Nutrient composition of strawberry genotypes cultivated in a horticulture farm

Food Chemistry 199 (2016) 648–652

Contents lists available at ScienceDirect

Food Chemistry journal homepage: www.elsevier.com/locate/foodchem

Nutrient composition of strawberry genotypes cultivated in a horticulture farm Ashrafi Hossain a, Parveen Begum b, M. Salma Zannat c, Md. Hafizur Rahman a, Monira Ahsan d, Sheikh Nazrul Islam b,⇑ a

Sher-e-Bangla Agriculture University, Dhaka 1207, Bangladesh Institute of Nutrition and Food Science, University of Dhaka, Dhaka 1000, Bangladesh Soil Resource Development Institute, FarmGate, Dhaka 1215, Bangladesh d Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Dhaka, Dhaka 1000, Bangladesh b c

a r t i c l e

i n f o

Article history: Received 1 April 2013 Received in revised form 5 December 2015 Accepted 11 December 2015 Available online 12 December 2015 Keywords: Nutrient composition Strawberry genotypes Bangladesh

a b s t r a c t This article decribes the nutrient composition of four strawberry genotypes cultivated at the Sher-eBangla Agriculture University horticulture farm in Dhaka (Bangladesh). AOAC and standard validated methods were employed to analyse the nutrient composition. Protein, fat and ash contents were found to be vary significantly (LSD < 0.05), while the variation in moisture (LSD < 1.33), dietary fibre (LSD < 0.15) and total sugar (LSD < 0.09) were found to be insignificant among the genotypes. Vitamin C content ranged from 26.46 mg to 37.77 mg per 100 g edible strawberries (LSD < 0.060). Amount of carotenoids were found to be very low being in a range of 0.99–3.30 lg per 100 g edible fruit. Analysis of mineral revealed that strawberry genotypes contained a wide array of minerals including Ca, Mg, Na, K, P, Mn, Zn, Cu and Fe; most of which varied significantly (LSD < 0.05) among the genotypes. Strawberries could be a potential dietary supplement for vitamin C along with minerals, particularly for the children who do not like local fruits, but love to eat the colourful strawberries. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction Strawberries are a nutritious fruit with putative health benefits, because of their rich content of nutrients, with unique colour, flavour and taste (Giampieri et al., 2012; Mahmood et al., 2012; Marinova & Ribarova, 2007). They are consumed widely fresh or in processed forms assorted with dairy products. Fruits and vegetables are a potential source of vitamins and minerals, which are essential for human health. Many epidemiological studies support that a diet rich in fruits and vegetables is associated with a lower incidence of many chronic diseases, including diabetes, infections, cardiovascular and neurological disorders and cancers (Johnsen et al., 2003; Vauzour, Vafeiadou, Pendeiro, Corona, & Spenser, 2010). Strawberries are a natural source of micronutrients such as vitamin C, minerals, folates, and some important phytonutrients (Giampieri et al., 2012; Mahmood et al., 2012; Marinova & Ribarova, 2007). Strawberries are the most popular berries in the world. There are over 20 species and 600 varieties of strawberries that vary in

⇑ Corresponding author. E-mail addresses: [email protected], [email protected] (S.N. Islam). http://dx.doi.org/10.1016/j.foodchem.2015.12.056 0308-8146/Ó 2015 Elsevier Ltd. All rights reserved.

