Ekmeğe Avokado İlavesinin Antioksidan Kapasite Ve İn Vitro Glisemik İndeks Üzerine Etkisi

Abstract

White bread, a primary energy source in Turkish society, is known to have a high glycemic index (GI) and low total phenolic content and antioxidant capacity. This study investigated the effects of substituting 5–10% avocado powder for wheat flour on the bread's chemical composition, total phenolic content determined by the Folin- Ciocalteu method, and antioxidant capacity assessed by 2,2′-azinobis-(3-ethylbenzothiazoline-6- sulfonic acid) (ABTS) and ferric reducing antioxidant power (FRAP) methods. In addition to the texture properties, color parameters, and starch digestibility of fresh breads obtained by baking at 200°C for 20 minutes, breads that were fully baked and stored frozen at –20°C for 7 days and breads produced by pre-baking at 170°C for 10 minutes, storing frozen at –20°C for 7 days and re-baking at 220°C for 11 minutes were evaluated. In vitro starch digestion was performed to obtain both starch fractions and estimated GI (tGI). In addition, scanning electron microscopy (SEM) analysis was performed to analyze the microstructure of the bread crumb. As a result of the analyses performed in triplicate, the protein and fat contents of the breads did not change significantly with avocado powder substitution, while the ash and dietary fiber contents increased significantly (p<0.05). With the substitution, the total phenolic content of bread per 100 g dry weight increased from 75.53±4.22 mg gallic acid equivalent (GAEq) to 123.67±10.99 mg GAEq; antioxidant capacity increased from 97.20±4.78 μmol Trolox equivalent (TEq) to 303.37±19.03 μmol TEq by the ABTS method and from 161.10±2.12 μmol TEq to 370.13±43.07 μmol TEq by the FRAP method (p<0.05). However, it was found that the substitution decreased the volume and specific volume in breads, caused darkening of the crust and crumb color, decreased the yellowness (bi) value in the crust, decreased the redness (ai) value in the bread, and increased the bi value (p<0.05). Furthermore, avocado powder substitution increased the hardness, gumminess, and chewiness of breads, while significantly decreasing the elasticity, cohesiveness, and springiness values (p<0.05). On the other hand, it caused a decrease in the level of rapidly digestible starch in fresh breads from 56.70±1.35% to 40.19±1.63% and an increase in the contents of slowly digestible and resistant starch from 34.28±0.47% to 44.14±1.33% and from 9.01±1.11% to 16.40±0.72%, respectively (p<0.05). These results were accompanied by a decrease in the tGI value from 94.61±0.53 to 83.95±0.30 (p<0.05). These potential benefits of avocado bread will contribute to the acceleration of positive human health. Future research should validate the nutritional benefits of this bread model through human studies and assess its clinical relevance.