GRADING IN SWEET POTATO ‘KOKAN ASHWINI’

GRADING IN SWEET POTATO ‘KOKAN ASHWINI’

 

1. M. Shirke, R. G. Manjrekar and R. G. Khandekar,
2. Department of Horticulture, College of Agriculture, Dr, B. S. Konkan Krishi Vidyapeeth, Dapoli.

Dist. Ratnagiri (415 712) Maharashtra (India)

 

The present investigation was carried out in the Department of Horticulture, College of Agriculture, Dapoli, Dist-Ratnagiri, Maharashtra (India)., during year 1999-2000. Among all the grades of tuber, grade ‘B’ (medium size tubers 100-199 gms) was found to be most common grade in terms of weight (49.15 per cent) which also recorded 42.15% share by number. It was followed by grade C (small size tubers below 100 g) in terms of weight (39.28 per cent) and number (48.00 per cent). The physical parameters like weight, volume size of tuber, weight of flesh, peel and flesh to peel ratio showed statistically significant difference. The maximum weight (249.42 g) volume (237.71 ml), length (16.94 cm) dimeter (5.80 cm) girth (20.27 cm) of tuber, weight of flesh (239.00 gm), peel (14.42 g) was recorded by ‘A’ grade (200 g and above) tubers. Non significant differences were recorded for specific gravity. The chemical parameters of different grades like moisture and starch showed significant differences. The total sugar (2.21 per cent) and starch (20.77 per cent) was recorded maximum in ‘B’ grade. The maximum pH (5.95) and moisture content (67.27 per cent) was recorded by ‘A’ grade and ‘C’ grade respectively. Non significant differences were recorded for total solids pH and acidity. The organoleptic score recorded for three grades revealed that ‘A’ grade tubers ad better palatability than ‘B’ and ‘C’.

INTRODUCTION

Sweet potato is one of world’s highest yielding crops, with total food production per unit area exceeding that of rice and with higher value food. It is short duration crop rich in energy, carotenoids, dietrary fibre, minerals and vitamin C. Fresh tuber contains moisture 60.68 per cent, protein 1.07 per cent, fat 0.35 per cent, mineral matter 1.07 per cent and carbohydrates 31.41 per cent. Not only roots are rich in nutrients but also, the tender shoots of sweet potato as an important source of vegetable fibre and food. Studies in Taiwan has shown that tops contain total nutrients equivalent to beef or Park (Anon. 1982). Tops are very important as animal feed as highly succulent and digistable sweet potato vines contain appreciable amount of protein 8.5 to 19.5 per cent (Abdel Akher and Ghali 1966).

Sweet potato is generally cultivated for a period of 4-5 months depending upon agroclimatic conditions and varieties of the region. For Kokan region of Maharashtra State the short duration varieties like Sree Bhadra, Sree Vardhini and Kokan Ashwini has been recommended for cultivation. Kokan Ashwini a short duration variety of the region has good potential for preparation of processed products like jam, sauce, pickle, chips, powder, rava, candies, sweets. In the presents study the grading has been on weight basis so as to minimize post harvest losses. Their physical and chemical properties has been studied. To minimize post harvest losses and easy post harvest handling Badar (1990) graded Ratna and Kesar varieties of Mango into three grades. Similar type of work was done by Chachad (1995) in water melon (sugarbaby) fruits.

MATERIALS ANN METHODS

The present study on grading of Sweet potato tubers of Var. ‘Konkan Ashwini’ was under taken in the Department of Horticulture, College of Agriculture, Dapoli during 1999-2000.

Grading of tuber :

The matured sweet potato tuber (Var. ‘Konkan Aswini’) harvested under rainfed condition of the Konkan region of Maharashtra State were used for grading experiment. The matured tuber were categorized statically into  three grades as grade ‘A’ (200 g and above), grade ‘B’ (100-199 g) and grade ‘C’ (below 100 g). The range of medium size group was calculated by using formula mean = 1 x S.D. (Panse and Sukhatme, 1985).

Physical Characters :

The tubers of A, B and C grade were analysed for physical characters. The tubers were weighed in grams on monopan electric balance. The volume of the tubers was determined in ml by water displacement method using a measuring cylinder. Specific ravity of tuber was computed by dividing the value of fresh weight of tuber by that of volume (Sulladmath 1975). Length of tuber from stalk and to apex and diameter on the equatorial plane were determined in cm with the help of vernier caliper. The flesh weight in gms was weighed on electric balance. The peel of tuber was weighed on electric balance. Flesh to peel ratio was calculated by dividing flesh weight and peel weight values.

 

Chemical Composition:

The tubers of above mentioned grades were analysed for moisture, T.S.S., acidity, pH, reducing sugar, total sugar and starch after 7 days from harvesting.