their colour, flavour, size and texture (Mondal, 2010). Nutrient composition of strawberries differs by cultivar and variety, cultivation technique and area, and climate as well as harvesting time and ripeness (Hakala, Lapveteläinen, Huopalathi, Kallio, & Tahvonen, 2003; Mahmood et al., 2012; Recamales, Medina, & Hernanz, 2007). Some varieties of strawberries are now cultivated in Bangladesh (BSS, 2014; Hossain, 2010). A few genotypes of strawberry were developed at the Sher-e-Bangla Agriculture University horticulture farms in Dhaka (Bangladesh) (Emdad, Baten, Hossan, & Hossain, 2013; Islam, Hossan, Ahsan, Mehraj, & Jamal Uddin, 2013). The present study reports the nutrient composition of four such strawberry genotypes. 2. Materials and methods 2.1. Reagents The analytical grade acetone, petroleum ether, butylated hydroxytoluene (BHT), metaphosphoric acid, sulphuric acid, nitric acid and perchloric acid were procured from Merck (Darmstadt, Germany). Ascorbic acid, 2,4-di-nitrophenyl hydrazine, all transb-carotene and mineral standards were obtained from Sigma Chemical Co. (St. Louis, MO, USA).

649

A. Hossain et al. / Food Chemistry 199 (2016) 648–652

2.2. Materials 2.2.1. Genotype cultivation and characterisation Four strawberry genotypes (Fragaria x ananassa) were developed and grown at the Sher-e-Bangla Agricultural University horticulture farm (Dhaka, Bangladesh) (23°480 N 90°240 E with an elevation of 8.2 m, http://www.worldatlas.com/aatlas/findlatlong. htm). The berries were collected for analysis of nutrient composition. The genotypes were characterised by growth and reproductive parameters, fruit structrures and morphological features (Emdad et al., 2013), which are summarised in Table 1. Specimens of each germplasms were collected from different nurseries. The strawberries were gown in a randomized complete block design with three blocks (size-2 m  1 m each) from November 2009 to March 2010. The blocks were exposed to sun for one week. Land was harrowed, ploughed and cross-ploughed three times, followed by laddering to obtain a good tilth. Cowdung, urea, TSP, MOP, zypsum and boron were applied at the rate of 10 tonnes, 150 kg, 120 kg, 150 kg, 10 kg and 3 kg per hector respectively. All the cowdung, TSP and half of MOP, zypsum and boron were applied at the time of land preparation. Urea and rest half of MOP were applied in two instalments at 30 and 50 days after planting. Seedlings were planted in such a way that the crown remained shallow. Irrigation, gap filling, weeding and top dressing were undertaken for better growth and development of the strawberry plants. 2.2.2. Sampling and processing Strawberries were harvested at commercial ripeness (>75% of the surface showing red colour). Approximately 300 g fruit from each genotype were collected in triplicate, placed in autoseal polybags and were taken to the laboratory at the Institute of Nutrition and Food Science (University of Dhaka, BD). Fruits were washed with demineralized water, and after removing surface water, air dried. The sepals were dissected with a knife and mashed in a glass mortar with a pestle cleansed previously with demineralized water. 2.3. Analysis of proximate nutrients Moisture content was determined by measuring the amount of water removed from the freshly processed fruit (5.0 g) following direct heating in an air oven at 100–105 °C until a constant weight was achieved (AOAC, 1998a). Protein was estimated by determination of nitrogen content using the Micro-Kjeldahl method and calculated using the total nitrogen conversion factor 6.25 (AOAC, 1998b). Analysis of nitrogen content comprised digestion of dried strawberry samples (1.0 g) in an auto-digestor and distillation in an auto-distillation (Autometic digestion_distilation unit, VELP Scientifica srl, Usmate Velate (MB), Italy) before titration using a burette. Fat. A Soxhlet extractor using petroleum ether was used to estimate total fat in the fruits (AOAC, 1998c).

