Phenotyping of yam genotypes for a high quality of boiled and pounded products

Phenotyping of yam genotypes for a high quality of boiled and pounded products Abomey-Calavi, Benin, October 2025 Laurenda HONFOZO, UAC-FSA, Cotonou, Benin Penelope PEDE, UAC-FSA, Cotonou, Benin Francis HOTEGNI, UAC-FSA, Cotonou, Benin Laurent ADINSI, UAC-FSA, Cotonou, Benin Noël AKISSOE, UAC-FSA, Cotonou, Benin RTBfoodomics Period 1 Institute Report Page 2 of 20 This report has been written in the framework of the RTBfoodomics project (under CIRAD coordination), as a continuation of work initiated under the RTBfoods and RTB Breeding projects. To be cited as: Laurenda HONFOZO, Penelope PEDE, Francis HOTEGNI, Laurent ADINSI, Noël AKISSOE (2025). Phenotyping of yam genotypes for a high quality of boiled and pounded products. Abomey-Calavi, Benin: RTBfoodomics, Scientific Report, 20 p. https://doi.org/10.5281/zenodo.17611132 Ethics: The activities, which led to the production of this document, were assessed and approved by the CIRAD Ethics Committee (H2020 ethics self-assessment procedure). When relevant, samples were prepared according to good hygiene and manufacturing practices. When external participants were involved in an activity, they were priorly informed about the objective of the activity and explained that their participation was entirely voluntary, that they could stop the interview at any point and that their responses would be anonymous and securely stored by the research team for research purposes. Acknowledgments: This work was supported by the RTBfoodomics, through a grant from the Bill & Melinda Gates Foundation (BMGF) to the French Agricultural Research Centre for International Development (CIRAD), Montpellier, France, incorporated in the grant agreement INV-054662_2024 between CIRAD and BMGF. Image cover page © CIRAD. RTBfoodomics Period 1 Institute Report Page 3 of 20 This document has been reviewed by Noel AKISSOE Oluwatoyin AYETIGBO 09/2025 09/2025 Final validation by Dominique DUFOUR 10/2025 RTBfoodomics Period 1 Institute Report Page 4 of 20 Table of Contents Table of Figures ........................................................................................................................................5 Abstract ....................................................................................................................................................6 1 Context .............................................................................................................................................7 2 Methodology ....................................................................................................................................7 2.1 Plant materials sampling ......................................................................................................... 7 2.2 Boiled yam preparation ........................................................................................................... 7 2.3 Pounded yam preparation ...................................................................................................... 7 3 Results ..............................................................................................................................................8 3.1 Varietal and storage effects on textural parameters of boiled yam ....................................... 8 3.2 Boiled yam crumbliness prediction and positioning to thresholds ....................................... 12 3.2.1 Using LDPeak/Apeak parameter ................................................................................... 12 3.2.2 Using maximum force Fpeak parameter ....................................................................... 12 3.3 Effect of storage duration on pounded yam extensibility ..................................................... 16 3.4 Effect of storage on sensory descriptors of pounded yam at harvest time to fourth month of storage ............................................................................................................................................... 16 4 Conclusion ..................................................................................................................................... 20 References ............................................................................................................................................. 