Nanofluids and nutritional value

Pasteurizing with nanofluids in order to preserve the nutritional value of tomato juice

Nanofluids are a new class of heat transferring fluids that use nanotechnologies, and are obtained by dispersing and stabilizing nanoparticles that improve the thermal properties of liquids. Researchers at Iran's Azad Islamic University have demonstrated that using nanofluids as pasteurizing agents can improve the nutritional value of tomato juice. 

"In this research, we wanted to test a thermal process that uses nanofluids instead of conventional pasteurization processes, in the hope of reducing the duration of thermal treatments and improving the nutritional value of fruit juices, in particular of tomato juice," explained the researchers. 

Three different variables were considered: temperature (70°C, 80°C and 90°C), the concentration of nanofluids (alumina nanoparticles with a purity level of 99%, at concentrations of 0%, 2% and 4%) and the duration of thermal treatment (30 seconds, 60 seconds and 90 seconds).
 
Results showed that a 30 second thermal treatment with a 4% concentration in nanofluids at 70°C preserved the concentration of vitamin C (a particularly thermolabile component) at about 66% of its initial concentration in fresh juice, whereas when tomato juice is treated with a minimal concentration of nanofluids at 90°C for 90 seconds, only 56% of the vitamin C is preserved.

Thanks to this improvement in the heat transfer process, the higher concentrations of nanoparticles reduced the duration of the heat treatment needed to prepare the juice, and phenolic compounds were globally better preserved than with conventional pasteurization. After 30 seconds of thermal treatment at 70°C with a 4% concentration of nanoparticles, total phenolic compounds were preserved at 74% of their original level, with a Brix of 5.4 to 5.6, which means that thermal treatment with nanofluids could represent a better method for preserving the natural composition of tomato juice. 

In their conclusions, the researchers explain that higher nanoparticle concentrations and lower temperature or time result in higher vitamin C contents, with a vitamin C concentration of about 262.143 mg/kg attained at this state. All three variables have significant effects on the Total Phenolic Compounds response. 

By following total soluble solids (TSS) changes at different nanoparticle concentrations, it could be recognized that increasing the concentration of nanoparticles can result in lowering TSS contents, although the changes in TSS according to the differences in variables are really restricted.

These findings, for the first time, demonstrate that nanofluid thermal technology could be deployed for improving the nutritional contents of food products significantly and successfully. It seems that other nanoparticle concentrations and types should be tested in the same way for their probable effects on thermal properties and qualitative indices of food products, in order to realize the highest possible improvements in these properties. 

Source: "Effects of thermal processing by nanofluids on vitamin C, total phenolics and total soluble solids of tomato juice", (S. M. Jafari, S. S. Jabari, D. Dehnad, and S. A. Shahidi), 2017, Journal of Food Science and Technology, Volume 54, Number 3, Page 679-686.

For further details: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5334226/