40 research outputs found
Effect of puroindolines on dough rheological properties
No full textPuroindolines proteins are related to grain hardness and affect milling yield, flour particle size, damaged starch content and water absorption. Little information is available on the role of puroindolines in dough rheology. This study aimed at investigating the rheological properties of durum wheat (T. durum, Svevo cv, S), soft-textured durum wheat (Soft Svevo, SS), soft wheat (T. aestivum, Alpowa cv, A) and hard-textured wheat (Alpowa with 5DS distal end deletion, AD). Samples were kindly provided by Dr Morris (USDA-ARS, Western Wheat Quality Lab). Gluten aggregation properties (GlutoPeak test, GPT), dough mixing properties (Farinograph test), extensibility (micro-Extensograph test), and pasting properties (Micro-Visco-Amylograph test, MVAG) were measured. GPT profiles showed AD exhibited a higher area under the curve than A (1498 vs 787 GPE) at maximum torque, indicating strong gluten. SS showed a lower area under the curve than S (969 vs 1467 GPE) at maximum torque. Differences in particle size and damaged starch (S vs SS and A vs AD) are responsible for differences in maximum torque (GPT), water absorption and dough development time. Moreover, AD showed higher stability than A (8.5 vs 2.2 min). While, dough from SS was slightly less stable than dough from S (3.3 vs 2.5 min). AD showed higher resistance to extension than A (108 vs 82 BU), while no differences in dough extensibility were measured between S and SS. MVAG profiles showed that AD had lower pasting temperature (59 vs 61 ∘C), higher peak viscosity (638 vs 566 BU), lower breakdown (303 vs 323 BU) and higher setback values (746 vs 631 BU) than A. Conversely, SS showed higher pasting temperature (60.8 vs 58.3 ∘C) and higher peak viscosity (723 vs 849 BU) than S. This study showed that puroindolines affect rheological properties and pasting properties, but the trend is different in T. aestivum and T. durum
Empirical rheology and pasting properties of soft-textured durum wheat (Triticum turgidum ssp. durum) and hard-textured common wheat (T. aestivum)
No full textPuroindoline (PIN) proteins are the molecular basis for wheat kernel texture classification and affect flour milling performance. This study investigated the effect of PINs on empirical rheology and pasting properties in Triticum turgidum ssp. durum and Triticum aestivum. Soft wheat (cv. Alpowa), durum wheat (cv. Svevo) and their derivatives in which PINs were deleted (Hard Alpowa) or expressed (cv. Soft Svevo). Presence of PINs affected flour particle size and damaged starch. PINs increased the pasting temperature and breakdown viscosity, while the effect on peak viscosity and setback were not consistent. Presence of PINs was negatively associated with GlutoPeak gluten aggregation energy and farinograph dough stability, suggesting a weakening of the gluten matrix. As regards dough extensibility, the role of PINs was evident only in common wheat: 5DS distal end deletion increased the resistance to extension, without affecting the dough extensibility. This study showed PINs to have different impact on pasting and rheological properties of T. aestivum and T. turgidum ssp. durum flours
Effect of mixing temperature on protein secondary structure and thiols in soft and hard wheat flour dough
No full textDough rheology is important to manufacture different food products. This has primarily been attributed to the differences in flour protein content. Temperature has significant influence on gluten properties and dough rheology. The objective of this study was to find out conformational changes and differences in thiol content of dough from soft wheat flour (SWF) and hard wheat flour (HWF) mixed at four temperatures (4, 15, 30, 40°C). Doughs were sampled at four points - dough development time (DDT), mid-stability (MS), stability departure (SD) and time to breakdown (TBD). Conformational changes of sampled doughs were studied using attenuated total reflectance Fourier transform infrared (ATR/FTIR) spectroscopy and thiols by DNTB assay. There were significant increases in beta sheets and decreases in beta turns for SWF at DDT and SD as mixing temperature increased. Changes in beta sheets and beta turns in HWF at DDT and SD as mixing temperature increased were not significant. The 30°C HWF dough showed significant decrease in accessible thiols with a corresponding increase in total thiols during mixing for all the sampling points. In SWF dough, there were increases in accessible and total thiols during mixing for the 30°C sample. HWF exhibited more accessible thiols though the two had comparable total thiols. Susceptibility of beta sheets and turns to changes in SWF and the low accessible thiols may explain why soft wheat has short dough development time and short stability
Effect of puroindolines on protein characteristics in flour and dough
No full textPuroindolines are wheat endosperm proteins that account for most differences in kernel texture among soft, hard, and durum wheat. Puroindolines expression results in soft kernel texture, whereas mutations in one or both genes controlling their expression results in a hard texture. This study aimed at investigating the effect of puroindolines on some features of wheat proteins in both flour and dough.