20 RTBfoodomics Period 1 Institute Report Page 5 of 20 TABLE OF FIGURES Table 1: Fpeak parameter of boiled yam as affected by varietal and storage effects ............................ 9 Table 2: LDpeak/Apeak parameter of boiled yam as affected by varietal and storage effects ............ 10 Table 3: Boiled yam crumbliness prediction based on LDPeak/Apeak parameter ............................... 13 Table 4: Boiled yam crumbliness prediction based on Fpeak parameter ............................................. 14 Table 5: Pounded yam extensibility (mm) as affected by storage duration ......................................... 17 RTBfoodomics Period 1 Institute Report Page 6 of 20 ABSTRACT Making good yam available all the year for processing yam derivatives is one of breeding challenges. Boiled and pounded yams are popular and widely consumed dishes in West Africa, but they depend on yam genotypes. In addition, storage of yam tubers affects quality of these derived products. The study aimed at evaluating the texture behavior of boiled and pounded yam during storage for six months. Yam genotypes (17) including seven landraces and ten hybrids were selected for base line test and storage. Instrumental analyses of texture were performed on both products using uniaxial texture analyser. Some yam genotypes gave high quality products only just after harvest while other were less good at harvest time, then improved with storage. Some genotypes exhibited a pic quality behaviour, with low quality at harvest time, improved for few months and then became low again. Other genotypes had low quality from the beginning to the end of storage, considering optimal threshold. Key Words: hybrids, pounded yam, boiled yam storage, extensibility, crumbliness, screening RTBfoodomics Period 1 Institute Report Page 7 of 20 1 CONTEXT Boiled yam and Pounded yam are widely consumed dish in many countries of West Africa (Otegbayo et al, 2023). Pounded yam major trait is its stretchability while crumbliness plays a determining role in the acceptability of boiled yam. The high quality of both products depends on the variety/genotype used for preparation, all other things being equal. Generally, only some varieties belonging to D. cayenensis-rotundata species are appropriate for making both products and in a lesser extent few D. alata varieties (Ebah-Djedji et al, 2023). A high-quality boiled or pounded yam is not often available all the year round due to the scarcity of appropriate yam varieties for making pounded yam. It is therefore necessary to store yam tubers for a relatively long period to ensure the availability of both products at any period of the year. Moreover, previous studies showed that during storage, the quality of derived products changes significantly. Specifically, for pounded yam, stretchability can be affected by storage duration of raw yam (Hounhouigan et al, 2003; Akissoe et al, 2009, Ebah-Djedji et al, 2023). Stretchability and crumbliness thresholds have been determined for boiled and pounded yam (Adinsi et al, 2024). These thresholds can then be used to discriminate varieties/genotypes. Since some varieties can be good or relatively good for boiling and pounding at beginning and become low or better after storage, it is important to consider storage while screening varieties. The study aimed at appreciating the effect post-harvest storage on boiled and pounded yam. 2 METHODOLOGY 2.1 Plant materials sampling Plant materials comprised 16 yam genotypes obtained from Biorave center fields located at Bassila, Dassa-Zoumè, Djougou and Massi. These genotypes were composed of landraces (Assinaga, Assoura, Bakaro, Kpèguèlèhoun, Makpa Tolaha and Odo) and hybrids (TDr1000344 (Idoro), TDrA5-2003, TDr8902665, TDr1443002, TDa1510119, TDa1510043, TDa1515030, TDa1508044, TDa1520002 and TDa1520008). Kpèguèlèhoun belonging to landraces category was from D. alata specie. They were harvested in December 2024 and stored for 6 months. All genotypes were stored at room in a wellventilated attic at the BIORAVE center in Massi. Each month, tubers of each genotype were collected and processed in pounded yam which were characterised from 15 days after harvest to 6 months of storage. 