Change search
ReferencesLink to record
Permanent link

Direct link
The effect of pH on hydrolysis, cross-linking and barrier properties of starch barriers containing citric acid
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
Department of Food Science, Swedish University of Agricultural Sciences .
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.ORCID iD: 0000-0001-7368-7227
Department of Food Science, Swedish University of Agricultural Sciences.
Show others and affiliations
2013 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 98, no 2, 1505-1513 p.Article in journal (Refereed) Published
Abstract [en]

Green cross-linking of thermoplastic starch for food packaging applications has been intensely studied during the last decade as a method of producing water-insensitive renewable barriers. This work has shown how the barrier properties of paper coated with a barrier dispersion containing starch and citric acid were affected by the solution pH and the drying temperature. The barrier properties of the coated paper were linked to molecular properties showing both hydrolysis and cross-linking reaction of starch in the presence of citric acid at different solution pH and different reaction temperatures (curing) on cast films. Hydrolysis was shown to be almost completely hindered at solution pH ≥4 at curing temperatures ≤ 105 °C and at pH ≥ 5 at curing temperatures ≤150 °C, whereas cross-linking still occurred to some extent at pH ≤ 6.5 and drying temperatures as low as 70 °C. The water vapor transmission rate was significantly affected by the competition between these two reactions. Coated paper showed a minimum in water vapor transmission rate at pH was kept around 4 in the starch coating solution, corresponding to the point where hydrolysis was effectively hindered but where a significant degree of cross-linking still occurred.

Place, publisher, year, edition, pages
2013. Vol. 98, no 2, 1505-1513 p.
Keyword [en]
starch; cross-linking; hydrolysis; molecular structure; barrier properties; citric acid
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kau:diva-27081DOI: 10.1016/j.carbpol.2013.07.040ISI: 000326313600034PubMedID: 24053833OAI: oai:DiVA.org:kau-27081DiVA: diva2:618316
Projects
Renewable Functional Barriers
Funder
VINNOVA
Available from: 2013-04-26 Created: 2013-04-26 Last updated: 2016-01-26Bibliographically approved
In thesis
1. Effects of Citric Acid on Starch-Based Barrier Coatings
Open this publication in new window or tab >>Effects of Citric Acid on Starch-Based Barrier Coatings
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With growing environmental concerns, efforts are made to replace petroleum based products with renewable alternatives. This is particularly evident in the packaging industry, where replacing synthetic polymers with renewable materials is of considerable interest. Materials for food packaging need to give protection, acting as a barrier against substances that can adversely affect the food quality such as water and oxygen.

In this work, barrier dispersion coatings based on starch were used to produce coated papers which act as barrier against water and oxygen. However, since starch is both a hydrophilic and hygroscopic material, this barrier material becomes problematic to use at high relative humidity. In order to reduce this problem and improve the barrier properties enabling starch based barrier materials to be used in food packaging applications, two approaches were studied.

Citric acid was utilized as a cross-linker of the starch and it was found to reduce the moisture sorption, the molecular movement and swelling at high relative humidity. It was seen that cross-linking and hydrolysis due to the low pH both affected the barrier properties significantly, but in opposing directions. By controlling these two reactions it was seen that this could lead to reduced gas permeability. It was also seen that cross-linking of starch by citric acid occurs at low temperatures, 70 °C at pH as high as 6.5.

Starch nano-composites were produced by incorporating montmorillonite, to the barrier dispersion to improve the barrier properties. It was seen that the suspension viscosity was reduced by poly(ethylene glycol) and citric acid adsorption on the montmorillonite particles. Also, a tendency for improved barrier properties with reduced aggregate volume fraction and reduced swelling was observed. It was also seen that up scaling this formulation to pilot scale was possible and that promising results were achieved.

Abstract [en]

Baksidestext

With growing environmental concerns, efforts are made to replace petroleum based materials with renewable alternatives such as starch. In this work, dispersions based on starch were used to produce coated papers which act as barrier against substances that can adversely affect the food quality such as water and oxygen. However, since starch is both a hydrophilic and hygroscopic material, this barrier material becomes problematic to use at high relative humidity.

Citric acid was utilized as cross-linker for starch and it was found to reduce the moisture sorption, diffusion and swelling at high relative humidity. Both cross-linking and hydrolysis due to the low pH affected the barrier properties significantly, but in opposing directions. By controlling these two reactions it was possible to achieve reduced gas permeability.

Starch nano-composites were produced by incorporating montmorillonite clay, to the barrier dispersion. It was seen that the suspension viscosity was reduced by poly(ethylene glycol) and citric acid adsorption on the clay. Also, a tendency for improved barrier properties with reduced aggregate volume fraction and reduced swelling was observed. It was also seen that up scaling this formulation to pilot scale was possible and promising results were achieved.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2013. 80 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2013:25
Keyword
Starch, Citric acid, Cross-linking, hydrolysis, Montmorillonite, WVTR, OTR, Barrier properties
National Category
Polymer Technologies
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-27127 (URN)978-91-7063-502-1 (ISBN)
Public defence
2013-06-13, 9C203, Nyquistsalen, Karlstads universitet, 10:15 (English)
Opponent
Supervisors
Projects
Renewable Functional Barriers
Funder
Vinnova
Available from: 2013-05-23 Created: 2013-04-29 Last updated: 2013-05-23Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Olsson, ErikJohansson, CaisaJärnström, Lars
By organisation
Department of Engineering and Chemical SciencesDepartment of Chemical Engineering
In the same journal
Carbohydrate Polymers
Polymer Technologies

Search outside of DiVA

GoogleGoogle Scholar

Altmetric score

Total: 179 hits
ReferencesLink to record
Permanent link

Direct link