Ash. An amount of 0.5 g dried strawberry powder was heated in a Muffle furnace (CARBOLITE, 1100 °C, Chamber Furnace, ELF models, England) at 600 °C for 3 h to determine a value for ash (AOAC, 1998d), which was calculated from the weight difference. Dietary fibre was analysed using a total dietary fibre assay kit (TDF-100A, Sigma–Aldrich, Saint Louis, USA). Carbohydrate in the strawberries was determined by difference (Raghuramulu, Madhavan, & Kalyanasundaram, 2003), where moisture, protein, fat, ash and dietary fibre contents were subtracted from the total weight of strawberry. Total sugar was determined using the method of Lane and Eynon and Fehling’s solution as described by AOAC (1998e). 2.4. Analysis of vitamin C Vitamin C content was estimated using spectrophotometric method with 2,4-dintrophenylhydrazine as an indicator (AOAC, 1998f). Freshly processed fruit (1 g) was homogenised in a mortar with a pestle with metaphosphoric acid (5% metaphosphoric acid in 10% acetic acid solution in water), filtered and treated with 85% sulphuric acid solution and 2,4-dintrophenylhydrazine, and then incubated at 60 °C for 60 min in a water bath. Absorbance was measured at 520 nm in a spectrophotometer (UV-1601, UV–Visible, Shimadzu Corp. Japan) for estimation of vitamin C in the fruits. 2.5. Analysis of carotenoids Total carotenoids content was determined, following acetone– petroleum-ether extraction, using a spectrophotometric method (Rodrizues-Amaya & Kimura, 2004). The carotenoids were extracted by grinding the processed fruit (2 g) in a mortar with a pestle and cold acetone. The mixture was passed through a sintered glass filter under vacuum, and the carotenoids were separated from the acetone using petroleum ether in a separating funnel. The petroleum eluent was adjusted to a specific volume with petroleum ether and absorbance was measured at 450 nm in a spectrophotometer (UV-1601, UV–Visible, Shimadzu, Tokyo, Japan). All-trans-b-carotene (Sigma Chemical Co., USA) was used as standard. 2.6. Analysis of minerals Mineral concentrations in the strawberry genotype were analysed using an atomic absorption spectrophotometric method (Petersen, 2002). Dried fruit samples (0.5 g) were subjected to wet digestion with nitric acid and perchloric acid (2:1 ratio) in an auto-digestor (Autometic digestion_distillation unit, VELP Scientifica srl, Usmate Velate (MB), Italy) at 325 °C to release mineral from the fruit matrix. After appropriate dilution, samples were aspirated into an air-acetylene flame to burn the elements into atomic components, the absorbance of which were measured

Table 1 Characteristic of strawberry genotypes cultivated at the horticulture farm in Sher-e-Bangla Agriculture University. Strawberry genotype

Growth parameters Plant height (cm)

Leaf area (cm2)

No. of runner plant1

Days to 1st flower budding

No. of buds plant1

Days to flower anthesis

No. of flowers plant1

Length of pedicel (cm)

No. of fruits plant1

Wt. of fruit (g)

Yield plant1 (g)

Days to harvesting

FA FA FA FA

37.07A 32.9bC 34.53AB 35.00AB

66.77A 47.43C 56.07B 63.6AB

38A 22C 12E 27B

51.33B 58.67A 52.33B 52.00B

27.00A 22.67BC 26.00AB 26.33AB

60.67B 69.33A 62.33B 62.33B

25.33A 16.33B 23.67A 24.67A

1.93B 1.46B 1.80B 2.83A

24.00A 23.33AB 12.67C 22.33AB

63.20A 62.00A 52.90B 60.40A

330.00A 318.00A 202.67B 308.33A

111.33C 127.00A 118.33C 119.67B

01 02 03 06

Reproductive parameters

Fruit structure

All of the characteristics vary at significant level (p > 0.05). Letters in superscript indicate about the statistical differences among the strawberry genotypes.

