Dry fractionation of barley. A study o the glass transition temperatura of starch and protein
- Authors
- Torres Mart?nez, Jos? Alejandro
- Format
- MasterThesis
- Status
- publishedVersion
- Description
Barley is one of the most important cereals worldwide. About two-thirds of the barley production is used for feed, one-third for malting and 2% for human consumption. Low consumption as food and poor product development is related with its lower leaving capacity or colour development when comparing it wheat and rice respectively. However barley can be used as food ingredient in several products like unleavened products, cereals, pastries, etc. Barley is a low fat cereal containing several nutrients in which the most abundant are starch, protein and fibers like ?-glucan. A key strategy to increase the added value of barley is to produce enriched fractions of its components e.g. starch, protein. With this purpose, a better understanding of the breaking behaviour of the grain is needed. The breaking behaviour of the grain is determined by the mechanical properties of its components, which are influenced by the state they are in. In this research the glass transition temperature (Tg) of barley starch isolate (BSI) and barley protein isolate (BPI) were studied. The Tg is the temperature at which components change from a rubbery to a glassy state. In both states molecules form amorphous structures with different mechanical and thermal behaviour. A glass has a solid-like brittle behaviour and a rubber has a liquid-like behaviour with restricted capacity to deform or flow. Water is an important component of food products and has an enormous influence in the Tg of the components. In this research, the Tg of BSI and BPI were determined at several moisture contents and a state diagram was constructed using the Gordon-Taylor equation. Tg was measured with thermal mechanical compression test (TMCT). TMCT is a novel technique that measures the Tg by applying a constant force to a sample while increasing the temperature. When the samples changes from glassy to rubbery, there is a change in volume that is measured and Tg can be determined. The outcome of this research was compared with measurements of the Tg for the isolates obtained with differential scanning calorimetry (DSC) in a previous study. DSC is a widely used technique that measures the Tg by detecting changes in heat capacity. The drawback of DSC is that changes in heat capacity are very small and the interpretation of the data might be ambiguous. To have a clearer interpretation and to avoid side effects, during DSC samples are heated, cooled and heated again. The Tg is measured during the second heating but denaturation and/or degradation of the components during the first heating might be an important complicating factor...
- Publication Year
- 2014
- Language
- eng
- Topic
- TERMODIN?MICA
ESCANEO CALORIM?TRICO
CEBADA
FRACCIONAMIENTO EN SECO
- Repository
- Repositorio SENESCYT
- Rights
- openAccess
- License
- openAccess