Capturing the potential value of frost damaged lentil seeds as a flour additive in baked products

Take home messages

• Damaged lentils retain high concentrations of protein and fibre.
• Dietary fibres can act as prebiotics which enhance digestive function.
• Flour produced from frost damaged lentils can be successfully incorporated into wheat-based food products adding value to the crop and providing many benefits as a novel food alternative for consumers.

Background

Lentil seeds are generally traded based on optimal quality traits relating to seed size, shape, colour and minimal defective seeds (McDonald, Panozzo, Salisbury, & Ford, 2016). Seed characteristics and yield are strongly influenced by environmental conditions such as heat stress (Delahunty, Nuttall, Nicolas, & Brand, 2015) and frost damage (Nuttall et al. 2018). However, such visual attributes which currently define price do not account for the proximal composition of the seed. In Australia, domestic pulse consumption is low compared to countries that have pulses as part of their culinary diets (Romagnolo & Selmin, 2017). The investigation into the use of pulse flour in composite specialty foods, including pasta products, breakfast cereals and snack foods, is gaining popularity in western countries (Dziki, Różyło, Gawlik-Dziki, & Świeca, 2014; Sparvoli et al. 2016; Tosh & Yada, 2010). It is also linked to improved functionality through micro and macro nutrient fortification (Rochfort & Panozzo, 2007; Takruri & Issa, 2013). To date, the utilisation of pulse flour infused products targets a niche market (Tiwari, Gowen, & McKenna, 2011).There are opportunities, however, for visually defective pulse seeds, but with acceptable composition, such as frost damaged lentils, to be used as a food additive, rather than being discarded for animal feed (Portman et al. 2018).

Method

Lentil seeds downgraded due to severe frost damage were obtained from AGT Foods, Horsham, Victoria. The seeds were air aspirated (KimSeed, Western Australia) to remove foreign matter and ground to flour using a cyclone mill fitted with a 0.5mm screen (Laboratory Mill 120; Perten Instruments, Huddinge, Sweden). Lentil flour was combined with commercially available soft wheat flour in ratios of 100% wheat, 75%-25% wheat-lentil, 50%-50% wheat-lentil, and 100% lentil. Wheat-lentil composite biscuits were baked in accordance with the method for baking quality cookie flour AACC 10-50.05 (AACC, 2000). The total % protein of the resulting composite biscuits was determined by the Dumas combustion method AACC 46-30.01 (AACC, 2000) using a Leco TruMac analyser (Leco Corp, MI, USA). The non-digestible fibre of composite wheat-lentil biscuits was determined by the neutral detergent fibre method (NDF)-ANKOM (ANKOM Technology, NY, USA). The colour of biscuits was measured using the Commission International de l’Eclairage tristimulus colour parameters (CIE) L*a*b* with a Chroma Meter CR-410 (Minolta Co., Osaka, Japan). The hardness of the biscuits was determined according to the American Institute of Baking (AIB) method for cookie hardness (Procedure, 2011) using a TA-XT2 Texture Analyzer (Stable Micro Systems, Surrey, UK).

Statistical analysis

All data were subjected to analysis of variance (ANOVA) with GenStat statistical analysis software 17th edition (VSN International, Hemel Hempstead, UK). Means were analysed for Fisher’s Least Significant Difference (LSD) with a significance level of α = 0.05. Results are expressed as mean values ± standard deviation. All analyses were conducted in triplicate.

Results and discussion

Effects of lentil flour on proximal protein and fibre composition

The proximal analyses for biscuits produced from varying composites of wheat and lentil flour are presented in Figure 1a. As was expected, the addition of lentil flour resulted in a significant increase of % protein in each composite sample (P< 0.05).

Figure 1a. Comparison of % protein and Figure 1b % fibreof lentil composite biscuits (WL). Letters that are the same are not significantly different (P<0.05).

It was determined that the average total protein concentration of frost damaged lentil was 27.6% ± 0.5, which was similar to a non-frosted Northfield lentil which had an average protein concentration of 27.5 % ± 0.1. The proximal analysis of biscuits produced with composite flour showed that insoluble fibre (Figure 1b) also significantly increased with increasing concentration of lentils (P< 0.05). Both protein and fibre concentration and quality are important considerations within novel food development (Asif, Rooney, Ali, & Riaz, 2013). The inclusion of lentil flour not only enhances the amount of protein present, but the quality of protein is substantially better having a more diverse amino acid profile (Boye, Zare, & Pletch, 2010; Portman et al. 2018). Furthermore, the increase of fibre shown in this experiment may have a functional benefit. Specifically, these fibres facilitate greater movement of material through the digestive system (Tosh & Yada, 2010). Insoluble fibres, including cellulose, hemicellulose and lignin, are fermented in the large intestine, resulting in the formation of short chain fatty acids (SCFAs). It has been proposed that SCFAs limit the effects of chronic inflammation, atherosclerosis and metabolic disorders (Ohira, Tsutsui, & Fujioka, 2017).

Effect of lentil flour on the sensory evaluation of biscuits

The colour and hardness of the biscuits were measured to assess the effect of lentil flour. These are shown in Figure 2. There was significantly visible darkening of the biscuit with the addition of 25% and 50% lentil (P< 0.05), but there were no significant differences for darkness when comparing the higher concentrations of 50% and 100% composite blends. This darkening effect is most likely caused by an increase in oligosaccharide sugars found in lentils, which participate in the Maillard reaction (Martins, Jongen, & Van Boekel, 2000; Tamanna & Mahmood, 2015; Žilić et al. 2013). Thus, the browning effect could potentially be reduced by varying the cooking time and temperature.