650

A. Hossain et al. / Food Chemistry 199 (2016) 648–652

in a spectrophotometer at appropriate wavelengths. Concentrations of calcium, magnesium, sodium, manganese, zinc, copper and iron were determined by atomic absorption spectrophotometry (Model-AA-7000S, Shimadzu, Tokyo, Japan). Potassium content was analysed by flame photometry (Jenway flame photometer model PFP7, Origin UK) and phosphorous was measured with spectrophotometry (UV-1601, UV–Visible, Shimadzu, Tokyo, Japan). A standard calibration curve was prepared for each of the minerals using the respective standard (Sigma Chemical Co., USA). 2.7. Data quality The accuracy and precision of data were tested, in order to validate the method and determine data quality, by carrying out inter-laboratory analysis of total carotenoids of FA 02 strawberry in the laboratories at the Institute of Nutrition and Food Science, University of Dhaka and at Nutritional Biochemistry section of the International Centre for Diarrheal Disease and Research, Bangladesh using an internal standard. SRM zinc (SRM 1568a rice flour, National Institute of Standards and Technology-NIST, Gaithersburg, MD 20899-8392, USA) was used for validation of mineral values. Estimated SRM zinc values were 19.36 and 18.70 mg per kg against the assigned value 19.4 ± 0.5 mg per kg. Samples were analysed in triplicate for each genotype and for every nutrient. 2.8. Statistical analysis Descriptive statistics were calculated, such as mean and standard deviation, for all nutrient data obtained. Duncan’s Multiple Range Test (DMRT) (Gomez & Gomez, 1984) using the MSTAT-C computer package program was used to test the mean difference of nutrients among the genotypes. It was expressed by least significant difference (LSD) test at 5% level of significance. 3. Results and discussion 3.1. Proximate composition Table 2 describes the proximate nutrients, vitamin C and total carotenoids content in the various strawberry genotypes. Moisture content ranged from 90.58 ± 2.75 to 92.17 ± 2.93% edible flesh, which is in line with results reported elsewhere (Giampieri et al., 2012; Recamales, Medina, & Hernanz, 2007). Protein values were estimated between 0.53 ± 0.15 g to 1.17 ± 0.08 g per 100 g edible strawberries, which is consistent with the report of Giampieri et al. (2012). Fat contents (0.33 ± 0.08 g to 0.48 ± 0.07 g/100 g edible) were also similar to those of Giampieri et al. (2012). However, these values are less than those reported by Recamales et al. (2007).

Ash values were noted to be 0.56 ± 0.09 g to 0.81 ± 0.17 g per 100 g edible fruit, which is higher than the reported values elsewhere (Giampieri et al., 2012; Recamales et al., 2007). Dietary fibre was in the range of 2.24 ± 0.47 g to 2.43 ± 0.29 g per 100 g edible fruits, which is higher than that reported by Giampieri et al.(2012). These variations in ash and dietary fibre may be due to regional factor or others as documented elesewhere (Mahmood et al., 2012). Amounts of total sugars (3.77 ± 0.25 g to 6.96 ± 0.71 g per 100 g edible fruits) were similar to reported data (Crespo, Bordonaba, Terry, & Carlen, 2010; Giampieri et al., 2012; Recamales et al., 2007). Thus, the proximate composition of strawberry genotypes developed in the horticulture farm resembles those of other varieties growing in different global regions. 3.2. Vitamin C and carotenoids composition Vitamin C content was estimated to be in a range of 26.46 ± 1.31 mg to 37.77 ± 2.72 mg per 100 g edible strawberries (Table 2). It was highest in FA 06 and lowest in FA 03 genotypes. These values are comparable with, or even higher than, those described for some genotypes grown at Swiss production sites (Crespo et al., 2010), but much less than that reported (58.8 mg per 100 g edible) for strawberries cultivated in some other regions of the world (Giampieri et al., 2012). However, it is to be noted that, amounts of vitamin C in the strawberry genotypes were comparable to those in the most expensive grape fruit (29 mg per 100 g edible) or pineapple (27.82 mg per 100 g edible), and much higher than those in local mango (10.88 mg per 100 g edible portion) or in most minor fruits (Islam, Khan, & Akhtaruzzaman, 2010, 2012; Shajib et al., 2013). The daily requirement of ascorbic acid, for preventing clinical symptoms of scurvy, is about 10 mg or less (Food, 1998). Therefore, potentially, daily intake of a single strawberry could prevent this disorder, particularly for children who do not like local fruits but love to eat the strawberry. Total carotenoids were found to be very little or insignificant (0.96 ± 0.17 lg and 3.30 ± 0.51 lg carotenoids per 100 g edible fruit, Table 2), which is less than the Bulgarian strawberry (Marinova & Ribarova, 2007). 3.3. Mineral composition Analysis of minerals revealed that the strawberry genotypes were rich in a wide variety of minerals including Ca, Mg, Na, K, P, Mn, Zn, Cu, and Fe (Table 3); most of which varied significantly (LSD < 0.05) among the genotypes. FA 02 contained the most minerals; except Zn and Fe, while zinc and iron were found to be highest in genotype FA 01 and FA 06 respectively. FA 01 had a relatively lower amount of minerals. Mg, K, Mn and Cu values in the genotypes were found to be comparable to the values as reported by Hakala et al. (2003) and Tahvonen (1993). Mg, Mn, Zn and Cu

