The Influence of Soaking and Sprouting on the Physicochemical Characteristics of Tigernut Tubers (Cyperus esculentus L.)

Abstract

The influence of soaking and germination on the physicochemical characteristics of tigernut tubers (Cyperus esculentus L.) are investigated. Tubers (Ø > 1 cm) were soaked in an ascorbic acid solution (0.1%) for 48 h at 40 °C before undergoing germination for 6 days. The textural profile, the capacity and germination energy and the biochemical composition of these tubers were determined. The germination energy varied from 76.18 to 79.48% for the quantities of solution of 24 and 48 mL, respectively. The textural profile of the tubers varied depending on the type of treatment. Germination resulted in a considerable reduction in amylose content from 14.15% for the native tigernut tuber to 9.98% for the sprouted one. This treatment also increased the protein, ascorbic acid and ash contents, which ranged from 7.54 to 8.82 g/100 g DM, 250 to 275.39 mg/100 g DM and 2.60 to 3.84 g/100 g DM, respectively. The starch content of the tubers following germination remained high, which could come up against the pasteurization of the milk from these tubers.

Effects of sprouting duration on the nutrient, functional, and phytochemical properties of tiger nut flour, and the sensory properties of bread made thereof

“…The soluble sugar content of the freshly harvested, native TNs was 11.94 ± 0.31 • Bx, which increased to 34.38 ± 2.39 • Bx (Figure 2) after the drying period and milling process, confirming that the temperature and exposure period contribute to the accumulation of sugar in TNs (Kizzie-Hayford, Dabie, et al, 2021). The sproutingrelated decrease of the sugar content of TN in this study is contradictory to the increase shown by Djomdi et al (2022). This disparity can be partly attributed to the state of the TN prior to sprouting: On the one hand, freshly harvested TN shows a low sugar content (Kizzie-Hayford, Dabie , et al, 2021), and the amylase activity is reported to be minimal between 30 and 40 • C (Avwioroko et al, 2019), being comparable to the sprouting temperature.…”

“…Shoots of sprouted TNs (Figure 1) were visually detectable after 3 days of incubation. The fraction of sprouted tubers after 3 days was 78% ± 4.5%, which is in the upper level of the range (0%-75%) reported in literature (Djomdi et al, 2022). TNs are sometimes treated with hydrogen peroxide, ascorbic acid (Djomdi et al, 2022), or sodium hypochlorite (Okoye & Eni, 2018) to disinfect and prevent fungal growth during sprouting, and both the concentration and the type of disinfectant may affect sprouting efficiency (Tornuk et al, 2011).…”

“…However, Özcan et al (2021) showed a decrease in the protein and ash contents after sprouting TNs for 2 days. Sprouting was also reported to increase the lipid content of TN (Adebayo & Arinola, 2017;Özcan et al, 2021), which was contrary to the report by Okoye and Eni (2018) and Djomdi et al (2022). Moreover, Adebayo and Arinola (2017) showed that the sprouting of TNs resulted in an increase of the content of fiber, which was ascribed to the synthesis of cellulosic materials.…”

“…Moreover, Adebayo and Arinola (2017) showed that the sprouting of TNs resulted in an increase of the content of fiber, which was ascribed to the synthesis of cellulosic materials. On the contrary, Djomdi et al (2022) reported insignificant effects of sprouting on fiber, whereas Okoye and Eni (2018) reported a decrease in the fiber content.…”

“…A few authors performed experiments with sprouting TN, aiming at improving the nutritional and phytochemical quality. Some reports showed that the sprouting of TNs for 2 days (Adebayo & Arinola, 2017), 4 days (Okoye & Eni, 2018), or 6 days (Djomdi et al, 2022) resulted in an increase of the protein and ash content, which was ascribed to the synthesis of enzymes and metalloproteins. However, Özcan et al (2021) showed a decrease in the protein and ash contents after sprouting TNs for 2 days.…”