Flours and related doughs were characterized for 1% SDS protein solubility, 1% SDS-accessible thiols content, surface hydrophobicity, and conformation, using durum wheat (Svevo cv, S), soft-textured durum wheat (Soft Svevo, SS), soft wheat (Alpowa cv, A) and hard-textured wheat (Alpowa with 5DS distal end deletion, AD). Puroindolines expression resulted in a significant (p<0.05) decrease in soluble proteins (S: 867; SS: 504 mg/g protein) and in SDS-accessible thiols (S: 12.4; SS: 8.2 micromol/g protein) in flours. On the other hand, 5DS distal end deletion resulted in a significant (p<0.05) increase in the amount of soluble protein (A: 537; AD: 816 mg/g protein) and of SDS-accessible thiols (A: 5.6; AD: 7.0 micromol/g protein) in flours.
No significant (p<0.05) differences related to puroindolines expression were found in either protein solubility or thiol content in dough, if not for 5DS distal end deletion affecting the thiols content (A: 5.9; AD: 7.2 micromol/g protein). Puroindolines expression (S vs SS) resulted in a decrease in protein surface hydrophobicity, whereas the 5DS distal end deletion (AD vs A) did not change protein hydrophobicity. Both expression and deletion caused an increase in beta-turn structures (S: 40.1%; SS: 46.8%; A: 35.4%; AD: 40.3%). In conclusion, puroindolines seem to affect some gluten proteins overall characteristics, but specific effects seem to be species-dependent
Structural modification of gluten proteins in strong and weak wheat dough as affected by mixing temperature
No full textThe effects of temperature (≥25°C) on dough rheological properties and gluten functionality have been investigated for decades, but no study has addressed the effect of low temperature (<30°C) on gluten network attributes in flours with strong and weak dough characteristics. This study monitored changes in protein extractability in the presence and absence of reducing agents, the contents of readily accessible and SDS-accessible thiols, and the secondary structural features of proteins in doughs from commercial hard wheat flour (HWF) and soft wheat flour (SWF) mixed at 4, 15, and 30°C. SWF mixed at 4 and 15°C showed similar mixing properties as HWF mixed at 30°C (which is the standard temperature). The effect of mixing temperature is different at the molecular level between the two flours studied. Protein features of HWF did not change as mixing temperature decreased, with the only exception being an increase in SDS-accessible thiols. Decreasing mixing temperature for SWF caused an increase in SDS protein solubility and SDS-accessible thiols as well as an increase in β-turn structures at the expense of β-sheet structures. Thus, noncovalent interactions appear to drive protein network at low temperatures (4 and 15°C), whereas covalent interactions dominate at standard mixing temperature (30°C) in doughs from both flours
Structural consequences of the interaction of puroindolines with gluten proteins
No full textThe effect of puroindolines (PINs) on structural characteristics of wheat proteins was investigated in Triticum turgidum ssp. durum (cv. Svevo) and Triticum aestivum (cv. Alpowa) and in their respective derivatives in which PIN genes were expressed (Soft Svevo) or the distal end of the short arm of chromosome 5D was deleted and PINs were not expressed (Hard Alpowa). The presence of PINs decreased the amount of cold-SDS extractable proteins and the accessibility of protein thiols to specific reagents, but resulted in facilitated solvation of gluten proteins, as detected by tryptophan fluorescence measurements carried out on minimally mixed flour/water mixtures. We propose that PINs and gluten proteins are interacting in the grain or flour prior to mixing. Hydrophobic interactions between PINs and some of the gluten proteins modify the pattern of interactions among gluten proteins, thus providing an additional mechanistic rationale for the effects of PINs on kernel hardness
Shadow Education:Its nature role and function in British International schools in Hong Kong.
