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Effect of amino acid, pH and mineral salts on glass transition and flow behaviour of soy protein concentrate
Author(s) -
Ahmad Rafiq,
Samuelsen Tor Andreas,
Garvik Anne B.,
Oterhals Åge
Publication year - 2018
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/ijfs.13720
Subject(s) - proline , chemistry , moisture , soy protein , food science , glass transition , factorial experiment , plasticizer , central composite design , amino acid , extrusion , response surface methodology , chromatography , biochemistry , materials science , organic chemistry , mathematics , statistics , metallurgy , polymer
Summary The objective of this study was to assess the effect of proline, mineral salts (NaCl and Na 2 SO 4 ) and pH combined with moisture content on the glass transition temperature ( T g ) and flow‐starting temperature ( T f ) of soy protein concentrate ( SPC ). Initial screening of the variables based on fractional factorial design showed insignificant effect of NaCl on T g and T f . The design was extended to a face‐centred central composite design ( CCD ) excluding NaCl and data evaluated by use of response surface methodology. The established model for T g ( R 2 = 0.824) shows significant negative first‐order effects of moisture, proline and Na 2 SO 4 , and a positive interaction effect of moisture and Na 2 SO 4 . The T f model ( R 2 = 0.937) shows significant negative first‐order effects of moisture and proline, a positive first‐order and negative square effect of pH , and a negative interaction effect of moisture and proline. The main effect on T g and T f was 2.2 and 1.3 times higher, respectively, for moisture compared to proline. The study confirms that proline (or other free amino acids) can replace moisture as protein plasticiser in the extrusion process. Minor effects can also be obtained by reduction in pH .