**6.2 Carotenoids reduce lipid viscosity** *in vitro* **and** *in vivo*

The formation of complexes between carotenoids and lipids resulted in the reduction of their viscosity. Plant oils response was more significant than the animal fats. For example, one molecule of lycopene added to about 67,000 molecules of olive oil

#### **Figure 2.**

*Carotenoids reduce viscosity of lipids in vitro top slides and in vivo bottom slides. Viscosity was measured as a diameter, y-axis in μm, of a single drop of the oil on the surface of the water (a) or a single drop of the molten butter on the hard surface (b) at 37°C, before the experiment the butter and oil samples were warmed to that temperature too; x-axis—lycopene concentration in μ/g; each column is an average of three independent measurements. The microscopy of typical skin smear samples from 60-year-old clinically healthy man, collected before and 4 weeks after supplementation with 7 mg of highly bioavailable GA lycopene [5].*

lipids could reduce viscosity of the oil, in terms of its drops spreadability, by 10-fold, or 1000%; when it was added to about a similar amount of dairy fat lipid molecules, the reduction of the viscosity was only by 50% (**Figure 2a** and **b**).

Carotenoids could change the viscosity of lipids not only when they were incorporated in their matrix *in vitro*, but *in vivo* as well. For example, when middle-aged persons, who were clinically healthy but had age-associated lycopene functional deficiency, were supplemented with this carotenoid for 4 weeks, the viscosity of their sebum, in terms of the diameters of the lipid droplets collected from the surface of the skin, was significantly increased (**Figure 2**, two slides on the bottom-right). The fact that these changes were not just associated with the lycopene intake but caused by its accumulating in these droplets was confirmed by the direct measurement of this carotenoid in the collected sebum (**Figure 2**, two slides on bottom-left).

## **6.3 Carotenoids increase thermal energy absorption, heat storage capacity, heat retention and thermoconductivity of lipids**

The incorporation of carotenoids into plant or animal lipids increases their rate of thermal energy absorption, the amount and the time of this energy storage. For example in **Figure 3**, when the same level of heat was applied, the sunflower oil with carotenoids could start to accumulate this heat faster and become hotter by 5°C, and after the external heat was switched off, the retention of the heat lasted significantly longer.

The increase in lipid thermoconductivity by carotenoids was demonstrated in another set of experiments. For oils, liquid at room temperature, we froze them first and then measured this parameter in terms of time, which was necessary to defrost these oils. For lipids, solid at room temperature, we assessed thermoconductivity as a time, which was necessary to melt them at +37°C. In these experiments, carotenoid increase in thermoconductivity was more prominent in plant oils than in animal fats.

For example, the same concentration of lycopene, 330 μg/mL, could reduce the defrosting time of the olive oil by 12-fold, but the cod liver oil only by twofold (**Figure 4a** and **b**).

For lipids, solid at room temperature, the same as in above experiments, the concentration of lycopene could increase the melting time of cocoa butter by more than 10-fold, but for dairy fat by only threefold (**Figure 4c** and **d**).

This increase in thermoconductivity could also be observed in the heating not just in lipids but in their emulsions in water too. For example, lycopene in concentration

#### **Figure 3.**

*Carotenoids increase the heat storage capacity of sunflower oil. Vertical axis—temperature t °C/mL, horizontal axis—time of the experiment, in min; blue—control oil, green—with 9.3-μM lycopene, purple—with 9.3-μM β-carotene, red—with18.6-μM astaxanthin.*

*Carotenoids in Thermal Adaptation of Plants and Animals DOI: http://dx.doi.org/10.5772/intechopen.104537*

#### **Figure 4.**

*Carotenoids increase thermal energy conductivity in different lipids and their emulsions. OO—olive oil, other abbreviations as in* **Figure 1***. \*Defrosting time from –30°C of frozen oils to room temperature, x-axis—lycopene concentration in μg/mL; in kerosene, astaxanthin and lycopene concentrations were 16μg/mL. \*\*Melting time at +37°C to room temperature, x-axis in this and the following experiment—lycopene concentration in μg/g. \*\*\*Boling was at +350°C; in all the above experiments, y-axis is time in seconds, and each column is an average of three independent measurements. Kinetics of heating of OO-in-water emulsion, at heated 150°C stove, y-axis temperature in °C, x-axis—time in seconds, blue line—control, red—with lycopene in 230 μg/mL.*

of 330 μg/g could accelerate the time to reach the boiling point for dairy butter by fourfold (**Figure 4e**). In another experiment, to reach a temperature from 20°C to +45°C for 50:50 olive-oil-in-water emulsion, with the same carotenoid in concentration of 230 μg/mL, took only 3 min, when for the control emulsion, it was 7 min. Moreover, carotenoids were not just able to increase the rate of heating but the maximum level of the temperature the emulsions could reach. In this particular experiment, the increase was by 14°C, from 51°C for the control emulsion to 65°C when lycopene was therein (**Figure 4f**).