2.2 Boiled yam preparation Two (2) to ten (10) yam tubers per genotype, were peeled after removing of 1/10 of from end part (distal and proximal). Per tuber, a punch was used to take cubic samples having 2.5 cm sides. The cubic samples were divided into batches: one for steam-cooking while the second from frieze drying after grating. This experimental design was performed for each tuber. Subsequently the samples for steaming or freeze drying were mixed by batch. In total, around 40 cubic samples were collected and steam-cooked during 38 min, while 200 g of grated fresh sample was considered. After steam cooking, 10-12 cubic samples were used for texture analysis while the remaining was stored at -80 °C for freeze drying. 2.3 Pounded yam preparation RTBfoodomics Period 1 Institute Report Page 8 of 20 Pounded yam was prepared according to standard procedure developed by Adinsi et al. (2024). Two (2) to six (06) yam tubers per genotype depending on their size were considered. Each tuber was divided in half lengthwise to obtain two pairs (T1a and T1b). For each cooking batch, the combination from at least two tubers (T1a and T2a) was used. The second combination (T1b and T2b) represented the replicate for the same genotype. Then, each half of the tubers from a cooking batch were cut into small cubes. Subsequently the samples for pounding and freeze drying were collected. 450 g of the mixture was steamed in a pounder with 250 mL of water for approximately 23 minutes, then pounded for 4 minutes. After pounding, approximately 350 g of the pounded yam was used for sensory analysis, and approximately 150 g for texture analysis (extensibility test). 3 RESULTS 3.1 Varietal and storage effects on textural parameters of boiled yam The maximum force (Fpeak) (Table 1) and LDpeak/Apeak (Table 2) were significantively affected by varietal effect (p-value < 0.0001) (Table 1) and storage duration except for Odo and TDa1520002 for Fpeak and LDpeak/Apeak respectively. D. alata hybrids registered the highest values of LDpeak/Apeak compared to D. rotundata hybrids and landraces. Four groups of Fpeak behaviour were observed: increase from t0+15 days until the end of storage duration, decrease from t0+15 days to the first months and increased until the end of storage duration, no modification from t0+15 days to the first months and increased until the end of storage duration and sawtooth trend. As far as LDpeak/Apeak is concerned, the similar behaviours, however the decrease were observed instead the increase in Fpeak. The highest Fpeak values and LDpeak/Apeak were registered generally at the end and beging of storage. RTBfoodomics Period 1 Institute Report Page 9 of 20 Table 1: Fpeak parameter of boiled yam as affected by varietal and storage effects Genotypes T0+15 days 1 month 2 months 3 months 4 months 5 months 6 months Assinaga 5.4,3 nd 6.5,3 8.5,2 9.1,12 10.2,1 nd Assoura 7.9,12 nd 8.5,12 7.2,2 7.6,12 8.7,1 nd Bakaro 5.6,4 nd 6.4,34 7.4,23 7.7,2 10.0,1 nd Kpèguèlèhoun 4.5,3 5.3,23 6.5,12 7.4,1 7.8,1 7.9,1 nd Makpa Tolaha 6.3,2 nd 5.9,2 6.9,2 8.9,1 8.3,1 nd Odo 6.1,1 6.2,1 nd nd nd nd nd TDa1508044 3.8,12 2.5,2 4.2,12 4.3,12 4.7,1 5.4,1 4.7,1 TDa1510043 3.0,2 4.6,2 3.1,2 5.6,1 4.0,12 4.2,12 3.7,2 TDa1510119 2.8,2 5.3,1 5.2,1 3.4,12 5.4,1 2.9,2 2.4,2 TDa1515030 3.9,3 4.2,23 5.2,123 5.9,1 5.9,12 3.8,3 3.8,3 TDa1520002 3.0,2 2.8,2 4.8,12 3.4,2 3.2,2 2.8,2 5.9,1 TDa1520008 3.6,2 4.2,12 4.1,12 5.1,12 3.7,12 5.8,1 3.8,12 TDr1000344 (Idoro) 6.5,2 nd 6.7,2 5.5,3 8.7,1 8.2,1 nd TDr1443002 5.0,3 6.5,2 5.1,23 6.3,23 6.3,23 8.9,1 nd TDr8902665 6.1,2 nd 5.5,2 6.5,2 6.2,2 8.0,1 nd TDrA5-2003 5.1,3 5.1,3 6.0,23 5.6,3 7.0,12 7.6,1 nd RTBfoodomics Period 1 Institute Report Page 16 of 20 3.3 Effect of storage duration on pounded yam extensibility Extensibility was affected by genotype and storage period. For the most of genotypes, the extensibility showed sawtooth trends; it increased at the first period, then decreased and increased once again (Assinaga, Bakaro, Kpèguèlèhoun etc). Comapred to initial period, D. alata hybrids highlighted an increase of their extensibility at the sixth month than D. rotundata ones. However, they recorded the lowest extensibility throughout the storage duration with some of them (TDa1508044, TDa1520008 and TDa1515030) reaching an acceptable extensibility at five and six months. The optimal threshold of extensibility is represented by a value above 3.38 mm (green colour), the acceptable threshold is indicated by an extensibility > 2.77 and < 3.38 mm (yellow colour) while a low threshold stands for an extensibility < 2.77 mm (red colour) (Table 5). Only the genotypes belonging to D. rotundata species registered the optimal threshold of extensibility. 