Characterization of the content of reducing sugars, total sugars and starch in potato varieties and clones grown in Osorno-Chile Lucía De la Fuente a, Jennifer Varas a, Silvia Mendez a, Ma. Elita López b a Depto. de Ciencia y Tecnología de los Alimentos, Universidad de Los Lagos, Osorno, Chile, (ldelaf@ulagos.cl) b Centro de Análisis de los Alimentos, Universidad de Los Lagos, Osorno, Chile,(melopez@ulagos.cl) ABSTRACT The purpose of this study was to determine and quantify the content of reducing sugars, total sugars and starch in six varieties of potatoes (Yagana-INIA, Patagonia-INIA, Karu-INIA, Pukará-INIA, Ona-INIA, Puyehue-INIA) and three advanced clones (R91193-1, R89054-34 and RX90020-9), using Desirée like control. The material came from the Genetic Improvement Program at the Remehue INIA-CHILE from the 2009-2010 season. Samples were lyophilized in fresh and cooked states. The extraction of reducing sugars, total sugars and starch was carried out using a method standardized by the International Potato Center (CIP) in Peru, with slight modifications. The determination of reducing sugars was made directly after extraction with alcohol. For the determination of total sugars was necessary to do a hydrolysis with concentrated HCl for a period of 5 minutes in water bath at 65-70 ºC. For the determination of starch samples were subjected to acid hydrolysis with 5% HCl for a period of 4 hours in water bath at 100ºC. The quantification was performed using a 3.5 dinitrosalicylic acid spectrophotometric method. Applying Duncan test for multiple comparisons in the lyophilized cooked varieties 7 homogeneous groups in the starch content were observed, in the reducing sugars 5 were identified and in the total sugars 6 homogeneous groups were stablished. In the fresh lyophilized varieties 6 homogeneous groups were observed in starch content, 7 were recognized in the reducing sugars and 6 were seen in the total sugars. The fresh variety that contains higher starch content is the clone R89054-34 (16,07±0,18%). Puyehue-INIA had the highest content of reducing sugars and total sugars (1,11±0,08% and 1,57±0,03% respectively). The lower values of starch in fresh potato was for Pukará-INIA (13,2±0,07%); instead, the lower values of reducing sugars was found in Desirée (0,86±0,03%) and total sugars was found in Ona-INIA with 1,17±0,03%. This characterization will select varieties according to their technological skills, especially to prevent the use of specimens with high values of reducing sugars in fried and other heat treatments, as they tend to the Maillard reaction, which damage the potatoes characteristic colour and flavour. Keywords: potatoes; reducing sugars; starch, dinitrosalicylic acid; spectrophotometric method INTRODUCTION The influence of chemical composition during the industrial potato processing is of great importance to maintain the quality of potato products (Singh et al, 2009). The dry matter and high starch contents are the most significant components for the processing industry. Other components that directly influence the quality and classification of varieties for different industrial processes are: glucose, fructose and sucrose, these being the most important sugars and the ones found in greater amounts in the tuber flesh (Amrein et al, 2003 and Lisinska & Leszczynski., 1989). The purpose of this study was to determine and quantify the content of reducing sugars, total sugars and starch in six varieties of potatoes (Yagana-INIA, Patagonia-INIA, Karu- INIA, Pukará-INIA, Ona-INIA, Puyehue-INIA) and three advanced clones (R91193-1, R89054-34 and RX90020-9), using Desirée like control. The material came from the Genetic Improvement Program at the Remehue INIA-CHILE from the 2009-2010 season.
