**5. Acknowledgment**

This work was supported by grants from the Universidad Nacional de Rosario. Thanks to MSc. Luis Martínez of the National University of Quilmes for their advice in the rheological measurements. Thanks to Prof. Mirta Armendariz of the National University of Rosario for their advice in the statistical analysis. The authors would like to thank Lic. Romina Ingrassia for the English revision.

### **6. References**

86 Food Industrial Processes – Methods and Equipment

Performing a qualitative analysis of these images, it is possible to observe different degrees of structure of the gels formed at different ratios of CMC. Table 3 shows the values of mean pore size of NaCAS gels in the absence and presence of CMC obtained from digital images. In the presence of lower concentration of CMC, the slower rate of gelation (higher tg) produced gels more structured, more compact and with smaller pores. This is due to, if the process is performed slowly, the gel mesh can be restructured by breaking of some interactions and formation of new ones, forming a tighter mesh and, therefore, progressively smaller pores. Other authors have also reported that processing speed can affect the hardness and elasticity of the gel formed (Cavallieri & da Cunha, 2008). But with increasing CMC concentration, there was an increase in the average pore diameter. Mixtures

System Average pore sizes (m)

NaCAS 3% 3.1 ± 0.4 NaCAS 3%-CMC 0.375% (8:1) 2.7 ± 0.2 NaCAS 3%-CMC 0.50% (6:1) 3.0 ± 0.2 NaCAS 3%-CMC 0.75% (4:1) 3.4 ± 0.3

Table 3. Average pore sizes of NaCAS gels in the absence and presence of different

These results are consistent with the values of G'max (Table 2) obtained for the different

As CMC proportion rises, the aggregation and gel times of NaCAS:CMC mixtures increased and the pH at which these processes begin decreased, revealing a stabilizing effect of CMC. The degree of compactness diminished when the CMC proportion increased. This effect can be linked to protein conformational changes in the presence of CMC that lead to a decrease of surface hydrophobicity, which difficult the establishment of hydrophobic interactions.

Therefore, it is possible to obtain acid gels with different textures varying the protein:polysaccharide proportions due to surface hydrophobicity and electrostatic stability modification of NaCAS particles and due to changes on the kinetic of aggregation and

This work was supported by grants from the Universidad Nacional de Rosario. Thanks to MSc. Luis Martínez of the National University of Quilmes for their advice in the rheological measurements. Thanks to Prof. Mirta Armendariz of the National University of Rosario for their advice in the statistical analysis. The authors would like to thank Lic. Romina Ingrassia

NaCAS:CMC 2:1 failed to gel consistency.

concentrations of CMC, at 35ºC and R 1.

**4. Conclusion** 

gelation processes.

**5. Acknowledgment** 

for the English revision.

mixtures. Gels with larger pores will be less elastic.

The gels also showed lower elasticity at CMC:NaCAS high ratios.


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**7** 

*Romania* 

**Electrochemical Behaviour of AISI 304 Stainless** 

**Steel Immersed in Mixtures Consisting by** 

Maricica Stoica1, Petru Alexe1, Rodica Dinica2 and Geta Cârâc2

*1Dunarea de Jos University of Galati/ Department of Biochemistry and Technologies 2Dunarea de Jos University of Galati/ Department of Chemistry Physics and Environment* 

Chemical disinfection of industrial facilities in food bioprocessing is a major consumer of biocides and represents an essential technological issue. Due to this requirement, the metallic surfaces of the equipments used in bioprocessing inevitably interact with electrolyte environments that are exposed to washing and disinfecting solutions with or without microorganisms through on electrochemical mechanism (Landoulsi et al., 2008; Osarolube et al., 2008). Recently the electrochemical behaviour of stainless steel surfaces have become interested to the many researchers (Hiromoto & Hanawa, 2006; Stoica et al. 2010a). However, only a few research studies were devoted to the electrochemical behaviour of stainless steels used in bioprocesses having a synergic effect on biocides and microorganism (Stoica et al., 2009; Stoica et al., 2010b). The electroanalytical techniques used in previous studies through discharge of an electric field can generate some chemical and physical processes, reversible or irreversible because of the fungi present in the environments (Shen et al., 2008 ; Yang et al., 2008) and on metallic surfaces. These processes are strongly influenced by many factors, such as: biological factors (microorganisms type; cell wall; size and shape of the cell; cells density, arrangement and cell position, fluid medium properties in medium conductivity, electric field waveforms and the number of electric pulses (Yang et al., 2008 ). The complex phenomena occurring in the electrochemical biocide-fungi-metallic surface system are studied as electrochemical interface processes occurring at the limit between molecules of aqueous solution (biocide solution) coming into contact with the metallic electrode 'live' (fungal cell membranes) and the metallic surface (AISI 304 Stainless Steel). The electron transfer in these electrochemical systems respects the general laws of charge transfer, but also presents the specific properties based on the dynamic environment in which the electron transfer occurs, at the processes of adsorption/desorption and at the surface reactions. These can occur between molecules of biocide and biological surfaces as well as between biocide penetration through these surfaces endowed with distinct architecture, composition and characteristics. The study of these complex processes requires a multidisciplinary approach regarding the metallic surfaces, fungi, biocides and electrochemical processes interface. The aim of this chapter is to systematically present the relevant aspects about the interface electrochemical processes on metallic surfaces with fungi and biocides. A relevant study on the electrochemical behaviour of the AISI 304

**1. Introduction** 

**Biocide and Fungal Suspensions** 

