Development of extraction methods to obtain high value-added products from illex argentinus and cynara scolymus

Resumo

This surges with the aim to contribute to the need to make a sustainable and responsible use of natural resources, much more considering their fast decline, exponential population growth and global climate change. The utilization of the vast organic material generated during food processes to obtain valuable bioactive compounds by non-aggressive treatments must be considered a priority, with both environmental and economic profit. This thesis focuses on one hand on the utilization of by-products from Illex argentinus, most heavily fished species of squid in the world, to obtain by mild chemical and more environmentally friendly enzymatic procedures, high yields of β-chitin and most important derivative, chitosan. These non-toxic, biodegradable and highly value-added products present unique characteristics in Nature and has countless applications in different industries. Optima conditions for chitin isolation were established at 0.82 M NaOH/36.4 ◦C, 57.5 ◦C/pH = 9.29, 59.6 ◦C/pH = 9.30 and 49.6 ◦C/pH = 5.91 for chemical, alcalase, esperase and neutrase deproteinization, respectively. The results in this study indicate the feasibility to obtain good yields of β-chitin by enzymatic treatments. Esperase was the most adequate enzyme to release protein from pens of I. argentinus and showed similar proteolysis capacity to alkalis, opening up the feasibility of using more environmentally friendly techniques without compromising good yields of resultant chitin. Moreover, the low interespecific variability of β-chitin content in squid pens and similar response to deproteinization treatments (Chandumpai et al., 2004; Lavall et al., 2008; Abdou et al., 2008; Arrouze et al., 2017), suggests the possibility to apply the same procedures presented in this study on by-products from other squid species. Chitin samples were subsequently deacetylated by alkaline treatment reaching the highest degrees of deacetylation (DD > 93%) at 61.0–63.7% of NaOH and 14.9–16.4 h of hydrolysis depending on the type of process previously performed to the squid pens. Molecular weight (as number average molecular weight, Mn) of chitosan produced in the experimental designs ranged from 143 kDa (PDI 2.37) to 339 kDa (PDI 2.38). The β-chitosan obtained in this study can find applications in the food, cosmetic and biomedical industries, amongst others. On the other hand, this thesis assesses the utilization of Cynara scolymus by-products, vegetable with the highest antioxidant activity in the Mediterranean diet and yet, highest degree of underutilization during its industrial processing. The recovery of, among other bioactive molecules, polyphenolic compounds conferring its antioxidant activity and many other health-benefitting properties was conducted by means of food-grade solvents and mild extracting conditions, and subsequently concentrated by equally environmentally friendly novel CGAs flotation techniques. First extraction was conducted with ethanol:water solutions at concentrations: 25 - 100% ethanol, temperatures: 30°C - 60°C and times of extraction: 10 - 60 minutes. Best results were achieved at 75% EtOH/40°C/10 min, obtaining 21,56 g GAE/100g of total phenolic content (TPC) and 55472,34 µmol TE/100g of antioxidant capacity (AOC). Concentration of solvent was by far the parameter with the greatest impact on the obtaining of polyphenols and antioxidant activity displayed, followed by temperature. Time of extraction did not present a strong impact on the extraction of these compounds nor the antioxidant capacity displayed by the extracts. The correlation between TPC and AOC of the extracts was significant at all the conditions studied. HPLC and MS-MC chromatographic analyses determined the polyphenolic profile of the resultant extracts consists mainly of mono and di-caffeoylquinic acids. The extracts presented thermal stability at 4°C, 20°C - stated as room temperature - and 37°C, for a time of up to 3 months in terms of inulin content, TPC and AOC displayed. techniques were successfully used in order to recover polyphenols with antioxidant activity from a hydroalcoholic extract of artichoke by-products. The separation of polyphenols is driven by hydrophobic and electrostatic forces. High volumetric ratios CGAs:Feed showed more efficient in terms of mass recovery and concentration of the molecules studied, as well as antioxidant activity gain from initial extract, whilst a clear decrease was observed at low volumetric ratios. This was particularly evident with the use of CGAs generated with CTAB, whose affinity for proteins and sugars was superior to that of Tween 20. The efficiency in terms of mass and concentration differ due to the resulting different volumes of CGAs fractions generated from each surfactant. The results from these studies show the feasibility to obtain high value-added products from industrial discards and by-products from Illex argentinus and Cynara scolymus by environmentally friendly extracting conditions, to be applied in a large number of industries. Te application of these techniques at the industry level would imply environmental and potential economic benefits.