Yesterday's ingredients could play a valuable role in tomorrow's bakery

Written by: Rita Beltrão Martins, Co-founder of Terrius Cristina Rosell, Professor and Head, Department of Food and Human Nutritional Sciences, University of Manitoba

Meeting the expected growth in food demand by 2050 has been one of the biggest challenges for agri-food sector stakeholders, further complicated by the scarcity of global resources and climate change.

Additionally, the political climate has been under enormous pressure with the world seeing more than two years of pandemic and the resurgence of war in Europe. Cereals, in particular, as basic commodities of the human diet, are expected to suffer tighter constraints due to the effects of climate change and their relatively high consumption worldwide. As a consequence, there is now an urgent need to find alternative flours that could be used for bakery products and in particular those that decrease our dependence on traditional cereals.

Looking back into days gone by, during the Roman Era, the scarcity of cereals gave rise to the development of bread with alternative flours such as those derived from acorn, carob, rye, herbs, legume seeds, straw and even dried animal's blood.

Similarly, the present-day grain crisis and food security concerns are driving a burgeoning interest in these previously underexploited crops, some of which potentially may contain excellent health benefits. Other raw materials, such as fruit and vegetables have been recognised for their health benefits due to their rich nutritional profiles, high bioactive compound content and potential antioxidant capacity. Underexploited raw materials like this, not only have the advantage of adding value to otherwise wasted resources, but also allow the rediscovery of innovative ingredients with functional properties. Finally, alternative commodities such as these are naturally gluten free sources, which is yet another advantage of their use in specific circumstances.

Food trends

In recent years and up to the present day, general concerns over the environment, sustainability and CO2 emissions, have grown considerably resulting in a heightened consumer awareness about their food's nutritional and health-giving benefits. A growing trend in this regard is that of the consumption of bread enriched with nutrient-dense ingredients which is considered a good source of functional ingredients, one that is now becoming a staple food that is largely eaten every day.

Acorn and carob flours: underexploited resources as innovative and sustainable ingredients

Despite being consumed in Roman times, the regular consumption of acorn in this form has been lost to the history books. Currently, acorns have been identified as a sustainable underexploited ingredient that can be used for human nutrition and consumption, but in reality acorns are mainly eaten by grazing animals: a substantial amount being left in fields and going to waste. Acorn is the fruit of the holm oak, Quercus ilex and Quercus rotundifolia, a surprisingly evergreen oak tree from the Quercus genus, which is one of the most important trees in the Mediterranean agroforestry ecosystem. Since holm oak is an indigenous resource in the Mediterranean area, producing fruits even under extreme adverse climatic conditions, and has always been available as an important alternative resource during years of scarcity, thanks to its ability to adapt to climatic change.

Acorn flour presents a good nutritional and functional profile, because it is rich in unsaturated fat, fibre, vitamin E, chlorophylls, carotenoids, total phenolics and rich in antioxidants, an ingredient with the potential to improve both gluten-containing and gluten-free bread's nutritional characteristics. In relation to fatty acids, acorn has about 60% oleic acid and about 16% linoleic acid, which is of benefit, since fat develops an important role in food texture, although being unsaturated.

Carob flour from Ceratonia siliqua L. also represents an underexploited fruit, that is enjoying a rapid recovery in fortunes. This tree is native to the Mediterranean coastal regions and southwest Asia. Its main use is currently for locust bean extraction, but in the previous century it was also exploited as a cacao substitute owing to its flavour and sweet taste. Carobs are low in proteins and fat, but rich in sugars and minerals as well as dietary fibre and phenolic compounds, specifically pinitol, useful for its antidiabetic properties. At a scientific level, numerous preventive and therapeutic applications have been identified including antitussive, antidiarrhoeal, antibacterial, diuretic, antiulcer, anti-inflammatory and antidiabetic as well as the treatment of gastrointestinal disorders such as gastroesophageal reflux, irritable bowel, diarrhoea and ulcerative colitis. Presumably, these characteristics are responsible for the increasing presence of either carob flour or locust bean gum, in the composition of baby foods.

