Application of emerging cryoprotectants in frozen food

Abstract

Freezing is an extremely useful food preservation technique, as it allows you to store products for a long period. Despite its benefits, freezing can cause structural damage to products of animal and vegetable origin, due to the formation of ice crystals. The mechanical damage caused by them can favor lipid and protein oxidation, in addition to promoting loss of texture, loss of water and water-soluble compounds during defrosting. To reduce this damage to frozen foods, cryoprotective agents can be used. In this context, the present thesis aims to evaluate the cryoprotective potential of cellulose nanofibers (CNF) and gelatin hydrolysate (GH) and analyze the impacts of the addition of these compounds on the physicochemical and microstructural characteristics of foods of plant and animal origin. The work was divided into two articles. In the first article, the combined cryoprotective potential of different concentrations of CNF (0.08 to 4.32 % m/m) and GH (0.08 to 4.32 % m/m) impregnated on frozen potato sticks was evaluated. In this article it was presented that the impregnating solution containing 2.20 % m/m of CNF and 2.20 % m/m of GH is effective in potatoes with lower losses of cellular fluids during thawing (19.06 ± 0.51 % and 28.71 ± 0.21 %, respectively) and change in texture (23.30 ± 0.54 % and 41.95 ± 0.55 %, respectively) when subjected to freezing with and without temperature fluctuation. This treatment showed reduced microstructural and color losses when compared to the control sample (free of cryoprotectants). In the second article, different concentrations of CNF (2, 4 and 6 % m/m) were evaluated in surimi-like chicken, in addition to a positive control containing commercial cryoprotectants (sucrose, sorbitol and sodium tripolyphosphate) and a negative control free of cryoprotectants. Lower protein oxidation was observed in the surimi-like containing 2 % m/m of CNF in relation to the negative control and other treatments containing CNF, evidenced by the high concentration of salt-soluble proteins (9.62 ± 1.13 mg/g), lower protein carbonylation (1.85 ± 0.27 nmol/mg) and few changes in the secondary structure of myofibrillar proteins. The surimi-like added with 2 % m/m of CNF showed lower water losses due to thawing (6.12 ± 0.21 %) and cooking (30.24 ± 2.20 %) generating gels with high water retention capacity water (86.78 ± 1.56 %) and chewiness, and more homogeneous microstructure. In both studies, the results indicated that GH and CNF have effective potential for food cryopreservation.