Orange pomace used in gluten-free bread. Photo: TeagascDuring the processing of fruit and vegetables one third is discarded as “waste.” The waste or byproduct can be described as the core, pips and peel of the fruit or vegetable. This waste can be costly for the manufacturer to dispose of and it may also have hazardous effects on the environment.

Research has shown that a high quantity of nutrients such as dietary fiber and bio-actives are present in these byproducts, thus the full potential of the fruit or vegetable is not fulfilled. For example, orange pomace, a byproduct from the smoothie and juice industry, has proven to have good nutritional attributes; it is low in fat (2% dry matter) and high in dietary fiber (40% dry matter) and has the potential to be used as a food ingredient.

Researchers at Teagasc Food Research Centre and Univ. College Cork have been looking in to possible uses for this discard—for example as orange flour in gluten-free bread formulations.

Presently in Ireland, approximately one in a hundred people suffer from coeliac disease. Coeliac disease can be explained as an autoimmune reaction to the prolamin fraction of the gluten protein, which causes damage to the villi in the small intestine. The only treatment for coeliac disease is lifelong avoidance of foods containing wheat, barley, spelt, rye and some oats. Many gluten-free products available on the market are calorie-dense, lacking in flavor, mouthfeel and nutrients, and are costly.

Gluten-free formulations

Eimear Gallagher, Teagasc Food Research Centre, explains: “Developing gluten-free formulations can be challenging for the cereal technologist, as the structure-building protein (i.e., gluten) is absent. In the present study, a response surface design was created to statistically calculate the optimal level of orange pomace addition, water addition and ideal proofing time to produce an optimal bread formulation. This study investigated the effects of these three factors in different combinations on bread parameters such as loaf volume, crumb structure, crumb color, texture, microstructure, nutritional and sensory properties and the optimized samples were assessed using sensory panelists.”

“Sensory panelists scored the bread favorably with respect to appearance, flavor, texture and overall acceptability,” says Norah O’Shea, a PhD student of Gallagher.

“The inclusion of orange pomace as a novel structure-building and nutritious ingredient in a gluten-free formulation was illustrated in this study. Using response surface methodology as a tool, successfully created bread with favorable baking characteristics and enhanced dietary fiber. Orange pomace proved to be a viable, low cost food by-product for improving the physical and nutritional characteristics of gluten-free breads,” says Gallagher.

“The addition of this ingredient is not limited to gluten-free bread; it has potential to be used in both gluten-containing and gluten-free breads and confectionary,” adds Gallagher.