MATERIALS & METHODS The crops were grown on the premises of INIA-Remehue, located 8 km north of the city of Osorno. Latitude 40 31' 13, 97'' S, Longitude 73 3' 53, 06'' W. Production began in October 2009 and the harvest began in March 2010. The crops were grown on volcanic ash soil type (soil quality with high levels of organic matter characteristic of the area), with certified INIA seeds. A preemergence herbicide application was conducted for growth. Late blight fungicides, food nitrogen-based fertilizers, Potassium and phosphorus were also used. The potatoes were stored in plastic boxes with 25 to 35 Kg capacity, in closed warehouses and dark environment at an initial temperature of 4-7 C, reaching 12 C as time went by. Three replicas of 18 tubers for each variety were analysed and were lyophilized in fresh and cooked states. The dry matter determined through thermogravimetric method. The extraction of reducing sugars, total sugars and starch was carried out using a method standardized by the International Potato Center (CIP) in Peru, with slight modifications. The determination of reducing sugars was made directly after extraction with alcohol. For the determination of total sugars was necessary to do a hydrolysis with concentrated HCl for a period of 5 minutes in water bath at 65-70 ºC. For the determination of starch samples were subjected to acid hydrolysis with 5% HCl for a period of 4 hours in water bath at 100ºC. The quantification was performed using a 3.5 dinitrosalicylic acid spectrophotometric method (DNS) at 490 nm, using glucose as standard. RESULTS & DISCUSSION The Table 1 and Figure 1shows the content of reducing sugars, total sugars and starch in potato varieties and clones grown in Osorno-Chile, in variety and clones in fresh state expressed in base wet in the top of table and in cooked state expressed in base wet in the bottom of table. Applying Duncan test for multiple comparisons in the fresh lyophilized varieties 6 homogeneous groups were observed in starch content, 7 were recognized in the reducing sugars and 6 were seen in the total sugars. In the lyophilized cooked varieties 7 homogeneous groups were observed in the starch content, and 5 in the reducing sugars. Table 1. Content of reducing sugars, total sugars and starch in potato varieties and clones grown in Osorno-Chile, 2009-2010 season. Varieties and clones % Dry Matter % Starch (g/100 g fresh) % Reducing sugars (g/100 g fresh ) % Total sugars (g/100 g fresh) Content in fresh states Desirée 17,6 ± 0,44 10,35 ± 0,36 f 0,86 ± 0,03 b 0,94 ± 0,03 c Patagonia-INIA 17,1 ± 0,48 11,55 ± 0,35 e 0,58 ± 0,07 cd 0,64 ± 0,06 d Puyehue-INIA 20,7 ± 1,67 12,83 ± 0,16 c 1,11 ± 0,08 a 1,57 ± 0,03 a Yagana-INIA 18,1 ± 0,77 12,19 ± 0,41 d 0,23 ± 0,01 f 0,29 ± 0,01 f Ona-INIA 18,7 ± 0,24 12,07 ± 0,17 d 0,64 ± 0,02 c 1,17 ± 0,03 b Karu-INIA 15,2 ± 0,17 10,72 ± 0,19 f 0,35 ± 0,01 e 0,33 ± 0,02 e Pukará-INIA 19,9 ± 0,06 13,54 ± 0,07 b 0,2 ± 0,01 g 0,28 ± 0,01 f RX90020-9 17,7 ± 0,67 12,26 ± 0,21 d 0,62 ± 0,06 c 0,62 ± 0,05 d R89054-34 23,8 ± 0,73 16,07 ± 0,18ª 0,51 ± 0,04 d 0,65 ± 0,04 d R91193-1 18,7 ± 0,41 12,33 ± 0,10 cd 0,57 ± 0,003 c 1,06 ± 0,04 c Content in cooked states Desirée 22,2 ± 1,36 15,47 ± 0,29 b 0,43 ± 0,03 c 0,59 ± 0,04 de Patagonia-INIA 17,1 ± 1,07 11,28 ± 0,45 f 0,80 ± 0,10 a 1,31 ± 0,10 b Puyehue-INIA 19,7 ± 0,07 13,72 ± 0,13 c 0,36 ± 0,03 cd 0,66 ± 0,04 d Yagana-INIA 20,3 ± 0,41 13,52 ± 0,01 c 0,72 ± 0,01 ab 1,38 ± 0,03 a Ona-INIA 19,1 ± 0,25 13,12 ± 0,12 d 0,30 ± 0,01 de 0,39 ± 0,003 g Karu-INIA 18,5 ± 0,49 12,81 ± 0,16 e 0,26 ± 0,02 e 0,33 ± 0,02 g Pukará-INIA 20,6 ± 0,15 14,03 ± 0,06 c 0,66 ± 0,01 b 0,74 ± 0,03 c RX90020-9 17,5 ± 0,35 9,18 ± 0,05 g 0,43 ± 0,04 c 0,47 ± 0,02 f R89054-34 22,4 ± 1,27 15,92 ± 0,28 ab 0,44 ± 0,06 cd 0,52 ± 0,05 ef R91193-1 21,7 ± 0,9 16,13 ± 0,22 a 0,28 ± 0,01 e 0,39 ± 0,01 g