Table 2 Proximate nutrients, vitamin C and carotenoids composition in the strawberry genotypes. Strawberry genotype

Moisture

Protein

Total fat

Percent FA01 FA02 FA03 FA06 LSD value*

91.77 ± 2.62B 92.17 ± 2.93A 92.19 ± 1.57A 90.58 ± 2.75B 1.330

Ash

Dietary fibre

Total sugar

Carbohydrate

g/100 g edible portion 0.53 ± 0.15D 1.17 ± 0.08A 0.62 ± 0.19B 0.57 ± 0.09C 0.020

0.36 ± 0.09B 0.48 ± 0.07A 0.36 ± 0.05B 0.33 ± 0.08C 0.020

0.56 ± 0.09D 0.81 ± 0.17A 0.61 ± 0.12C 0.66 ± 0.14B 0.010

Values were expressed in Means ± SD. Letters in superscript indicate the statistical differences among the genotypes. * DMRT at 5% level of probability.

2.36 ± 0.15B 2.42 ± 0.29A 2.43 ± 0.29A 2.24 ± 0.47C 0.157

3.77 ± 0.25C 6.96 ± 0.71A 4.45 ± 0.33B 4.53 ± 0.51A 0.090

4.647 A 2.137 C 3.317 B 4.730 A 0.8286

Vitamin C

Carotenoids

mg/100 g edible

(lg/100 gm edible

32.24 ± 2.30C 34.45 ± 2.90B 26.46 ± 1.31D 37.77 ± 2.72A 0.060

1.06 ± 0.15C 3.30 ± 0.51A 0.96 ± 0.17C 1.44 ± 0.21C 0.180

1.764 ± 0.025A 2.667 ± 0.178A 2.333 ± 0.227A 2.633 ± 0.187A 0.268

Copper

0.046 ± 0.005A 0.113 ± 0.011A 0.065 ± 0.002A 0.043 ± 0.003A 0.006

Zinc Manganese

0.440 ± 0.022A 0.433 ± 0.022A 0.323 ± 0.018A 0.420 ± 0.019A 0.063

Phosphorous

4. Conclusion The present study reveals that the strawberry genotype grown and developed at the Sher-e-Bangla Agricultural University horticultural farm were rich in vitamin C along with many minerals, particularly the microminerals. Their nutritional value is comparable with or higher than grape and other local fruits. Thus, these strawberries could be a promising dietary supplement to address the needs of vitamin C and micromineral in the local region, particularly amongst children who do not like local fruits, but love the colourful strawberries.

References

Values were expressed in Means ± SD. Letters in superscript indicate the statistical differences among the genotypes. * DMRT at 5% level of probability.

