Ammonium acetate

Hydrochloric acid, acetic acid, methanol, sodium carbonate, iron chloride, ammonium acetate and Folin–Ciocalteu reagent were purchased from the manufacturer Kemika (Zagreb, Croatia). Trolox was purchased from Sigma (Darmstadt, Germany). 2,2’-azinobis (3-ethylbenzothiozolinesulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were purchased from Fluka (Darmstadt, Germany). 2,4,6,-tri (2-pyridyl)-s-triazine (TPTZ), gallic acid, procyanidin B2 and myrtenol were purchased from Sigma, Germany. Neocuproine and copper chloride are products of Gram-mol Zagreb, Croatia). Sucrose was purchased from Gram-mol (Zagreb, Croatia), and maltose and trehalose were obtained from Hayashibara doo (Nagase group, Tokyo, Japan). Citrus fibers were obtained from Biesterfeld AG (Zagreb, Croatia).

Trolox, 2,4,6,-tri (2-pyridyl)-s-triazine (TPTZ), gallic acid, procyanidin B2 and myrtenol were purchased from Sigma-Aldrich (St. Louis, MO, USA). Hydrochloric acid, acetic acid, methanol, sodium carbonate, iron chloride, ammonium acetate and Folin-Ciocalteu reagent were purchased from Kemika (Zagreb, Croatia). 2,2′-azinobis (3-ethylbenzothiozolinesulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were purchased from Fluka (Buchs, Switzerland). Neocuproine and copper chloride were obtained from Gram-mol (Zagreb, Croatia). Sucrose was purchased from Gram-mol (Zagreb, Croatia), while trehalose was obtained from Hayashibara doo (Okayama, Japan). Citrus fibers were obtained from Biesterfeld AG (Zagreb, Croatia).

High molecular weight chitosan (CH) (acetylation degree ≥ 75%, 310–375 kDa), lactic acid (LA) (purity ≥ 85%), and tannic acid (TA) were purchased from Sigma-Aldrich (Steinheim, Germany), while methanol and acetonitrile were purchased from Avantor Performance Materials (Gliwice, Poland) and Honeywell (Hannover, Germany), respectively. Sodium dihydrogen phosphate dihydrate and ortho-phosphoric acid (purity ≥ 85%) were obtained from Merck (Darmstadt, Germany), ammonium acetate from Kemika (Zagreb, Croatia), and glycerol (GLY) from Pharmachem Sušnik (Ljubljana, Slovenia). Commercially available CE (≥75% tannins; <4% of ash) was provided by the company Tanin Sevnica (Sevnica, Slovenia). All chemicals except LA were of analytical grade. According to EU legislations (EU) 2017/2470 (chitosan) 2017, (EU) 2017/66 (tannic acid) 2016, (EU) no 231/2012 (lactic acid and glycerol) 2012 [30 ] chestnut extract specification (provided by producer company), all the substances can be considered as food additives. Milli-Q^® water was used throughout all the experiments.