# Effects of Heat Treatment Processes: Health Benefits and Risks to the Consumer
## 4 Lipid Content  
S seaweeds contain fats in the form of saturated fatty acids (SFA) such as myristic acid, palmitic acid and stearic acid; monounsaturated fatty acids (MUFAs) such as oleic acid, palmitoleic acid and eicosenic acid; and polyunsaturated fatty acids (PUFAs), such as linoleic acid, stearidonic acid, arachidonic acid and eicosenetanoic acid, representing approximately 40% of the total fat/lipid content [11; 20]. In regard to PUFA, some are considered essential fatty acids because they cannot be biosynthesized by the human body and are solely obtained through the diet. The beneficial impacts and properties of these lipidic compounds is well studied, and it is important to understand the variation in these fatty acids when exposed to heat treatment. For _S. latissima_ (Phaeophyceae), there was no significant difference in the lipidic content in [20] when dried under the temperature and humidity conditions tested in the study (30 \({}^{\circ}\)C, 50 \({}^{\circ}\)C and 70 \({}^{\circ}\)C temperature and 25-50% humidity). This could mean that under heat treatment, there is no loss of lipids through dripping or oxidation [20]. However, for _Pyropia orbicularis_ (Rhodophyta), fatty acid concentration was observed to suffer modifications according to the drying method applied [13]. While there was a yield loss of SFA for sun-drying and oven-drying compared with freeze or vacuum-drying, there was no significant difference in total MUFA content with different drying techniques [13]. Interestingly, for these algae, a higher decrease in PUFA content was reported for samples treated with freeze-drying and vacuum-drying, compared with sun- or convective drying. For _F. spiralis_, _F. serratus_, _H. siliquosa_ and _P. canaliculata_, the highest lipid content values tended to be obtained through freeze-drying, while for _L. digitata_, they were obtained through oven-drying at 40 \({}^{\circ}\)C, and the lowest value of lipid content was identified for both _Fucus_ species in oven-dried batches. C16:0, C18:1 and C20:4n6 were the predominant SFA, MUFA and PUFA for all seaweeds, respectively. For SFAs, higher levels were found in _L. digitata_ and _H. siliquosa_ after freeze-drying and oven-drying and 40 \({}^{\circ}\)C, while other species showed little differences in SFA content. MUFA content was the highest in _F. spiralis_ and _L. digitata_ after oven-drying at 40 \({}^{\circ}\)C, followedby freeze-drying and microwave treatment at 385 W. Regarding PUFA levels, _L. digitata_ and _H. siliquosa_ exhibited higher concentrations after microwave treatment, while both _Fucus_ species had higher levels after freeze-drying [11]. The lipid content in _Aspargopsis taxiformis_[9] when exposed to oven-drying (60 \({}^{\circ}\)C) or freeze-drying also demonstrated important changes. Overall, total lipid yield for _A. taxiformis_ was low, with slightly higher lipid preservation in freeze-dried samples. The fatty acid profile (as a percentage of total fatty acids) was characterized by a high concentration of saturated FAs (76% of total FA), with low levels of monounsaturated fatty acids (4-11% MUFAs) and even lower concentration of polyunsaturated fatty acids (0-11% PUFAs) after drying. In _A. taxiformis_, a relative higher concentration of SFA and MUFAs was obtained through oven-drying at 60 \({}^{\circ}\)C, with the exception of PUFAs, which demonstrated a higher concentration in freeze-dried samples [9]. Overall, there have been several results regarding total fatty acids concentrations, a variation that may have resulted from the method applied or due to the intrinsic variation between algae species. During the drying processes, oxidation and degradation of lipidic content can occur via several mechanisms, such as autoxidation, photosensitized or enzymatic reactions. In the case of PUFAs, autoxidation is specially critical, due to the intrinsic low disassociation energy [11; 20].