The percentage of moisture was estimated bu oven drying a known weight of sample at 55-60⁰ C to a constant weight (A.O.A.C. 1975) and substracting the final weight from initial fresh weight and recorded in percentage. Starch from sweet potato tubers was determined by the procedures given by Kanwar and Chopra (1961). Total soluble solids were determined with the help of hard refractometer and the values were corrected to 20⁰ C with the help of temperature correction chart and recorded as Brix (A.O.A.C., 1975). Reducing and total sugars were determined by the method of Lane and Eynon (1923) Titratable acidity was determined by blending and suspending a known weight for sample in four times of its weight in boiled and cooled distilled water and titrating it against standard 0.1 N Naoll using phenolpththalein as an indicator. The pH of the pulp was determined using pH meter at 28⁰C. Sweet potato tubers from grades were organoleptically evaluated for colour, flavour and texture by a panel of judges who scored on a 9 point Hedonic sacale (Amerine et al. 1965).

RESULTS AND DISCUSSION

The data on per cent distribution of tubers (by weight and number) and average organoleptic score in different grades of tuber are presented in Table 1.

The medium size tubers by weight contributed half the tubers studied (49.15 per cent) followed by small size tubers and the lowest was contributed by large size (12.57  per cent) (Table 1). Out of total tubers studied number was recorded in maximum contribution (48.00 pen cent) by grade ‘C’ which was closely related to the contribution by grade ‘B’ i.e. medium size tuber (42.15 per cent) and minimum tubers by numbers by number were recorded in grade ‘A’ (Table 1). The results presented in Table 1 indicated that statistically significant differences were obtained in per cent distribution of sweet potato tubers by weight and small size grade by number was most common. These results are in agreement with those reported by Badar (1990 ) in Ratna and Kesar mango fruits and by Chachad (1995) in watermelon.

The average organoleptic score reorded for color, flavour and texture of graded sweet potato tuber revealed that, tubers of grade ‘A’ had better palatability than grade ‘B’ and ‘C’ (Table 1). Similar observations were also recorded by Paralkar (1985) and Sawant (1989) in graded sapota fruits.

The data on physical parameters of graded sweet potato tubers are presented in Table 2.

There was significant differences in weight of graded tubers. The maximum of which showed by grade A followed by ‘B’ and ‘C’ (Table 2). Significant maximum volume of tuber was recorded by grade ‘A’ (237.71 ml) followed by grade ‘B’ and minimum volume was recorded by grade ‘C’. Results on weight and volume of graded tubers are in argument with those obtained by Badar (1990) in Ratna and Kesar varieties of mango. The data on specific gravity of graded sweet potato tubers was more than 1. However no significant differences were obtained in specific gravity of sweet potato tuber (Table 2). The tubers in grade ‘A’ recorded significant maximum length (16.94 cm) diameter (5.80 cm)  and girth (20.27 cm) over grade B and C (Table 2). Corresponding results have also been obtained by Paralkar (1985) in Sapota. The tubers in grade ‘A’ also recorded significant maximum weight of flesh (239.00 g) weight of peel (14.42 g) and flesh to peel ration (17.04 :1) over grade B and C (Table 2).  Similar trends in observations were also recorded with respect to weight of pulp in graded sapota fruits by Sawant (1989).

The data on chemical composition of graded sweet potato tubers are presented in Table 3.

The data presented on moisture content in Table 3. revealed that maximum of moisture content was explained by grade ‘C’ (67.27 per cent) followed by grade ‘B’ (66.38 per cent) and minimum of which recorded in large grade tubers (65.47 per cent). The maximum moisture content exhibited by small graded could be attributed to better retention of moisture. The observations analogoas to this findings were recorded by Joshi (1983) in mango and Pawar (1988) in Karaonda fruits during storage at ambient temperature and cool chamber. The data on total soluble solids content did not show significant differences with respect to grades (Table 3). Above findings are in analogus with observations reported by Niak (1985) in Alphonso mango fruits. The total sugar content in graded sweet potato tubers differ significantly with respect to grades. The maximum of total sugar was recorded in medium size tuber (2.21 per cent) followed by large sized tubers (1.96 per cent) and minimum of which recorded by Chachad (1995) in water melon. The maximum total sugar content exhibited by medium size grade might be due to slow conversion of starch into sugars. The graded sweet potato tubers exhibited statistically significant differences with respect to starch content amongst the different grades. The maximum starch content was observed in medium size tubers (20.77 per cent) followed by large grade tubers (19.43 per cent) where as minimum starch content exhibited by small size tubers (17.60 per cent). The maximum starch into sugars. The above observations are in analogous with the observations reported by Naik (1985) in Alphonso mango. The acidity of graded sweet potato tubers did not show much variation among the different grades (Table 3). Also graded sweet potato tubers did not show much differences for pH values among different grades (Table 3). The above findings are in line with observations by Joshi (1983) in Alphonso mango fruits.

REFERENCES

Abdel A Kher, M. and Ghali, Y. 1966. The production of starch and flour from sweet potatoes. Annals of Agril. Sci. University of Ain. Shams. 11 (1) : 159-167. Amerine, M. A., Pangboran, R. M. and Roessier, B. B. 1965. Principles of Sensory Evaluation of Food. Academic Pres, London.

Anonymous 1982. Sweet potato. Proceedings of the first International Symposium Asian Vegetable Research and Development Centre, Shanhana, Thainan, Taiwan, China pp : 1-7.

 

A.O.A.C. 1975. Official Method of Analysis. II^nd edition. Association of official Analytical chemists Washington, D. C. 20044.