Acorn and carob flour in bakery applications

With bakery innovators now searching for alternative flour sources, it will come as no surprise that acorn and carob flours have excellent potential. In fact, many bakeries in Portugal and Spain are already developing bread formulations containing these flours or a blend of both, replacing in part, the cereal flour content and they are getting very good results. The quantities of the alternative flours being used in wheat and rye formulations could vary from 8% to 20%, depending on the other mixed flours such as rye, wheat, spelt, etc., in the recipes and of course, the type of bread being baked.

An important point to note is that acorn flour used on its own introduces a bitter taste but thankfully is counterbalanced by the cocoa and sweet flavour of carob flour, producing a balanced bread presenting technological and nutritional characteristics. A further benefit to their use is that both flours are rich in unsaturated fatty acids and fibre, providing a particular texture to the bread, creating potential nutritional benefits as well. Consumers appreciate the inclusion of these flours blended with rye and/or wheat, leading to bread with a dark colour and exquisite and innovative flavour. Even the production of sourdough for bakery applications can provide opportunities for carob flour, considering its high sugar content. Likewise, the cacao taste of the carob flour is very much suited to making bakery sweets, pastries and cookies.

In conclusion, these flours can be considered as 'go to' ingredients when looking for innovative flavour and appearance in bakery items such as bread, but they can also be useful when there is a need to substitute wheat flour in non-wheat producing countries.

Acorn and carob flours in gluten-free bread

Another important bakery application for alternative flours is the production of gluten free breads. Acorn and carob flour both have a significant impact on the rheology of the dough or batter and consequently in gluten-free bread. However, these positive effects have been shown to be limited by a particular threshold which needs to be observed to obtain optimal results for the bread product being made and is determined by the correct ratio of the flours used in the formulation.

Typical ratios of carob flour to use when making gluten free breads are: replacing 15% rice flour for carob flour which allows for a bread with darker colour, better crumb structure, less hardness and slower firming time during storage. Furthermore, by applying jet-milling and further fractionation, a range of different carob flours with varying particle size distribution and chemical composition can be included. Fractionated carob flours have led to gluten free breads with a different appearance but also with a greater potential for reducing their glycemic index.

Acorn flour and debittered acorn flour have also been recognised as being suitable for making gluten free breads when used in combination with rice and corn flours. Up to 25% acorn flour could be added to a gluten-free bread recipe, improving the sensory experience when compared to rice-based breads; although its addition does decrease bread volume and increase crumb hardness, though this can be countered by adding the appropriate amount of water during breadmaking. Likewise, acorn flour significantly improves the total phenolic content of bread. The inclusion of up to 35% acorn flour has been incorporated into gluten free blends, whilst observing the acidification of the dough. This ratio can create breads with darker crumbs and with a significant increase in bioactive compounds and antioxidant properties, however, in light of rheological properties and bread features, a maximum of 23% of the dough's formulation is recommended.

Improving on the many positive attributes of sourdough, the use of acorn flour has been shown to add to that effect. Sourdough facilitates the technological characteristics of acorn flour when used to make gluten-free bread, increasing the amount of acorn flour that can be included in gluten-free recipes. This, in turn, leads to an increase in protein, unsaturated fatty acids, minerals and polyphenol content. Gluten-free bread formulations with acorn and flour/starch blends, such as: corn and potato starch, rice and corn flour or buckwheat, rice flour and potato starch offer very promising alternatives. In particular, as mentioned before, acorn flour has also been tested in combination with sourdough, showing a positive synergetic effect.

In short, acorn and carob flours show good nutritional and functional properties, demonstrating the importance of rediscovering their use as ingredients in our diets which is not only particularly relevant to the baking of gluten-free bread, but also, due to their unique characteristics, they present great potential for their inclusion in other bakery products, or different starch-based foodstuffs. Various European research teams have conducted excellent research on this subject for extending the use of such flours in bakery applications, for both 'with gluten' or gluten free breads. It only remains for this newly acquired knowledge to be integrated into innovative and dynamic, large-scale bakery businesses.

First published in BE Autumn 22