Sinking your teeth into sorghum rotis

Evaluating organoleptic qualities of varieties

Roti’s being cooked. Photo: Jana Kholova

Crop value is determined not just by grain produced per hectare but also by its nutritional content. Improving the nutrient density of staple crops can play a role in stamping out malnourishment that endangers the health and development of subsistent farming communities, especially among women and children in the semi-arid tropics.

Recently, the SACSA (System analysis for climate smart agriculture, ICRISAT) team in collaboration with the NutriPlus Knowledge Program (NPK) of AIP-ICRISAT, International Livestock Research Institute (ILRI) and WorldFish established a new research stream dedicated to investigating GxExM (Genotype X Environment X Management) interactions with sorghum grain and stover nutritional profiles. Trials so far reveal that the nutrient profiles of sorghum grains are significantly influenced by stay-green QTL (Qualitative Trait Loci) alleles as well as water, fertilizer and plant population treatments. That got us wondering if consumers would be able to taste the difference in nutrient densities in samples exposed to different crop GxExM treatments and if so, would improved nutrient composition (e.g. protein, Fe) also mean improved product acceptability?

We put this to the test by organizing a “tasting session” of sorghum roti (a flat bread common in SAT farming communities) made from our experimental grain samples. The informal session had a diverse group of 17 tasters from 6 continents evaluating the basic organoleptic qualities of four sorghum roti samples. The tasting panel was split into two groups based on the frequency of their roti consumption. The ‘Indigenous’ group of 9 were regular consumers while the ‘Foreign’ group of 8 were rare consumers.

The four sample grains were dried to 10% moisture and ground in an industrial flour mill. Sample A was a senescent variety R-16 grown under well-watered conditions (WW) and with inferior nutrient value. Sample B was the locally popular Maldandi M35-1 grown under WW and with ~20% higher protein compared to others (12.4g/100g flour). Sample D was Maldandi M35-1 grown under water stress (WS) conditions and with significantly lower protein compared to sample B (10.5% or 10.5g/100g flour). Sample C was the Ethiopian variety S35 grown under WW conditions and with ~50% higher Fe (27.4ppm) and ~30% lower lipids (2.87g/100g flour) content compared to the others.

Roti’s being tested by the panel team. Photo: Jana Kholova

While kneading and baking, we observed apparent variations between the samples. Dough from sample B and D (both Maldandi) was smooth and the rotis were easy to make. The WW sample B had better puffing quality compared to WS sample D. Flour from R-16 variety was rough, granulated and showed less puffing compared to samples B and D, while flour made from sample C (S35 variety) was the worst in terms of both kneading and baking qualities.

Rotis done, participants tasted all the four samples and evaluated them in a questionnaire, choosing their favourite sample and rating them on a scale of 1-4 (1=good; 2=fair; 3=average; 4=bad). Participants who are used to consuming rotis regularly rated samples as significantly better. Segregated data was further compared using ANOVA (CoHort Software, Monterey, CA, USA) and the main results are shown in Table 1.

Significant differences in roti taste were observed when these were combined with subji (vegetable/curry) in the indigenous group and overall despite similar trends observed for all investigated qualities in both groups. Regular roti consumers were more sensitive to differences in roti quality. For the most contrasting organoleptic quality (roti combined with subji), sample B (M35-1, WW treated, high protein) received significantly higher scores and both taster groups described it as unacceptable. Indigenous tasters generally preferred samples A and D while foreign tasters valued samples A and C.

This preliminary study indicates that our tasting panel was able to taste the differences in rotis and agree on general acceptability/non-acceptability of samples regardless of geographic origin. The panel appeared to grade the less nutritionally dense samples (A and D) as more tasty.

The big surprise was the clear difference in taste and acceptability of samples B and D, both Maldandi but while sample B was collected from crop grown in optimal conditions, sample D came from a water and fertilizer stressed crop, clearly demonstrating the huge effect the environment has on the acceptability of sorghum products. However, from this we cannot draw conclusions on whether non-acceptability of sample B was related to its high protein content.

If more nutritionally dense sorghum samples are less accepted by tasters and environmental conditions during crop growth can lead to extreme changes in product acceptability, what does this imply in terms of research focus? Any recommendation?

Table 1: Evaluation of basic organoleptic qualities of four samples of sorghum rotis:  Sample A from a senescent variety R-16, B from Maldandi M35-1, C from an Ethiopian variety S35 and D from Maldandi M35-1.

¹ Significant differences between four samples evaluated within two significantly different groups of tasters (Indigenous, Foreign) and Overall.

About the author:
Ms. Keerthi Chadalavada , Research Scholar, ICRISAT.