Badar, R. S. 1990. Studies on maturity indices, grading and storage of mango (Mangifera indica L.) fruits Cv. Ratna and Kesar. A M.Sc. (Agri.) thesis submitted to the Konkan Krishi Vidyaeeth, Dapoli, Dist. Ratnagiri Maharashtra State.

 

Chachad, S. S. 1995. Studies on maturity indices, some aspects of Post harvest handling and processing of watermelon (Citrullus lanatus (Thumb) matsum and Nakai) Cv. Sugar baby. A M.Sc. (Agri.) thesis submitted to the Konkan Krishi Vidyapeeth, Dapoli, Dist.Ratnagiri Maharashtra State.

Josti, G. D. 1983. Studies on changes in Alphonso mango (Mangifera indica L.) fruits during transport and storage. A Ph.D. thesis submitted to Indian Agricultural Research, Institute, New Delhi.

Kanwar, G. S. and Eynon, L. 1923. Determination of reducing sugars by Fehlings solution with methylene blue as an indicater J. Soc. Chem. Ind. 42 : 32.

Naik, S. K. 1985. Studies on physic-chemical changes in Alphonso and Ratna mango (Mangifera indica L.) fruits during growth, development and storage, A M.Sc. (Agri.) thesis submitted to the Konkarn Krishi Vidyapeeth, Dapoli, Dist.Ratnagiri Maharashtra State.

Panse, V. G. and Sukhatme, P. V. 1985. Statistical Methods for Agricultural Workers. 4^th Ed. I.C.A.R., New Delhi.

Paralkar, G. 1985. Studies on physic-chemical changes in Sapota (Manilkara achras (mill) forsber) Cv. Kalipatti fruits during growth, development and storage. A M.Sc. (Agri.) thesis submitted to the Konkan Krishi Vidyapeeth, Dapolim Dist.Ratnagiri Maharashtra State.

Pawar, C. D. 1988. Studies on post harvest handling and preparation of different products of Karonda (Carissa carandas L.) fruits. A M.Sc. (Agri.) thesis submitted to the Konkan Krishi Vidyapeeth, Dapolim Dist.Ratnagiri Maharashtra State.

Sawant, V. S. 1989. Studies on post harvest handling and preservation of Sapota (Manilkar achras (Mill) forsberg) fruit Var. Kalipatti A. M.Sc. (Agri.) thesis submitted to the Konkan Krishi Vidyapeeth, Dapoli, Dist.Ratnagiri Maharashtra State.

Sulladmath, V. V. 1975. Studies on fruit growth and development in sapota var. Kalipatti. A thesis submitted to Univ. of Agricultural Sciences, Bengalore, Karnataka.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1. Grading of sweet potato Var. Kokan Ashwini tubers on the basis of weight and number.

Sr. No.	Grade	Grade specification	Per cent distribution		Average organoleptic
			By weight	By numbers	Score
1.	A	200 g and above	12.57	9.85	8.57
2.	B	100-199 g	49.15	42.15	8.45
3.	C	Below 100 g	39.28	48.00	8.32
	General Mean		33.23	33.33	8.44
	S.E.+ –	1.95	1.95	0.51	0.014
	CD at 5 %		5.76	2.06	0.0043
	CD at 1 %		7.91	2.87

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2. Physical Characters Sweet potato tubers (Konkan Aswini ) as affected by different grades.

Particular	Grade A	Grade B	Grade C	General Mean	S.E.+        –	CD at 5 %	CD at 1 %
Weight of tubers (g)	249.42	151.57	74.14	158.37	3.38	10.05	13.76
Volume of tuber (ml)	237.71	148.14	66.42	150.75	3.64	10.28	14.08
Specific gravity	1.04	1.07	1.11	1.07	0.29	NS	NS
Length of tuber (cm)	16.94	14.27	9.07	13.41	0.51	1.51	2.07
Girth of tuber (cm)	20.27	16.47	12.05	16.26	0.40	1.19	1.61
Diameter of tuber (cm)	5.80	5.08	3.50	04.79	0.09	0.26	0.37
Weight of flesh (g)	239.00	124.00	63.14	142.04	7.91	23.50	32.19
Weight of peel (g)	14.42	9.57	7.71	10.56	0.65	1.98	2.64
Flesh to peel ratio	17.04:1	11.32:1	8.19:1	12.18:1	0.67	1.99	2.74

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3. Chemical composition of Sweet potato tubers (Konkan Aswini ) as affected by different grades.

Particular	Grade A	Grade B	Grade C	General Mean	S.E.+        –	CD at 5 %	CD at 1 %
Percent moisture content	65.47	66.38	67.27	66.37	0.17	0.51	0.69
TSS (0Brix)	4.27	4.27	4.26	4.26	4.24	NS	NS
Total Sugar (percent)	1.96	2.21	1.84	2.00	0.02	0.08	0.34
Starch (percent)	19.43	20.77	17.60	19.26	0.29	0.08	0.35
Acidity (percent)	0.031	0.032	0.031	0.031	0.0014	NS	NS
pH	5.95	5.79	5.86	5.87	0.085	NS	NS