Production of leathers based on carrot residue puree using the tape-casting technique

In Brazil, the generation of organic waste represents half of the total urban solid waste. The large volume of plant residues (industrial, food and residential establishments) is generated daily, causing economic and nutritional losses and environmental impacts. These residues, in general, have a high concentration of nutrients and can be used to develop products with high nutritional value. Snacks are widely consumed due to their practicality; however, the majority have a high caloric value and various additives that can affect health. In this way, the production of snacks from vegetable residues puree can contribute to the reduction of the generation of organic residues, increase the consumption of vegetables and, at the same time, offer to consumers a quick, nutritious, and low-calorie meal option. In this context, the objective of this study was the production of leathers-type snacks based on carrots residue discarded due to physical injuries (which make the product unattractive to the consumer) in supermarkets. The residues (peels) were used to produce the carrot residue puree (CRP) and leathers were produced using the tape-casting technique with different concentrations of CRP (40 and 60 g CRP/100 g leather forming mass (LFM)) and agar-agar (2 g/100 g LFM). A spreader ZAA 2300 (Zehntner Testing Instruments) was used to produce the leathers, with an adjustable applicator (TKB Erichsen, APF 01/20) (thickness of 4 mm), and dried in an oven at 50 °C for 9 hours. Leathers were characterized in terms of water content (WC), strength and strain at break, total phenolic compounds (TPC), total carotenoids (TC) and antioxidant activity (FRAP and ABTS•+). Leathers (regardless of CRP concentration) have a uniform matrix and are easy to handle, with WC ranging from 8.15±0.59 to 8.64±0.71 g/100 g dry basis (db). The increase of the concentration of CRP had no effect (p>0.05) on the breaking strength (15.06±2.23 to 15.86±2.47 N). The strain at break increased (p<0.05) in the function of the higher concentration of CRP, being 2.05±0.30% for leather with 60 g CRP/100 g LFM. The higher fracture strength may be associated with interactions between the macromolecule matrix and water, in which the matrix deforms before breaking. Leathers with 60 g CRP/100 g LFM showed higher concentrations of TPC (251.08±28.48 mg gallic acid equivalent/100 g db) and TC (9.34±0.86 mg/100 g db), in addition to higher antioxidant capacity by FRAP methods (66.65±9.69 µmol trolox equivalent/100 g db) and ABTS•+ (1,009.13±115.69 µmol trolox equivalent/100 g db). The production of leathers with higher concentrations of CRP, as expected, can improve the nutritional value of these products. The production of leathers from carrot production waste is a technological and sustainable way to reuse food waste and can contribute to reducing the generation of organic waste.