Potassium Sodium

FA01 FA02 FA03 FA06 LSD value*

81.600 ± 0.255B 85.433 ± 0.216A 81.367 ± 0.227B 72.267 ± 3.336C 0.812

Magnesium

17.633 ± 0.356C 23.39 ± 0.072A 19.610 ± 0.258B 17.583 ± 0.256C 0.006

Calcium

7.633 ± 0.216A 9.567 ± 0.178A 9.322 ± 0.293A 8.956 ± 0.098A 0.006

Strawberry genotype

Table 3 Mineral contents in different strawberry genotypes (mg per 100 g edible portion of fruit).

651

levels were consistent with those reported by Recamales et al. (2007) and Giampieri et al. (2012). However, in some of the genotypes, concentrations of the minerals were much higher than those reported for other varieties of strawberry, cherry or mulberry (Mahmood et al., 2012; Recamales et al., 2007), and some values were less than those stated by Giampieri et al. (2012). The strawberry genotypes also contain comparable amounts of minerals as documented in minor fruits grown in Bangladesh (Shajib et al., 2013). Further, compared to grape or local guava or ethnic rhosko (Islam et al., 2010, 2012), the strawberry genotypes contain much more minerals, particularly Mn, Cu, Zn and Fe. Thus, strawberry could potentially be a good source of micro-minerals.

205.647 ± 1.233B 312.467 ± 0.389A 206.267 ± 0.976B 185.967 ± 1.564C 0.089

0.453 ± 0.014A 1.600 ± 0.187A 1.233 ± 0.178a 0.727 ± 0.018A 0.006

0.340 ± 0.022A 0.230 ± 0.021A 0.267 ± 0.014A 0.330 ± 0.025A 0.006

Iron

A. Hossain et al. / Food Chemistry 199 (2016) 648–652

AOAC (1998a). Official method of analysis 930.04: Air-oven method. In S. Williams (Ed.), Association of official analytical chemists (16th ed., Vol. 1, Chapter 3, p. 1). Maryland, USA: Publication by AOAC International. AOAC (1998b). Official method of analysis 978.04: Micro-Kjeldahl method. In S. Williams (Ed.), Association of official analytical chemists (16th ed., Vol. 1, Chapter 3, p. 24). Maryland, USA: Publication by AOAC International. AOAC (1998c). Official method of analysis 983.23: Fat in foods. In S. Williams (Ed.), Association of official analytical chemists (16th ed., Vol. 2, Chapter 45, pp. 45– 64). Maryland, USA: Publication by AOAC International. AOAC (1998d). Official method of analysis 940.26: Ash of fruits. In S. Williams (Ed.), Association of official analytical chemists (16th ed., Vol. 2, Chapter 37, p. 7). Maryland, USA: Publication by AOAC International. AOAC (1998e). Official method of analysis 923.09: Total sugar. In S. Williams (Ed.), Association of official analytical chemists (16th ed., Vol. 2, Chapter 44, pp. 8–9). Maryland, USA: Publication by AOAC International. AOAC (1998f). Official method of analysis: 984.26: Vitamin C (Total) in food. In S. Williams (Ed.), Association of official analytical chemists (16th ed., Vol. 2, Chapter 45, p. 10). Maryland, USA: Publication by AOAC International. BSS (2014). Strawberry farming gains momentum in Rajshahi. . February 2, 2014. Crespo, P., Bordonaba, J. G., Terry, L. A., & Carlen, C. (2010). Characterisation of major taste and health-related compounds of four strawberry genotypes grown at different Swiss production sites. Food Chemistry, 122, 16–24. Emdad, A., Baten, M. A., Hossan, M. I., & Hossain, A. (2013). Characterization and yield potential of strawberry genotypes. Journal of Experimental Bioscience, 4(2), 19–22. Food and Agriculture Organization (FAO) (1998). Vitamin and mineral requirements in human nutrition: Report of a joint FAO/WHO expert consultation (2nd ed.). Bangkok, Thailand. Giampieri, F., Tulipani, S., Alvarez-Suarez, J. M., Quiles, J. L., Mezzetti, B., & Battino, M. (2012). The strawberry: Composition, nutritional quality, and impact on human health. Nutrition, 28, 9–19. Gomez, K. A., & Gomez, A. A. (1984). Statistical procedure for agricultural research (2nd ed.). New York: John Willy and Sons, p. 680. Hakala, M., Lapveteläinen, A., Huopalathi, R., Kallio, H., & Tahvonen, R. (2003). Effects of varieties and cultivation conditions on the composition of strawberries. Journal of Food Composition and Analysis, 16, 67–80. Hossain, I. (2010). . August 21, 2010. Islam, S. N., Khan, M. N. I., & Akhtaruzzaman, M. (2010). A food composition database for Bangladesh with special reference to selected ethnic foods. . Islam, S. N., Khan, M. N. I., & Akhtaruzzaman, M. (2012). Food composition tables and database for Bangladesh with special reference to selected ethnic foods. Edited by Md. Nazrul Islam Khan, Sheikh Nazrul Islam; Reviewed by Sagarmay Barua, INFS, DU; Palal Prokashoni, Shahbag, Dhaka, Bangladesh.

