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Rheological characteristics of alphaamylase treated cereal and pulse flour dispersions and doughs

Ambresh, P. (2010) Rheological characteristics of alphaamylase treated cereal and pulse flour dispersions and doughs. [Student Project Report]

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Abstract

This Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page.

Item Type: Student Project Report
Additional Information: Bengal gram flour dispersions and doughs have been treated with bacterial alpha-amylase at different concentrations of solids and time of enzyme treatment. The objective of the present work is to study the effect of these two variables on the rheological characteristics of the samples due to enzyme treatment. Rice flour doughs having solid concentrations of 47 and 50% are also subjected to compression textural testing. An increase in the concentration of solid markedly increases the maximum force, firmness and energy for compression for Bengal gram flour doughs. The dynamic oscillation rheological measurement generates data like storage modulus (G′), loss modulus (G″), loss angle (δ) and complex viscosity (η*) for flowable dispersions of Bengal gram. The concentration of solid in the dispersion and time of enzyme treatment affects the rheological indices of oscillation testing; an increase in both of these variables decreases G′, G″ and η* while no clear trend has been observed for δ. The flow behaviour index of the flowable dispersions varies from 0.405 to 0.666 indicating to be non-Newtonian shear thinning samples. The dispersion without enzyme treatment possesses the highest n value for the lowest concentrated dispersion sample and vice-versa. However, we have not observed any clear trend in n values with the time of enzyme treatment. It is possible that enzymatic degradation from starch produces lower molecular weight compounds that may be soluble or insoluble in water and their proportion may decide the n values. On the other hand, apparent viscosity and consistency index show a decreasing trend with an increase in time of enzyme treatment meaning that the consistency of the sample decreases markedly as the time of enzyme treatment is increased but they increase with an increase in concentration of solid. The untreated rice flour dough show significantly higher force compared to enzyme treated samples. The enzymatic degradation occurs markedly in the first phase of enzyme treatment (within 10 min). The uniaxial compression testing of dough exhibits an increase in force/energy/firmness values with an increase in solid concentration but decreases with time of enzyme treatment. However, these three indices show a similar trend. The electron photomicrographs of Bengal gram flour dispersions show spheroid and ellipsoid particles of dimensions between 8 and 25 μm; these particles are bonded by the leached out materials that happens during the process of dispersion preparation. The enzyme treated sample indicates the damage to the starch particles and broken/damaged fractions. Similar results are also observed with rice flour doughs but shows more damaged structures and cell fractions. The overall conclusions of the present investigation are that uniaxial compression and dynamic rheological testing of doughs and dispersions are suitable methods to monitor the changes that happen due to alpha-amylase treatment. The enzyme treated doughs are easier to flatten/roll compared to untreated samples. The possible applications of the generated data are for food industries that use cereals and pulses to develop products like spreads, flattened sheets, etc.
Uncontrolled Keywords: Bengal gram flour; Bengal gram flour doughs; rheological characteristics; enzyme treatment
Subjects: 600 Technology > 08 Food technology > 14 Physical properties > 03 Rheology
600 Technology > 08 Food technology > 21 Cereals
600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
600 Technology > 08 Food technology > 22 Legumes-Pulses
Divisions: Food Engineering
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 13 Jul 2010 09:29
Last Modified: 28 Dec 2011 10:16
URI: http://ir.cftri.com/id/eprint/9543

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