Figure 2. Examples of wheat-lentil biscuits made using lentil flour milled from frost damaged lentil seeds.

Increasing the concentration of lentil flour also affected the firmness of the biscuits (Figure 3). Concentrations of 25% and 50% significantly reduced the firmness of the biscuit compared to the 100% wheat biscuit (P< 0.05), and this is probably due to a dilution effect that lentil flour has on wheat gluten (Portman et al. 2018). However, increased concentrations of lentil flour result in increased firmness which is most likely a result of a higher fibre content leading to a higher water absorption capacity. The hardness of the wheat-lentil composite biscuits was also compared with two similar style store bought biscuits (Biscuit 1 and Biscuit 2). Wheat-lentil composite biscuits were softer at the lower concentrations and comparable in hardness at the 100% level.

Figure 3. Biscuit hardness. Biscuit 1 and Biscuit 2 are commercial brands available in store. Letters that are the same are not significantly different (P<0.05).

Conclusion

Frost damaged lentil seeds had a concentration of both protein and fibre comparable to non-frosted Northfield lentil seed. Wheat-lentil composite biscuits had superior levels of both protein and fibre when compared to wheat biscuits. Visually, wheat-lentil composite biscuits retained an acceptable quality in both colour and firmness when compared to similar commercially available biscuits. There are many benefits that can be gained from creating novel food products through the incorporation of pulse flours, such as the frost damaged lentil flour used in this experiment.

References

AACC, I. (2000). Approved Methods of the AACC. Association of Cereal Chemists, St. Paul.

Asif, M., Rooney, L. W., Ali, R., & Riaz, M. N. (2013). Application and opportunities of pulses in food

system: a review. Critical reviews in Food Science and Nutrition, 53(11), 1168-1179.

Boye, J., Zare, F., & Pletch, A. (2010). Pulse proteins: Processing, characterization, functional

properties and applications in food and feed. Food Research International, 43(2), 414-431.

Delahunty, A., Nuttall, J., Nicolas, M., & Brand, J. (2015). Genotypic heat tolerance in lentil. Paper

presented at the Proceedings of the 17th ASA Conference.

Dziki, D., Różyło, R., Gawlik-Dziki, U., & Świeca, M. (2014). Current trends in the enhancement of

antioxidant activity of wheat bread by the addition of plant materials rich in phenolic compounds.

Trends in Food Science & Technology, 40(1), 48-61.

Martins, S. I., Jongen, W. M., & Van Boekel, M. A. (2000). A review of Maillard reaction in food and

implications to kinetic modelling. Trends in Food Science & Technology, 11(9), 364-373.

McDonald, L. S., Panozzo, J. F., Salisbury, P. A., & Ford, R. (2016). Discriminant analysis of defective

and non-defective field pea (Pisum sativum L.) into broad market grades based on digital image

features. PloS one, 11(5), e0155523.

Nuttall, J. G., Perry, E. M., Delahunty, A. J., O'Leary, G. J., Barlow, K. M., & Wallace, A. J. (2018). Frost

response in wheat and early detection using proximal sensors. Journal of Agronomy and Crop

Science.

Ohira, H., Tsutsui, W., & Fujioka, Y. (2017). Are short chain fatty acids in gut microbiota defensive

players for inflammation and atherosclerosis? Journal of Atherosclerosis and Thrombosis, 24(7),

660-672.

Portman, D., Blanchard, C., Maharjan, P., McDonald, L. S., Mawson, J., Naiker, M., & Panozzo, J. F.

(2018). Blending studies using wheat and lentil cotyledon flour—Effects on rheology and bread

quality. Cereal Chemistry, 95(6), 849-860.

Procedure, A. S. (2011). Texture analysis procedures: Research Department, Kansas City: American

Institute of Baking.

Rochfort, S., & Panozzo, J. (2007). Phytochemicals for health, the role of pulses. Journal of

Agricultural and Food Chemistry, 55(20), 7981-7994.

Romagnolo, D. F., & Selmin, O. I. (2017). Mediterranean diet and prevention of chronic diseases.

Nutrition Today, 52(5), 208.

Sparvoli, F., Laureati, M., Pilu, R., Pagliarini, E., Toschi, I., Giuberti, G., . . . Bollini, R. (2016).

Exploitation of common bean flours with low antinutrient content for making nutritionally enhanced

biscuits. Frontiers in Plant Science, 7, 928.

Takruri, H. R., & Issa, A. Y. (2013). Role of lentils (Lens culinaris L.) in human health and nutrition: a

review. Mediterranean Journal of Nutrition and Metabolism, 6(1), 3-16.

Tamanna, N., & Mahmood, N. (2015). Food processing and maillard reaction products: effect on

human health and nutrition. International Journal of Food Science, 2015.

Tiwari, B. K., Gowen, A., & McKenna, B. (2011). Pulse foods: processing, quality and nutraceutical

applications: Academic Press.

Tosh, S. M., & Yada, S. (2010). Dietary fibres in pulse seeds and fractions: Characterization,

functional attributes, and applications. Food Research International, 43(2), 450-460.

Žilić, S., Mogol, B. A., Akıllıoğlu, G., Serpen, A., Babić, M., & Gökmen, V. (2013). Effects of infrared

heating on phenolic compounds and Maillard reaction products in maize flour. Journal of Cereal

Science, 58(1), 1-7.

Acknowledgements

The authors would like to thank Agriculture Victoria, Horsham; The Functional Grains Centre, Charles Sturt University and AGT Foods Australia.

Contact details

Drew Portman
Agriculture Victoria, 110 Natimuk Road, Horsham, Vic 3401
(03) 43443131
aportman@csu.edu.au