Elsevier

Journal of Functional Foods

Volume 29, February 2017, Pages 93-103
Journal of Functional Foods

Sorghum and roasted coffee blends as a novel extruded product: Bioactive compounds and antioxidant capacity

https://doi.org/10.1016/j.jff.2016.12.012Get rights and content

Highlights

  • Whole sorghum flour and roasted coffee were processed by thermoplastic extrusion.

  • Coffee addition increased bioactives: fiber, phenolics and minerals in extrudates.

  • Gluten free and fiber rich ingredients were used to produce new functional product.

  • The sorghum extrudate with 20% coffee would be an interesting source of bioactives.

Abstract

Addition of roasted coffee powder (CP) in whole grain sorghum flours of two genotypes were extruded in two water content conditions and the variations of total phenolic compounds (TP), phenolic acids and antioxidant capacity (AC) were investigated as well as the functional properties. Increasing CP and moisture lead to a reduction of expansion, paste viscosity and water and solubility indexes. TP was reduced in sorghum depending on the genotype (10 and 40%) after extrusion whereas in mixtures with CP, TP increased. The extrusion promoted a decrease of AC, but mixtures with CP still had higher AC than those with only sorghum. The present study indicates that it is possible to produce sorghum extrudates and CP with good antioxidant properties and phenolic compounds.

Introduction

Extrusion cooking is an industrial cooking process that combines high pressure, heat and mechanical force in a short period of time, causing physical and chemical changes. Besides, extrusion has been used to create new products using blends and ingredients that follow a continued growth of the food market (Tovar-Jiménez et al., 2015). It has been reported that the extrusion cooking could influence the amount of bioactive compounds like phenolics, carotenoids, among others, which depends on the food matrix. In recent years, a considerable number of works has been investigating the effect of extrusion of cereals added of varied sources of vegetables, such as fruits and pulses (Morales et al., 2015), mainly containing bioactive compounds.

Coffee is the main source of caffeine, but has many other compounds, such us phenolic compounds, minerals (Mg, K), antioxidant capacity and dietary fiber and can be considered as a functional food (Esquivel & Jiménez, 2012). Coffee, limited as a filtered infusion or instant powder, is the most frequently consumed product worldwide, but with the rapid changes of consumers market, its use as an ingredient in blends with whole cereal grain would be considered in the development of new products rich in bioactive compounds.

Sorghum is the fifth consumed cereal in the world, mainly used for manufacturing feed products, however more recent attention has be given to its potential as a food due to the nutritional aspects (gluten free, high content of bioactives) and agronomical qualities (drought and heat tolerant crop among others) (Yousif, Nhepera, & Johnson, 2012). As a whole grain, this cereal has the highest level of antioxidants when compared with other cereals such us rice, corn and wheat (Ragaee, Abdel-Aal, & Noaman, 2006). Use of whole grain sorghum flour in formulations, for example, in bakery and expanded extrudates (Vargas-Solórzano, Carvalho, Takeiti, Ascheri, & Queiroz, 2014) has contributed to increase the intake of phenolic compounds, thus it may provide protective effects against chronicle diseases and yet, sorghum is a gluten free cereal (N'Dri et al., 2013).

Considering the available literature, there is no study on the effect of extrusion on some bioactive compounds in blends of roasted coffee powder and whole grain sorghum. Thus, the aim of this work was to study the effect of extrusion on the physicochemical, bioactive compounds and antioxidant capacity changes occurring on the extrusion of whole grain sorghum flours of two genotypes (with and without tannin) added of roasted coffee powder.

Section snippets

Material

Commercial roasted coffee powder (Coffea arabica L.) was obtained from the local market (Rio de Janeiro, Brazil). Two sorghum genotypes (Sorghum bicolor L. Moench) with same light brown pericarp color, 9929026 and 2012038, with and without tannins, respectively were provided by Embrapa Maize and Sorghum (Sete Lagoas, MG, Brazil). The grains were cleaned and stored for further evaluation.

Chemical composition

The moisture content was determined according to AOAC (2010), method 925.09. Fat content was calculated

Chemical composition

The chemical composition of CP and SGs are presented in Table 1. CP showed higher amount (p < 0.05) of ash, protein, fat and dietary fiber than both SGs. The chemical composition of SGs were comparable to the results reported by Vargas-Solórzano et al. (2014). For fiber content, they found values between 8.52 and 12.86 g.100 g−1 for different genotypes while Khan, Yousif, Johnson, and Gamlath (2013) found 9.00 g.100 g−1 of dietary fiber for red sorghum, whereas in this work the dietary fiber was

Conclusion

Addition of coffee powder and water decreased the radial, crispness and volumetric expansion indices, as well the paste viscosity readings particularly cold viscosity and increased bulk density of the extrudates. As CP presented high content of dietary fiber (∼50%), the extruded mixtures with CP showed an increase of fiber content.

The results show that there is a relationship between total phenolic content, phenolic acids and antioxidant capacity. Roasted coffee powder exhibited the highest

Acknowledgements

The authors would like to thank the scholarship granted by CNPq (Brazil) to José L. R. Ascheri and the financial support provided by CNPq and FAPERJ (Brazil). They also thank the donation of sorghum genotypes by Embrapa Maize and Sorghum (Sete Lagoas, Brazil).

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