• Login
    View Item 
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • College of Fisheries and Ocean Sciences
    • View Item
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • College of Fisheries and Ocean Sciences
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Scholarworks@UACommunitiesPublication DateAuthorsTitlesSubjectsTypeThis CollectionPublication DateAuthorsTitlesSubjectsType

    My Account

    Login

    First Time Submitters, Register Here

    Register

    Statistics

    Display statistics

    Screw configuration effects during twin-screw extrusion of starchy and proteinaceous materials

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Gautam_A_1998.pdf
    Size:
    4.149Mb
    Format:
    PDF
    Download
    Author
    Gautam, Akhilesh
    Chair
    Choudhury, Gour S.
    Committee
    Hansen, Conly S.
    Das, Debendra K
    Kramer, Donald E.
    Kelley, John K.
    Smiley, Scott T.
    Keyword
    Food science
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/9477
    Abstract
    This study investigated the effects of screw configuration and feed composition during extrusion of starchy and proteinaceous materials. All experiments were carried out in a twin-screw extruder with a length/diameter ratio of 32:1. The screw speed, feed flow rate, and moisture content were 400 rpm, 12 kg/h, and 15%, respectively. Kneading block (KB) and reverse screw elements (RSE) were placed at different locations in the 200 mm experimental zone near the die, where the temperature was maintained at $\rm 150\sp\circ C.$ An on-line method for measurement of residence time distribution (RTD) in a food extruder was developed, tested, and validated. The technique was based on the electrical conductivity of the material in the die, which was altered by addition of an electrolyte tracer at the feed inlet. The change in current flow was measured as a proportional voltage response across a resistor. The on-line method correlated well with the established erythrosine dye method and precisely determined the effects of screw speed, feed flow rate, screw configuration on RTD. The effects of type, length and position of mixing elements and spacing between two elements on energy inputs, RTD, molecular changes of starch, and macroscopic extrudate characteristics were compared. The results showed that the specific mechanical energy (SME), mean residence time, and extent of starch breakdown were higher for screw profiles with RSE than that with KB. These parameters also increased with longer mixing elements, increased distance of the elements from the die, and with increased spacing between two elements. Specific thermal energy (STE) input showed opposite trend to that of SME. Die temperature was highest when the elements were placed at 0 mm from the die. Such a screw profile produced an extrudate with highest overall expansion and lowest apparent density. Radial expansion was highest with KB in the screw profile than with RSE. KB seemed to be the element of choice for maximizing radial expansion. Increasing mixing element length or spacing between two elements decreased product expansion. Hardness of the product decreased linearly with increasing radial expansion as shown by the breaking strength data. Changing feed composition by adding Arrowtooth flounder muscle decreased the SME input, increased STE and mean residence time. Hydrolysis changed the properties of Arrowtooth flounder muscle so much that it enhanced the expansion characteristics of starch in rice flour and improved extrudate texture.
    Description
    Dissertation (Ph.D.) University of Alaska Fairbanks, 1998
    Date
    1998
    Type
    Dissertation
    Collections
    College of Fisheries and Ocean Sciences
    Theses (Unassigned)

    entitlement

     
    ABOUT US|HELP|BROWSE|ADVANCED SEARCH

    The University of Alaska Fairbanks is an affirmative action/equal opportunity employer and educational institution and is a part of the University of Alaska system.

    ©UAF 2013 - 2023 | Questions? ua-scholarworks@alaska.edu | Last modified: September 25, 2019

    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.