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Cucurbit Genetics Cooperative Report 13:43-44 (article 16) 1990

Nutrients in Seeds of Edible Watermelon (Citrullus lanatus (Thunb.) Matsum. and Nakai)

Kechi Ma

Department of Horticulture, Gansu Agricultural University, Lanzhou, China (PRC)

Xing-ping Zhang and Ming Wang

Department of Horticulture, Northwestern Agricultural University, Yangling, Shaanxi, China (PRC)

Although there are other processed products from the flesh of edible seed watermelons in China, the main purpose is seed production. The seeds are roasted and eaten, with or without salting. Therefore, the economic value of these watermelons is dependent upon seed yields and nutrient values. A clear understanding of the nutrient make-up of seeds and their diversity among accessions are of practical importance for improvement of seed quality.

In 1987, dry seeds, with the seed coats removed, from three edible watermelon seed accessions (SW-1 and SW-2 with white-black seed coats, and SW-3 with red seed coats) were tested for nutrient content. Seeds were evaluated for amount of crude protein and fat, 17 amino acids, and fatty acid composition. Determinations were performed at the Center Laboratory at Northwestern Agricultural University. Analyses of crude protein and fat, amino acids, and fatty acids were determined on a MRK MR-150 KJEL auto nitrogen and protein analyzer, a MRK FATEX-P fat extractor, a BEKMAN 121MB amino acid analyzer, and a HITACHI 663-30 gas chromatograph, respectively.

The results of the crude protein and fat analyses are shown in Table 1. Similar analyses were previously reported for African and common watermelon accessions (1). The crude protein content of the edible seed lines in this test were much lower than were found in the seeds of the African lines (33.9 to 43.6%). However, the crude fat content in the edible seeds is similar to the African accessions (37.7 to 46.8%). Fatty acid composition of the edible seed revealed a very high proportion of the essential fatty acid, linoleic acid (C18:2) (Table 2). The proportion of linoleic acid in accessions SW-2 and SW-3 is much higher than the high quality plant oils from soybean (52.2%) and sesame (43.7%) (2). The very high proportion of the unsaturated linoleic acid in edible watermelon seed could provide a nutritious new source of the fatty acid used in the reduction of cholesterol and the prevention of arteriosclerosis in humans. In addition, edible watermelon seeds contain significant amounts of the essential amino acids (Table 3).

Even though the number of accessions of edible watermelon seed studied were limited, diversity in nutritive characters was observed. The greatest diversity was found in total fat content (38.6% to 47.9%) and the proportion of linoleic acid (31.17 to 72.98%). This shows us there is a high potential for genetic improvement of nutrients in edible watermelon seed.

Table 1. The crude protein and crude fat contents (%) of seed of edible seed watermelon.

Accessions

Crude Protein

Crude Fat

SW-1

26.77

38.69

SW-2

28.15

44.39

SW-3

27.69

47.93

Table 2. The fatty acid components and their proportions (%) of edible seed watermelon seeds.

Accessions

C14:0

C16:0

C16:1

C18:0

C18:1

C18:2*

C18:3*

SW-1

0.6

33.28

0.98

14.90

15.32

31.17

2.07

SW-2

trace

10.03

trace

3.18

9.46

77.33

none

SW-3

0.22

10.56

trace

4.19

12.44

72.98

none

*Essential fatty acids.

Table 3. The amino acid content of edible seed watermelon seeds (g/100g).z

Amino Acids

SW-1

SW-1

SW-3

Asp

3.334

3.211

3.003

Thr*

1.826

1.724

1.641

Ser

1.736

1.430

1.398

Glu

6.646

6.442

6.278

Pro

3.005

1.665

1.751

Gly

1.803

1.761

1.677

Ala

1.904

1.499

1.502

Cys

0.299

0.296

0.286

Val*

1.904

1.759

1.616

Met*

0.337

0.249

0.343

Ileu*

1.439

1.486

1.333

Leu*

2.530

2.164

2.036

Tyr

0.733

0.899

0.894

Phe

1.508

1.696

1.627

Lys*

1.142

1.088

0.960

His*

1.080

0.843

0.679

Arg*

6.662

4.980

4.796

*Essential amino acids.
zAmino acid grams in 100 grams of sample.

Literature Cited

  1. Wang, Ming and Xing-ping Zhang. 1988. Evaluation and utilization of the valuable African watermelon germplasm. Journal of Fruit Science 5(3):109-115.
  2. Wang, Ming. Nutrients of Food. (Book of Chinese).
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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 14 December, 2009