Avaliação do escurecimento enzimático em maçãs híbridas: potencial tecnológico e atividade antioxidante

Abstract

Apples and their products are important sources of phenolic compounds. When in contact with oxygen, the contents of these compounds, as well as their antioxidant activity, are reduced due to the action of two main enzymes, Polyphenoloxidase (PPO) and Peroxidase (POD), occurring the phenomenon of enzymatic browning. However, there are cultivars of apples from genetic improvements that, even after oxidative stress, have a low browning. The objective of this work was to evaluate the enzymatic browning in apples, with the purpose of investigating the low occurrence of this phenomenon in hybrid cultivars and to evaluate the technological potential of the fruits and their juices. Sixteen (16) apple varieties, among them seven (7) commercial and nine (9) hybrids (derived from the genetic crossing of the cultivars Imperatriz and Primícia), were evaluated in relation to the enzymatic browning. For this, the parameters Chroma, Hue angle and browning index were determined. In the whole fruit, the activity of the PPO and POD , ascorbic acid content and the test of their effectiveness, besides the quantification of the main individual phenolic compounds were determined. For intact fruits and their respective juices, total phenolic and total flavonoid contents were evaluated, as well as their antioxidant activity by DPPH, FRAP and ABTS methods. Physicochemical analyses of pH, titratable total acidity and soluble solids were made in the juices of all fruits studied. Hybrid apples coded as 170/23 and 170/25 obtained the lowest pulp darkening indexes (78.63 and 57.58, respectively), as well as in their juices (4.8 and 4.4, in that order). The cultivars Gala and Maxi Gala presented higher pulp browning (114 and 218, respectively), as well as for the respective juices, with a mean browning index of 384.5. Hybrid apples 170/23 and 170/25 also had lower enzymatic activity, corresponding to the seven commercial cultivars of more expressive browning, only 19% of PPO and 2.3% of POD activities, respectively. In determining the ascorbic acid content, these two cultivars also stood out with the highest levels: 29.95 mg / 100g for 170/25 and 16.57 mg / 100g for 170/23. However, ascorbic acid slows down the enzymatic action in a time interval, after this, it loses its effectiveness due to its saturation in the oxidized form. In relation to the physical-chemical analyses of juices, the results between commercial and hybrid fruits were similar among themselves. As for the phenolic analyses, the total phenol content for the nine hybrid cultivars ranged from 2902- 4966 mgEAC / kg for the fruit and 568-1264.3 mgEAC / L for the juices. For total flavonoids, the contents ranged from 1222-3319 mgECAT / kg for the fruit and 76.7-277.6 mgECAT / L for the juice. The fruits 170/23 and 170/25 obtained the lowest results for both the phenolic contents and the antioxidant activity. As for the hybrid fruits phenolic profile, the main compounds also present in commercial fruits were quantified. However, the main substrate related to enzymatic oxidation and formation of brown pigments, chlorogenic acid, presented one of the highest levels in the hybrid 170/25. The propagation of the characteristics of late enzymatic browning to future commercial cultivars can potentiate the market of minimally processed and whole juices. In addition, with the preservation of the phenolic compounds and their antioxidant capacity, there is the conservation of the functional and sensorial characteristics of the apple and its products.