(231am) Characterization of Sweet Potato (Ipomoea batatas L.) Starch from Two Clones and Evaluation of Its Properties for Industrial Uses

Sweet potato (Ipomoea batatas L.) is a dicotyledonous plant belonging to the family Convolvulaceae, with approximately 50 genera and over 1000 species (Woolfe, 1992). Artificial selection of sweet potatoes varieties, as well as natural hybrids and mutations resulted in these large cultivars varieties (Zhang; C.G. and Oates, 1999). These varieties differ in composition and several of its physicochemical properties, such as starch content, gelatinization temperature, dry matter, color, viscosity, water retention and granule size.

Due to increases on demand of sweet potato products, since are widely known its functional and nutraceutical properties owing to antioxidant activities, as a consequence of outstanding content of anthocyaninscarotenoids, flavonoids and other phenolic compounds, previously reported (Teow, et al., 2007) and increase of diseases associated to starch from cereal products ingestion is mandatory to determine the composition and physicochemical properties and thus its possible industrial uses.

In order to characterize sweet potato starch from two varieties, known as Tainung and 199062-1 clones, physicochemical properties of its varieties were determined and consequently suggested possible industrial uses.

Material and Methods

Samples

Twenty kg of each variety of sweet potatoes, obtained from the indigenous community ASOBARI (Retiro de los Indios Association of Sweet Potato Producers) located in the Retiro de los Indios (Cereté-Colombia). Samples were washed with current water, manually peeled with commercial knives, sliced with a vegetables processor CA301 (SAMMIC, España) and immersed during 30 minutes into a sodium bisulfite solution 1500 ppm (1:3 w/v).

Obtained samples were liquefied using an industrial blender LC15 (JAVAR®, Bogotá D.C., Colombia) and immersed into a sodium bisulfite solution 1500 ppm (1:1 v/v), filtered and dried in an oven Thermolab (DIES, Itagüí, Colombia) at 50 °C for 24 hours. Sweet potato starch powder was attained pulverizing the granular material through a 100-mesh sieve. Samples were packed and sealed in polyethylene bags.

Starch analysis

Sweet potato starch was analyzed for moisture content according AOAC (2005) by an oven Thermolab (DIES, Itagüí, Colombia). PADES (2015) guide was used to determine amylose and amylopectin content by a spectrophotometer Spectroquant® Pharo 300 (Merck KGaA, Darmstadt, Alemania).

Starch color was determined according to Grace (1977). Starch granule size was calculated according PADES (2015) by using a sieve equipment CEL 313 (C.I M&M Instrumentos Técnicos, Medellín, Colombia). Gelatinization temperature was determined according Grace (1977), using a magnetic hot plate (Fisher Scientific Isotemp®, China).

Pasting properties were determined using a rheometer (Anton Paar, Austria), peak viscosity, gel breakdown, starch setback and cooking parameters were obtained from amylograph curves. Starch solubility, swelling volume and water absorption were calculated according Aristizabal and Sanchez (2007). Paste clarity was evaluated as transmittance according Craig et al. (1989) at 650 nm by a spectrophotometer GENESYSâ?¢ 10S UV-Vis (Thermo SCIENTIFIC, USA).

Statistical analysis

All analysis were carried out in triplicates and results were subjected to analysis of variance (ANOVA). Differences were considered significant at p < 0.05.

Results and discussion

Moisture content was 4.09% for Tainung and 3.17% for 199062-1 clone (p â?¤ 0.05). These values are lowest than previously reported by Acosta and Blanco (2013). In case of amylose content, Tainung g presented 23.21% whereas 199062-1 clone 22.92% (p â?¤ 0.05). Amylose and content values are also inferior to reported by Acosta and Blanco (2013). Sweet potato starch color depends on raw material characteristic, 199061-1 clone presented a whiter color than Tainung. Starch granule size of 199062-1 was larger than Tainung, with 30.15 µm and 16.80 µm respectively. Gelatinization temperature for both clones were similar, with 78.30 °C for Tainung and 78.50 °C for 199061-1 (p > 0.05).

