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Carrageenans are sulphated polysaccharides obtained from red seaweeds. They play an important role due to their gelling, thickening and stabilizing properties, which are widely used in the food, cosmetics and pharmaceutical industries. In the commercial process of carrageenans, heat is generally employed during extraction and drying that can affect the polysaccharides' functional properties. Therefore, the aim of this study was to investigate the thermal treatment (75-115 °C for 15 minutes) on the rheological behaviour of k-, k/l-, i-carrageenan and furcellaran gels. All studied polysaccharides showed a storage modulus (G') vs. frequency dependence and can be categorized as a typical physically cross-linked network gel. No changes in gel strength values were observed with 2.5% (w/v) k-, k/l-, i- carrageenan gels during thermal treatment. However, 2.5% (w/v) furcellaran formed thermally unstable gels as the gel strength was decreasing with increasing the treatment temperature. The melting and gelling temperatures were decreasing with increasing the heat treatment temperature for all carrageenans while furcellaran was most affected by thermal treatment. [ABSTRACT FROM AUTHOR]

Ice-binding proteins (IBPs) are polypeptides produced by organisms living in cold environments to prevent ice crystal growth or recrystallization. Several food-spoiling microbes can grow at refrigerator temperatures (2-6 oC), therefore temperatures close to or below zero are preferred for long-time storage. However, decreasing the temperature to the melting point is challenging as it might cause freezing damage due to time-spatial temperature fluctuations. A solution to the problems related to ice formation in chilled and frozen products might be the addition of IBPs. Our collaboration partner has recently screened 60 psychrophilic bacterial cultures, isolated and found a strain (Pseudomonas fluorescens) capable of secreting IBPs. The main goal is to investigate the potential of using Pseudomonas fluorescens IBPs to improve frozen foods' quality and storage time. For that purpose, the growth and excretion of IBPs by the respective strain of Pseudomonas are characterized, the protein is isolated, its DNA and protein sequence are established, and the mechanisms of action in food storage conditions are evaluated. Preliminary experiments have shown that the protein is stable at various temperatures and in the neutral pH range. The strain requires organic nitrogen to produce IBPs and the addition of L-asparagine or L-proline to the culture broth appears to have a positive effect on the production of IBPs. The incorporation of Pseudomonas fluorescens culture broth containing IBPs improved the quality of frozen wheat dough stored at -20 oC for eight weeks. It exhibited higher yeast survival rates and better yeast vitality. Additionally, the bread prepared from the frozen dough had better specific volume, porosity, and softness. Although additional experiments should be conducted, this shows that the protein has the potential to be used to improve the quality of frozen dough products. [ABSTRACT FROM AUTHOR]