3.4 Effect of storage on sensory descriptors of pounded yam at harvest time to fourth month of storage The sensory mapping of pounded yam from harvest time, revealed that F1 and F2 axis gathered 97.72% of information on pounded yam descriptors (Figure 1). Moreover, as far as sensory descriptors of extensibility, softness and sweetness are concerned, two groups of genotypes were distinguished. The first one comprised D. rotundata genotypes which were associated to the descriptors extensible and sweet while the second group was made of D. alata genotypes, associated to the softness of pounded yam (Figure 1). At fourth month of storage, the sensory mapping performed showed that all D. rotundata genotypes were in the same dial and were associated to the three descriptors Extensible, Soft and Sweet. All D. alata genotypes involved in this test were associated to none descriptor with F1 and F2 axis gathering 99.3% of information on pounded yam (Figure 2). RTBfoodomics Period 1 Institute Report Page 17 of 20 Table 5: Pounded yam extensibility (mm) as affected by storage duration Genotypes t0+15 days 1 month 2 months 3 months 4 months 5 months 6 months Assinaga 3.9bc 4.4ab 3.1d 3.5cd 3.7cd 4.7a _ Assoura 5.8a 3.7d 5.5ab 4.6c 3.8d 5.2b _ Bakaro 4.6ab 5.0a 4.5ab 3.6c 2.8d 4.2bc _ Kpèguèlèhoun 2.0c 2.7b 2.3bc 2.4bc 2.4bc 3.3a _ Makpa Tolaha 3.1b 3.4b 3.4b 4.6a 2.9b 5.1a _ Odo 4.5a 4.3a _ _ _ _ _ TDa1508044 1.8c 1.4c 2.6ab 1.6c 1.8c 2.3b 2.8a TDa1510043 1.2c 1.7b 1.1c 1.3c 1.2c 2.6a 2.6a TDa1510119 1.2cd 1.1d 1.3cd 1.6bc 1.5bcd 1.7ab 2.1a TDa1515030 1.2d 1.2d 2.2b 1.7bc 1.6cd 3.0a 2.7a TDa1520002 1.0bc 0.7c 0.8bc 1.1bc 1.2b 2.4a 2.1a TDa1520008 1.0a 1.5ab 2.0bc 2.1c 1.8bc 3.1d 2.7d TDr1000344 (Idoro) 3.6b 4.0b 5.1a 3.6b 3.2b 3.8b _ TDr1443002 3.1b 4.2a 3.2b 4.3a 3.3b 3.4b _ TDr8902665 3.5b 4.2a 2.7c 3.4b 2.8c 4.7a _ TDrA5-2003 2.3c 3.6b 4.5a 2.9bc 3.4b 4.5a _ p-value < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 RTBfoodomics Period 1 Institute Report Page 18 of 20 Green color: optimal threshold Yellow color: acceptable threshold Red color: below acceptable threshold RTBfoodomics Period 1 Institute Report Page 19 of 20 Figure 1: Sensory mapping of pounded yam from genotypes at harvest time Figure 2: Sensory mapping of pounded yam from genotypes at fourth month of storage Extensible Soft Sweet Mètchassa Assinaga Assoura Bakaro kpèguèlèhoun Makpa tolaha Odo TDa1508044 TDa1510043 TDa1510119 TDa1515030 TDa1520002 TDa1520008 TDr1000344 (Idoro) TDr1443002 TDr8902665 TDrA5-2003 -2,5 -2 -1,5 -1 -0,5 0 0,5 1 1,5 2 2,5 3 -2 -1,5 -1 -0,5 00,5 11,5 22,5 3 F2 (32.86 %) F1 (64.86 %) Biplot (axes F1 & F2 : 97.72 %) Variables actives Observations actives Extensible Soft Sweet Assinag a Assoura Bakaro kpèguèlèhoun Makpa tolaha TDa1508044 TDa1510043 TDa1510119 TDa1515030 TDa1520002 TDa1520008 TDr1000344 (Idoro) TDr1443002 TDr8902665 TDrA5-2003 -2 -1,5 -1 -0,5 0 0,5 1 1,5 2 2,5 3 -2 -1 0123 F2 (10.46 %) F1 (88.84 %) Biplot (axes F1 & F2 : 99.30 %) Variables actives Observations actives RTBfoodomics Period 1 Institute Report Page 20 of 20 4 CONCLUSION Storage considerably impacted/changed the quality of boiled and pounded yam from genotypes. Different behaviours were observed, suggesting promising capability of yam genotypes studied. Some varieties like Laboko which is highly appreciated for the quality did not store for long period while other stored better with increasing, sawtooth or updown food quality. This raises the problem of the ability of some genotypes to be stored for guaranteeing the availability of the most liked yam derivatives all the year round. It is therefore an important issue, and even more so a priority for breeding programmes. REFERENCES Adinsi, L., Honfozo, L., and Akissoé, N. (2021). Sample preparation and cooking time for texture analysis of boiled yam, in Biophysical Characterisation of Quality Traits, WP2. RTBfoods Laboratory Standard Operating Procedure, Cotonou, reporting/download/report_file_id/25510. Benin, p. 15 https://mel.cgiar.org/ Adinsi, L., Djibri‐Moussa, I., Honfozo, L., Bouniol, A., Meghar, K., Alamu, E. O., ... & Akissoé, N. H. (2024a). 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