## 2 Materials and Methods
### Study by \({}^{1}h\) NMR of Oil Samples and Lipid Extracts of Digestates
#### 2.4.3 Quantifications from \({}^{1}\)H NMR Spectral Data  
This technique allows the estimation of the concentrations, expressed in different ways, of all of the aforementioned identified compounds. This is possible because, as explained, the area of the \({}^{1}\)H NMR signals is proportional to the number of protons that generate the signal. The quantification of the different kinds of compounds or structures is explained below. (A) Estimation of the Molar Percentage of the Different Kinds of Glycerides in the Digestates  
Estimations of the molar percentages of each kind of glyceride structure can be carried out by using the intensity of the signals indicated in Tables S2 and S3, which are also shown in Figure 1. Although glycerol is formed during digestion, due to its polar nature, it is not present in the lipid extract of the digestate; however, its concentration can be estimated indirectly. This is possible because the concentrations of total fatty acids plus acyl groups, of only acyl groups, and of fatty acids released in the formation of diglycerides and monoglycerides can be determined from the \({}^{1}\)H NMR data. Thus, the estimation of the molar percentage of triglycerides (TG), 1,2-diglycerides (1,2-DG), 1,3-diglycerides (1,3-DG), 2-monoglycerides (2-MG), 1-monoglycerides (1-MG), and glycerol (Gol) in relation to the  
Figure 1: Region between 0.0 and 4.9 ppm of flaxseed virgin oil, F, \({}^{1}\)H NMR spectrum, and enlargement of the region between 3.5 ppm and 5.10 ppm of the \({}^{1}\)H NMR of the lipid extracted from the digestate, DF. The signal letters agree with those of Tables S2 and S3 of Supplementary Material. total glyceryl structures present in the digestate was carried out using equations [Equations S1-S10] given in the Supplementary Material. They are based exclusively on the intensity of the \({}^{1}\)H NMR spectral signals [33]. Figure 2: (**A**) Chemical structures of the phenolic compounds involved in this study (gamma-tocopherol \(\gamma\)T, hydroxytyrosol acetate hydroxytyrosol acetate (HTA) and dodecyl gallate dodecyl gallate (DG), together with some chemical shifts (ppm) of the \({}^{1}\)H NMR signals of some of their hydrogen atoms. (**B**) Enlargement of some regions of the \({}^{1}\)H NMR spectra of nonenriched F and some enriched oil samples (FyT\({}_{2}\), FHTA\({}_{2}\) and FDG\({}_{2}\)), in which the signals of the aforementioned phenolic compounds appear. The signal letters agree with those of Table S5. (B) Estimation of the Molar Percentage of Fatty Acids Plus Acyl Groups that Have Linolenic Structure in Relation to the Total of All Types of Fatty Acids and Acyl Groups in Digestates  
In edible oils, the concentration of fatty acids is very small and, in many cases, inappreciable in comparison with the concentrations of acyl groups. However, during digestion, hydrolysis brings about the transformation of a certain number of acyl groups into fatty acids. The formed fatty acids maintain the same number of carbon atoms and unsaturation pattern as the starting acyl groups. Acyl groups and fatty acids having the same structure provide NMR spectra signals with a high degree of overlap that allows their joint quantification. In this study, the molar percentage of the linolenic acyl groups plus linolenic fatty acids in the digestates was estimated in relation to the total number of moles of all kinds of fatty acids plus acyl groups. This estimation was made using Equation S11, given in Supplementary Material, in which the areas of some signals that are shown in Figure 1 and in Table S3 are involved. This equation was employed in previous studies [22; 23], but using the signal of methylenic protons supported on carbon atoms in alpha position in relation to carbonyl-carboxyll groups, instead of the signal of triglyceride protons used in edible oil studies.