Improving the Rheological Properties of Dough Obtained by Partial Substitution of Wheat Flour with Freeze-Dried Olive Pomace

Abstract

Mediterranean countries are known for their high-quality olives and the production and consumption of olive oil. Olive pomace (OP), the major by-product of olive oil extraction, is receiving attention for its potential as a functional compound in food products, reflecting its physiology- and health-promoting attributes. This study assessed the physico-chemical characteristics of OP obtained from two Sardinian olive cultivars, Bosana and Semidana, and the effect of OP incorporation on the baking performance of wheat dough. We assessed the rheological parameters, pasting profile, and fermentation of doughs obtained through the partial substitution of wheat flour with OP at 0 (control), 1, 2, 3, and 5%. OP inclusion resulted in significant differences in the studied parameters compared with control samples. Positive effects included a decrease in development time, improved dough stability and storage, and superior loss modulus and gas retention capacity. Negative effects comprised an increase in dough resistance and a decrease in dough development height, gas production, gas retention, pasting profile, stickiness, and elasticity. These differences in the OP dough were due to the interactions between polyphenols and fibre with water and the starch–gluten matrix. This study found improvements in dough characteristics following the substitution of wheat flour with low percentages of OP, especially Semidana at 1%. Although higher percentages of OP would be associated with greater nutritional and health benefits, they resulted in a degradation of the dough’s attributes, producing a gluten-free-like matrix in the final product.

Innovations in Wheat Bread: Using Food Industry By-Products for Better Quality and Nutrition

“…The increase in dough stability and decrease in softening degree can be attributed to the hydroxyl groups present in phenolic compounds, which can directly bond with wheat flour proteins and affect the functional properties of the food. The study by Dahdah et al [72], on the other hand, showed a decrease in dough development time and dough stability with increasing olive pomace content. However, at low supplementation levels (1-3%, depending on the olive variety), the changes in dough stability were insignificant compared to the control sample.…”

“…This decrease was mainly attributed to gluten dilution, requiring lower amounts of water to achieve the optimal consistency, and the higher content of oil, which can coat both starch and gluten, leading to a reduction in water absorption. In the study conducted by Dahdah et al [72], a reduction in water absorption was noted as the supplementation levels of olive pomace increased, particularly with additions exceeding 2%. They utilized freeze-dried powder (<500 µm) obtained from olive pomace (from two olive cultivars) to supplement wheat flour.…”

“…During olive oil production, the quantity of olive pomace generated varies from 2.75 to 4 tons per ton of oil, influenced by fruit quality and extraction technology [13,70]. Olive pomace stands as a significant by-product in the olive oil industry, making up roughly 65% of the initial weight of pressed olives in a three-phased pressing system or 80% in a two-phased decanter [71,72]. Olive pomace encompasses pulp, skin, seeds, and stone fragments and has a high moisture content ranging from 65-75% [13].…”

“…Water absorption, in the context of dough preparation, denotes the quantity of water necessary to attain the desired consistency. This parameter is influenced by various factors such as the starch, damaged starch, protein, pentosan content, and the gluten network within the dough [72]. By-products like fruit pomaces and oil cakes, rich in dietary fiber and containing numerous hydroxyl groups in their structure, tend to form hydrogen bonds with water.…”