652

A. Hossain et al. / Food Chemistry 199 (2016) 648–652

Islam, M. S., Hossan, M. J., Ahsan, M. K., Mehraj, H., & Jamal Uddin, A. F. M. (2013). Evaluation of growth and yield of for strawberry (Fragaria ananassa) genotypes. The Agricultrists, 11(2), 104–108. Johnsen, S. P., Overvad, K., Stripp, C., Tjonneland, A., Husted, S. E., & Sorensen, H. T. (2003). Intake of fruit and vegetables and the risk of ischaemic stroke in a cohort of Danish men and woman. American Journal of Clinical Nutrition, 78, 57–64. Mahmood, T., Anwar, F., Iqbal, T., Ahmad, I., Bhatti, I. A., & Ashraf, M. (2012). Mineral composition of strawberry, mulberry and cherry fruits at different ripening stages as analyzed by inductively coupled plasma-optical emission spectroscopy. Journal of Plant Nutrition, 35(111–122), 2012. Marinova, D., & Ribarova, F. (2007). HPLC determination of carotenoids in Bulgarian berries. Journal of Food Composition and Analysis, 20, 370–374. Mondal, D. (2010). Possibility of strawberry cultivation in Bangladesh: An assignment on strawberry. . March 30, 2010. Petersen, L. (2002). Analysis of plant materials. In Analytical methods soil, water, plant material, fertilizer. Soil resources management and analytical services. Soil Resource Development Institute, Danida, Camp Sax.

Raghuramulu, N., Madhavan, N. K., & Kalyanasundaram, S. (2003). A manual of laboratory techniques. Hyderabad, India: National Institute of Nutrition, Indian Council of Medical Research, pp. 56–58. Recamales, A. F., Medina, J. L., & Hernanz, D. (2007). Physicochemical characteristics and mineral content of strawberries grown in soil and soilless system. Journal of Food Quality, 30, 837–853. Rodrizues-Amaya, D. B., & Kimura, M. (2004). HarvestPlus handbook for carotenoid analysis. Harvest plus technical monograph series 2. Washington DC and California: IFRI and CIAT. Shajib, M. T. I., Miah, M. N., Begum, P., Kawser, M., Bhattacharjee, L., Hossain, A., ... Islam, S. N. (2013). Nutritional composition of minor indigenous fruits: Cheapest nutritional source for the rural people of Bangladesh. Food Chemistry, 140, 466–470. Tahvonen, R. (1993). Contents of selected elements in some fruits, berries and vegetables on the Finnish market in 1987–1989. Journal of Food Composition and Analysis, 6, 75–86. Vauzour, D., Vafeiadou, K., Pendeiro, C., Corona, G., & Spenser, J. P. E. (2010). The inhibitory effects of berry-derivated flavonoids against neurodegenerative processes. Journal of Berry Research, 1, 45–52.