Content of starch in fresh states, (g/100g). Content of starch in cooked states, (g/100g). Content of reducing sugars in fresh states, (g/100g). Content of reducing sugars in cooked states, (g/100g). Content of total sugars in fresh states, (g/100g). Content of total sugars in cooked states, (g/100g). Note: Difference fonts indicate significant differences between varieties, p< 0,05. Figure 1: Content of reducing sugars, total sugars and starch in potato varieties and clones (wet basis) grown in Osorno-Chile, 2009-2010 season. The fresh variety that contains higher starch content is the clone R89054-34 (16,07±0,18%). The Puyehue- INIA had the highest content of reducing sugars and total sugars (1,11±0,08% and 1,57±0,03% respectively). The lower values of starch in fresh potato was for Pukará-INIA (13,2±0,07%); instead, the lower values of reducing sugars was found in Desirée (0,86±0,03%) and total sugars was found in Ona-INIA with 1,17±0,03%. Hasbún, J. et al (2009) and Liu, Q. et al (2007) show the starch results are in the 13.4 and 20.8 g/100 g fresh (raw skinless samples) range. The latter used the method described by Megazyme for determination of reducing sugars and the method described by Nielsen for the determination of starch.
Loyola, N., et al (2010), specifically analyzed the starch content in the Desirée variety through the Munson and Walker method, getting a 13.79 g/100g fresh level. In its cooked state and expressed on wet basis, the the starch results vary in the 9.18 ± 0.05 and 16.13 ± 0.22 g/100 g range, corresponding to the RX90020-9 and R91193-1 clones respectively. Regarding reducing sugars, Hasbún, et al (2009) indicates a 0.076 and 1.384 g/100 g fresh range. Another study by Gallego, E.M., et al (2006) shows a smaller range that varies between 0.11 and 0.24 g/100 g fresh. Analyses were conducted using the dinitrosalicylic acid method (DNS) and considers the study of seven varieties among which is Desirée with a level of 0.13 ± 0.01 g/100 g fresh. Loyola, N., et al (2010) specifically points a 0.13 g/100 g fresh level to the Desirée variety, analyzed by the Munson and Walker method. In its cooked state and expressed on wet basis, the reducing sugars results vary in the 0.26 ± 0.02 and 0.8 ± 0.10 g/100 g range, corresponding to the Karú and Patagonia varieties respectively. In its raw state and expressed on wet basis, the total sugars results are in the 0.28 ± 0.01 and 1.57 ± 0.03 g/100 g range, corresponding to the Puyehue and Pukará varieties respectively. The study by Loyola, N., et al (2010) points to the Desirée variety a 0.2 g/100 g fresh level, analyzed by the Munson and Walker method. In its cooked state and expressed on wet basis, the total sugars results vary in the range of 0.33 ± 0.02 and 1.38 ± 0.03 g/100 g, corresponding to Yagana and Karú varieties respectively. The Table 2 shows the difference between the starch, reducing sugars and total sugars content values obtained in its fresh and cooked states. The results show variations between 0 and close to 5 %. Table 2: Comparison between the starch, reducing sugar and total sugars contents in fresh and cooked samples expressed in wet basis. Varieties and clones Differences between Fresh and Cooked Potatoes (%) Starch Reducing sugars Total sugars R89054-34 -0,15-0,07-0,13 Pukará 0,49 0,46 0,47 Puyehue 0,89-0,75-0,90 R91193-1 3,80-0,29-0,67 RX90020-9 -3,08-0,19-0,16 Yagana 1,33 0,49 1,09 Ona 1,05-0,34-0,78 Patagonia -0,27 0,22 0,67 Karú 2,09-0,09 0,00 Desirée 5,12-0,43-0,35
