauralajikkeista tehtyjen taikinoiden konsistenssia ja valmiiden leipien rakenteellisia ja aistinvaraisia ominaisuuksia. Kokeellisessa osiossa tutkittiin viidestä eri kauralajikkeesta valmistettujen jauhojen ja hiutaleiden vedensidontaa ja siihen vaikuttavia tekijöitä. Taikinan konsistenssimittauksia ja leivontakokeita varten näytteistä valmistettiin kaksi erilaista taikinaa, joissa toisessa käytettiin pelkästään kaurajauhoja ja toisessa puolet kaurajauhoista korvattiin saman lajikkeen kaurahiutaleilla. Leivonnan onnistumiseksi taikinoissa käytettiin apuna psylliumia. Kaurajauhoista sekä kaurajauhoista ja -hiutaleista valmistettujen taikinoiden konsistenssia tutkittiin aineenkoestuslaitteella (Texture Analyzer) käänteisen ekstruusion avulla. Leivontakokeissa leivottiin palaleipiä, joiden rakenteellisten ominaisuuksien muutoksia seurattiin myös aineenkoestuslaitteen avulla (Texture Profile Analysis). Tulosten perusteella lajikkeen vaikutus kauran vedensidontakykyyn, konsistenssiin ja leivontatuloksiin oli suuri. Beetaglukaanipitoisuuden yhteys kaurajauhojen vedensidontakykyyn ei ollut selkeä, mutta kaurahiutaleiden vedensidonta suureni beetaglukaanipitoisuuden suuretessa. Kauralajikenäytteiden konsistenssi riippui monesta eri tekijästä. Suuri beetaglukaani- ja proteiinipitoisuus näkyi suurena taikinoiden konsistenssina. Kaurahiutaleita sisältävien taikinoiden konsistenssi oli suurempi kuin vain kaurajauhoja sisältävien taikinoiden. Suuri taikinan konsistenssi helpotti taikinan käsittelyä ja muokkaamista. Konsistenssin suuruudella ei ollut suoraa yhteyttä valmiiden leipien rakenteellisiin ominaisuuksiin. Muutokset leipien rakenteessa tapahtuivat kypsymisen aikana ja johtuivat todennäköisesti lajikkeiden erilaisista liisteröitymislämpötiloista ja tärkkelyksen käyttäytymisestä paiston aikana. Liisteröityneen kauran lisääminen taikinan joukkoon paransi leipien rakenteellisia ominaisuuksia ja säilymistä.
  • Huang, Xin; Kanerva, Paivi; Salovaara, Hannu; Stoddard, Frederick L.; Sontag-Strohm, Tuula (2017)
    The concentration of residual barley prolamin (hordein) in gluten-free products is overestimated by the R5 ELISA method when calibrated against the wheat gliadin standard. The reason for this may be that the composition of the gliadin standard is different from the composition of hordeins. This study showed that the recognition of whole hordein by R5 antibody mainly came from C-hordein, which is more reactive than the other hordeins. The proportion of C-hordein in total hordein ranged from 16 to 33% of common Finnish barley cultivars used in this study and was always higher than that of omega-gliadin, the homologous protein class in the gliadin standard, which may account for the overestimation. Thus, a hordein standard is needed for barley prolamin quantification instead of the gliadin standard. When gluten-free oat flour was spiked with barley flour, the prolamin concentration was overestimated 1.8-2.5 times with the gliadin standard, whereas estimates in the correct range were obtained when the standard was 40% C-hordein mixed with an inert protein. A preparative-scale method was developed to isolate and purify C-hordein, and C-hordein is proposed as a reference material to calibrate barley prolamin quantification in R5-based assays.