Enrichment of White Wheat Bread with Pistachio Hulls and Grape Seeds: Effect on Bread Quality Characteristics

Featured Application Pistachio hulls and grape seeds are useful by-products of the pistachio and wine industries, respectively. Pistachio hulls and grape seeds can be used as alternative functional ingredients in wheat bread due to their high dietary fiber content and richness in antioxidants and phenolic substances. In this study, the effects of pistachio hulls (fresh and freeze-dried) and grape seeds (fresh and freeze-dried) on bread quality were compared in the 0.5-4% range of addition. In creating sustainable food systems, alternative uses of food waste and by-products as a source of phenolic compounds or dietary fiber in food formulations should be evaluated to reduce food losses and waste. In this study, wheat bread was fortified with agro-industrial by-products, namely, fresh pistachio hull (FPH), pistachio hull powder (PHP), fresh grape seeds (FGS), and grape seed powder (GSP), at different levels (0.5-4%). The effects of this enrichment on moisture content, crust and crumb color, specific volume, baking loss, total phenolic content, antioxidant activity, and textural properties were evaluated and compared with control bread. Fortification with pistachio hulls and grape seeds, especially in powdered form, improved the total phenolic content and antioxidant activity of the bread compared with the control bread. With the increase in the amount of PHP from 0 to 4.0%, the total phenolic content of the bread initially increased from 0.89 to 14.66 mg GAE/g dry weight and the specific volume decreased from 3.59 cm(3)/g to 2.91 cm(3)/g. Bread containing PHP showed a significant reduction in baking loss and specific volume, while the addition of FGS and GSP at a low level (0.5%) improved the specific volume. The brightness (L*) of the crumb and crust gradually decreased with increasing levels of all additives. The crumbs of the breads with PHP and FPH were characterized by lower hardness, while GSP and especially FGS had higher hardness. All enriched breads (except those with FGS) were more elastic and easier to chew.

Automated summary

This study compared the effects of fresh and freeze-dried pistachio hulls and grape seeds on bread quality at different addition levels. Addition of pistachio hulls and grape seeds improved the total phenolic content and antioxidant activity of the bread, especially in powdered form. However, it also affected the volume and hardness of the bread.