No full textShadow education is the term frequently used to describe the provision of supplementary education by tutoring agencies, ‘cram schools’ and other private, typically for-profit organisations that assist in the achievement of successful examination results. This thesis will attempt to research the role which ‘shadow education’ plays in modern day Hong Kong. A study undertaken in 1998 revealed that on average 41 per cent of grade 3 students and 39 per cent of grade 6 students were participating in shadow education. This seems to be part of a wider international trend in both developed and developing countries, including the UK. With a system comparable to the British education system, Hong Kong has experienced growth in its shadow education system as well. While a number of studies have examined the economic and policy implications of shadow education, few have undertaken thorough research of the sociological factors that might contribute to its popularity. This study aims to investigate the historical, socio-economic factors that influence the choice of shadow education in Hong Kong. In this way, it followed the precedent set by British researchers Ireson and Rushforth, who conducted a similar study of private tutoring in the UK. In order to understand the policy and social implications of shadow education, the system needs to be placed into a wider socio-political historical, economic and cultural context to reflexively frame both its existence and its acceptance amongst parents, students, education providers, and education policy-makers in Hong Kong. This study has hopefully provided both the context and the impact of shadow education in this particular example, but with wider application once the historical and sociological contexts are understood. This discussion and analysis placing the study’s primary data results from questionnaires, interviews, and focus groups hopefully demonstrates that the historical and social context of Hong Kong plays at least, if not more, of a role in the choice to participate in shadow education as pure economic practicality and functionalism. Shadow education fills a role in education that is social and confidence building, and also ameliorates some of the postcolonial anxieties of parents who grew up in a very different context than they find their children. While social mobility and economic gain clearly play a role in all of these considerations, the role of the shadow education system extends beyond the functionalism it is currently assigned in the literature
The Importance of Place in the Definition of Aboriginality in Aboriginal Women’s Fiction
No full textOvarian Cancer in Ghana, a 10 Year Histopathological Review of Cases at Korle Bu Teaching Hospital
No full textTo determine the histopathological types, age distribution, presenting signs and symptoms of ovarian cancers diagnosed at the Korle-Bu Teaching Hospital, Ghana. All histopathology slides and request cards of ovarian cancers diagnosed over a ten-year period (2001 to 2010) were reviewed and the cancers classified according to the World Health Organization 1999 classification. Biographical and clinical data of the patients were collected and results entered into Epi-info to determine the frequency, age distribution and clinical presentation of the various types of ovarian cancer. There were 192(27.2%) ovarian cancers out of 706 ovarian tumours. Epithelial cancers were the most common: 100 (52.1%), followed by sex cord stromal cancers 66 (34.4%). Majority of epithelial cancers were serous adenocarcinomas (71/100) while most sex cord stromal cancers were adult granulosa cell tumours 46 (69.7%). The mean age of patients with adenocarcinoma was 49 years while that of the 46 adult granulosa cell tumours was 46.5years. Patients present with varying combinations of symptoms and signs and ovarian cancers present at an earlier age compared to other populations, with the age of presentation being slightly lower for sex cord stromal cancers compared to adenocarcinomas. There are no specific symptoms or signs associated with ovarian cancer at presentation, to assist with diagnosis.Keywords: Ovary, Cancer, Histopathology, Demographics, Clinical features, Ghan