In case of pasting properties behavior, initial viscosity for both clones was similar, with values of 9.90 and 10.24 cps for 199062-1 clone and Tainung respectively. Peak viscosity was 1994 for 199062-1 cps and 2206 cps for Tainung. Similar behavior was reported by Acosta and blanco (2013) for sweet potato starch and Aristizabal and Sanchez (2007) for cassava starch.

Gel breakdown and starch setback were 586 and 495 cps for 199062-1 clone and 830 and 352 cps for Tainung (p £ 0.05). These values were higher than previously reported by Hernandez et al. (2008), which indicates that starches from these sweet potato varieties could be an interesting alternative for food processing industry.

Cooking parameters values for 199062-1 and Tainung were 1.2 min for and 1.0 respectively (p > 0.05), which are in agreement with previously reported values by Aristizabal and Sanchez for cassava starch.

Samples presented starch solubility of 1.08% for Tainung and 1.30% for 199062-1 (p > 0.05), swelling volume for 199062-1 was noticeable higher than Tainung, with 14.53 g/g insoluble solids and 5.34 g/g insoluble solids respectively (p â?¤ 0.05). These values are in agreement with the previously reported by Aristizabal, and Sanchez (2007). Water absorption for 199062-1 was higher than Tainung, with 1.88 g of water/g of sample and 1.47 g of water/g of sample respectively (p â?¤ 0.05). For paste clarity, Tainung and 199062-1 sweet potato starches showed similar transmittance values (%T), 15.63% and 14.56% respectively (p > 0.05). These starches are considered as opaque, since transmittance was lower than 40% (Aristizabal and Sanchez, 2007). Obtained results were inferior to reported by Hernandez et al. (2008) with 24.64%T and Achille et al. (2007) with 20.7%T.

Conclusions

Sweet potato starches from Tainung and 199062-1 clones presented a similar starch content and physicochemical property that offers advantages in food processing industry. According to reduced values of paste clarity and remarkable capacity of forming strong and elastic gels, suggesting that can be employed as thickening and stabilizing agents in sauce, soup, pastry, ice cream and jellies industries.

References

Achille, T.F.; Georges, A.N.G.; Alphonse, K. Contribution to light transmittance modelling in starch media. African Journal of biotechnology, 6, pp. 569-575.

Acosta, A.P.; Blanco, C. (2013), Obtención y caracterización de almidones nativos colombianos para su evaluación como posibles alternativas en la industria alimentaria. Universidad de Cartagena. Cartagena, 50 pp.

AOAC. (2005), Official methods of analysis, 18^th ed. Washington DC. Association of Official Analytical Chemists.

Aristizabal, J.; Sanchez, T. Guía técnica para producción y análisis de almidón de yuca. Organización de las Naciones Unidas para la Agricultura y la Alimentación (FAO). Roma, 153 pp.

Collado, L.S.; Mabesa R.C.; Corke, H. (1999), Genetic variation in the physical properties of sweet potato starch. Journal Agric. Food Chemistry, 47, pp. 4195-4201.

Craig, S.A.S; Maningat, C.C.; Seib, P.A.; Hoseney, R.C. (1989), Starch paste clarity. Cereal Chem., 66 (3), pp.173-182.

Grace, M.R. 1977. Elaboración de la yuca. Organización de las Naciones Unidas para la Agricultura y la Alimentación (FAO). Roma, 116 pp.

Hernández, M; Torrueco, J; Chel, L; Betancur, D. (2008), Caracterización fisicoquímica de almidones de tubérculos cultivados en Yucatán, México. Ciência e Tecnología de Alimentos, 28 (3), pp. 718-726.

PADES (2015), Grupo de investigación en Procesos Agroindustriales y Desarrollo Sostenible. Universidad de Sucre. Sincelejo.

Teow, C.C.; Truong, V.; McFeeters, R.F.; Thompson, R.L., Pecota, V.; Yencho, G.C. (2007), Antioxidant activities, phenolic and β-carotene contents of sweet potato genotypes with varing flesh colours. Food Chemistry, 103, pp. 829-838.

Woolfe, J.A. (1992), â??Sweet potato an untapped food resourceâ?. Cambridge University Press. Cambridge, 643 pp.

Zhang; C.G. and Oates. (1999), â??Relationship between α-amylase degradation and physico-chemical properties of sweet potato starchesâ?. Food Chemistry, 65, pp. 157-167.