## 3 Results
Columns label interpretation: (i) lowercase letters indicate differences among enzymes for the ratio 1/20 and for the <3000 Da fraction; (ii) different uppercase letters indicate differences among enzymes for the ratio 1/20 and for the fraction >3000 Da; (iii) different Greek letters indicate differences among enzymes for the ratio 1/50 and for the <3000 Da fraction; (iv) different numbers indicate differences among enzymes for the ratio 1/50 and for the-> 3000 Da fraction; (v) different symbols indicate differences between the ratios 1/20 and 1/50, for each fraction. Highest concentration of free amino acids, ca. 45 mg/L, was found with the use of collagenase at the 1/50 ratio; globally, by the 1/50 ratio a high concentration of free amino acid was observed for the three enzymes used (Table 3). The concentration of each amino acid also varied according to the enzyme and to the E:C ratio; nonetheless, whatever the enzyme and the ratio, major free amino acids found were glutamine, glycine and glutamic acid. With the ratio 1/50 significant higher amounts of lysine and hydroxylysine were found by the three enzymes used; when using collagenase a significant higher amount of proline and methionine was also found. Either enzymes or E:C ratio did not have a noticeable effect on calcium and magnesium content although some values were statistically different. Concentration of Ca\({}^{2+}\) was in the order 3860-4066 mg/L, and 220-255 mg/L for Mg\({}^{2+}\) (Figure 2). All the calcium passed in the <3000 Da fraction through filtration; for magnesium the highest amount passed in the <3000 Da however it was also found in the >3000 Da (50-160 mg/L), and in particular in the collagenase and cathepsin hydrolysates. Depending on the enzyme, concentration of calcium was 21-29-fold higher than peptides; concentration of peptides was in the same order of magnesium concentration. Regarding phosphorous, by the FTIR analysis it was possible to determine that it was present (Figure 3). As expected, tri-calcium phosphate, Ca\({}_{3}\)(PO\({}_{4}\))\({}_{2}\) (picks at the frequencies 1156, 1076, 1017 and 990 cm\({}^{-1}\), Figure 3) was predominant accounting for 75% of the total phosphates' integration area; di-calcium phosphate, CaHPO\({}_{4}\) (pick at 937 cm\({}^{-1}\), Figure 3), was also found and accounting for 25% of the total phosphate's integration area. Hence, the concentration of phosphorous, stoichiometrically calculated from the concentration of calcium, was estimated to be 2300-2350 mg/L for all the <3000 Da fractions. Figure 2: Calcium and magnesium content in the solutions (Bro. = bromelin, Col. = collagenase B, Cat. = cathepsin B) ((**a**) < 3000 Da and (**b**) > 3000 Da) according to the enzyme used and the enzyme:collagen ratio (mean \(\pm\) standard deviation). Different uppercase letters above columns indicate statistical differences among values (\(p<0.05\)). Figure 4: Percentage of inhibition of the ABTS\(\bullet^{+}\) by the peptides-minerals complexes, for the <3000 Da fraction and for the ratio E:C 1/20 (**a**) and 1:50 (**b**); for the <3000 Da fraction, E:C 1/20, after sterilization (**c**); for the <3000 Da fraction, E:C 1/20, after 3-folds concentration (**d**). Columns label interpretation: (i) different uppercase letters indicate differences over time for complexes obtained by bromelain; (ii) different lowercase letters indicate differences over time for complexes obtained by collagenase B; (iii) different Greek letters indicate differences over time for complexes obtained by cathepsin B; (iv) different symbols indicate differences among peptide-mineral complexes according to the enzyme.