CONCLUSION This characterization will select varieties according to their technological skills, especially to prevent the use of specimens with high values of reducing sugars in fried and other heat treatments, as they tend to the Maillard reaction, which damage the potatoes characteristic colour and flavour. It is important to emphasize the characterization of the clones in this study, proving to be very good quality genotypes, with high starch and dry matter content and significant reducing sugar values. We must pay close attention to these genotypes and consider potential varieties that in the near future may contribute to the industry and help achieve a better use of the potato market by minor and large farmers. REFERENCES [1] Singh. J & Kaur. L. (2009). Advances in Potato Chemistry and Technology [online]. Elsevier Inc., pp 1-2. Available at: http://books.google.com/books?id=j6cmaxf6ofoc&printsec=frontcover&hl=es&source=gbs_ge_summary_r&cad=0 #v=onepage&q&f=false [2010, July] [2] Lisinska and Leszczynski. W. (1989). Potato Science and Technology [online]. Elsevier Science Publishers, pp 11-12, 19-20, 23, 26-27, 24-25, 34-35, 36-37, 32-33. Available at: http://books.google.com/books?id=wyt1s7qhn4sc&printsec=frontcover&hl=es&source=gbs_ge_summary_r&cad =0#v=onepage&q&f=false [2010, July] [3] Amrein, T.M., Schiónbochler. B., Rohner, F., Lukac, H., Schneider, H., Keiser, A., Escher, F., Amada, R. (2004). Potential for acrylamide formation in potatoes: data from the 2003 harvest [online]. European Food Research & Technology 219: 572-578. Available at: http://www.springerlink.com/content/egxcdq3ufvtkvr51/ [2010, September] [4] Hasbún, J., Esquivel, P., Brenes, A., Alfaro, I. (2009, Octubre). Propiedades físico-químicas y parámetros de calidad para uso industrial de cuatro variedades de papa. Revista Agronomía Costarricense [online], Nº 33, pp 79, 83.Available at: http://www.mag.go.cr/rev_agr/v33n01-077.pdf [2010, Agosto] [5] Loyola, N., Oyarce, E., Acuña, C. (2010). Evaluación del contenido de almidón en papas (Solanum tuberosum, SP. tuberosum CV. Desirée), producidas en forma orgánica y convencional en la provincia de Curicó, Región del Maule [online]. Scielo Chile, IDESIA (Chile), Vol. 28, Nº 2, Mayo-Agosto, 2010, pp 41-52. Available at: http://www.scielo.cl/scielo.php?pid=s0718-34292010000200005&script=sci_arttext [2010, Octubre] [6] Gallego, E.Ma., Miguez, M., De la Montaña, J. (2006). Aptitud de variedades de patata para su transformación en barritas prefritas, [online]. Ciencia y Tecnología Alimentaria, 2006, Vol. 5, Nº 003. Sociedad Mexicana de Nutrición y Tecnología de Alimentos, Reynosa, México, pp. 189-194. Available at: http://redalyc.uaemex.mx/pdf/724/72450304.pdf [2010, Octubre] [7] Liu. Q., Tarn. R., Lynch. D., Skjodt. N. (2007). Physicochemical properties of dry matter and starch from potatoes grown in Canada [online]. ScienceDirect, Food Chemistry 105 (2007), pp 898-900. Available at: http://www.sciencedirect.com/science?_ob=articleurl&_udi=b6t6r-4nkxwrj- 3&_user=3685540&_coverDate=12%2F31%2F2007&_alid=1500001475&_rdoc=1&_fmt=high&_orig=search&_or igin=search&_zone=rslt_list_item&_cdi=5037&_sort=r&_st=13&_docanchor=&view=c&_ct=112&_acct=c000061 143&_version=1&_urlVersion=0&_userid=3685540&md5=512582a9b5d99777e67547b867729725&searchtype=a [2010, Septiembre] ACKNOWLEDGEMENTS Consorcios Tecnológicos Empresariales de Investigación. FIA Papa Chile. FIC-CS-C-2005-1-A-006, P3, y Vicerrectoría de Investigación y Postgrado de la Universidad de Los Lagos.