Article pubs.acs.org/JAFC
Calcium, Iron, and Zinc Bioaccessibilities of Australian Sweet Lupin (Lupinus angustifolius L.) Cultivars Weeraya Karnpanit,†,‡ Ranil Coorey,§ Jon Clements,∥ Wenika Benjapong,‡ and Vijay Jayasena*,† †
School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, New South Wales 2751, Australia Institute of Nutrition, Mahidol University, 999 Phutthamonthon 4 Road, Salaya, Nakhon Pathom 73170, Thailand § School of Public Health, Faculty of Health Sciences, Curtin University, Bentley, Perth, Western Australia 6102, Australia ∥ Department of Agriculture and Food, Western Australia, 3 Baron-Hay Court, South Perth, Western Australia 6151, Australia ‡
ABSTRACT: In this study, we aimed to determine the effect of the cultivar and dehulling on calcium, iron, and zinc bioaccessibilities of Australian sweet lupin (ASL). Ten ASL cultivars grown in 2011, 2012, and 2013 in Western Australia were used for the study. The bioaccessibilities of calcium, iron, and zinc in whole seed and dehulled lupin samples were determined using a dialysability method. The cultivar had significant effects on calcium, iron, and zinc contents and their bioaccessibilities. Average bioaccessibilities of 6% for calcium, 17% for iron, and 9% for zinc were found for whole seeds. Dehulled ASL had average calcium, iron, and zinc bioaccessibilities of 11%, 21%, and 12%, respectively. Compared to some other pulses, ASL had better iron bioaccessibility and poorer calcium and zinc bioaccessibilities. Dehulling increased calcium bioaccessibilities of almost all lupin cultivars. The effect of dehulling on iron and zinc bioaccessibilities depends on the ASL cultivar. KEYWORDS: bioaccessibility, minerals, Australian sweet lupin, cultivars
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plays a crucial role in mineral deficiency.28,29 The dialysability method is one of the most commonly used in vitro methods to determine bioaccessibility. It is inexpensive, rapid, and highly reproducible.30 This assay has been applied widely as a reliable predictor for assessing mineral bioavailability due to its good correlation with in vivo studies.31 No information on the effect of the cultivar and dehulling on the mineral bioaccessibility of Australian sweet lupin (ASL) has been published. In the present study, we aimed to determine the effect of the ASL cultivar and dehulling on the bioaccessibilities of calcium, iron, and zinc.
INTRODUCTION Lupin is an underutilized grain legume with high protein and dietary fiber contents but low starch content. Australia is the largest lupin producer accounting for approximately 60% of the total world production.1 Lupin has been consumed in the Mediterranean region and the Andean highlands for centuries but not much elsewhere in the world. There is a growing interest in using lupin within the human diet mainly due to its health benefits.2,3 Studies have shown that consumption of lupin-based foods exerts various health benefits, including a blood-pressure-lowering effect, bowel function improvement, a cholesterol-lowering effect, and a glucose-lowering effect.4−7 The fiber and raffinose family oligosaccharides in lupin are considered prebiotics.8,9 Despite these health benefits, lupin is mainly used for livestock feed outside of the Mediterranean region. Lupin has great potential as a future sustainable source of plant protein for human consumption.10,11 Its flour is considered an excellent ingredient for supplementing various food products.12,13 Substitution of wheat flour with lupin flour in traditional wheat-based food products can improve their nutritional quality, such as the protein, dietary fiber, mineral, and bioactive compound contents in these products.14−17 A range of lupin-incorporated foods with good consumer acceptability such as biscuits,12 bread,18−21 instant noodles,17 muffins,22,23 pasta and spaghetti,24 and tofu25 have been developed. Mineral deficiencies are a major global public health problem especially in the developing countries. According to the World Health Organization (WHO),26 around 30% of the world population suffers from iron and/or zinc deficiency. The global prevalence of inadequate calcium intake is over 50%.27 In addition to inadequate intake, poor mineral bioavailability also © 2017 American Chemical Society
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MATERIALS AND METHODS
Plant Material. Lupin seed samples from 10 cultivars (Belara, Corumup, Gungurru, Jenabillup, Mandelup, PBA Barlock, PBA Gunyidi, Quilinock, Tanjil, and Walan 2385) grown in 2011, 2012, and 2013 cultivation years were provided by the Department of Agriculture and Food, Western Australia. Seed samples of the Walan 2385 cultivar were available from only two cultivation years (2012 and 2013). All lupin cultivars were grown at the Wongan Hills research station (30.54°S, 116.43°E) in Western Australia. A 5 kg sample of each ASL cultivar from each cultivation year was obtained. A subsample of 500 g from each ASL sample was used for the study. The whole seeds of ASL were cleaned using a vacuum separator (Kimseed, Perth, Australia) to remove foreign material. Immature and damaged seeds were removed manually. All seed samples were packed in sealed polyethylene bags and stored in a refrigerator at 4 °C until further analysis. Sample Preparation. Whole seeds were dehulled using a dehuller (Amar industries, Punjab, India), and the kernels and hulls were Received: Revised: Accepted: Published: 4722
January 30, 2017 May 14, 2017 May 22, 2017 May 22, 2017 DOI: 10.1021/acs.jafc.7b00445 J. Agric. Food Chem. 2017, 65, 4722−4727
Article
Journal of Agricultural and Food Chemistry Table 1. Calcium, Iron, and Zinc Contents in Whole Seeds of Lupina mineral content (mg/100 g of DM) cultivar
calcium ± ± ± ± ± ± ± ± ± ±
Belara Corumup Gungurru Jenabillup Mandelup PBA Barlock PBA Gunyidi Quilinock Tanjil Walan 2385
296.32 280.66 371.73 253.85 251.49 201.58 245.95 247.40 249.16 277.52
average
267.22 ± 52.24
iron
24.87 b 57.74 b 48.23 a 7.56 bc 26.91 bc 25.30 c 25.00 bc 20.99 bc 28.02 bc 9.56 b
3.92 2.14 2.31 2.57 3.10 2.46 2.75 3.72 2.29 1.81
± ± ± ± ± ± ± ± ± ±
0.38 0.29 0.12 0.30 0.25 0.46 0.16 0.30 0.27 0.37
2.74 ± 0.70
zinc a de cde bc bd b cd a cde e
3.78 4.98 5.09 2.23 2.39 2.74 1.40 3.42 4.13 5.01
± ± ± ± ± ± ± ± ± ±
1.90 0.62 0.52 0.42 0.67 0.39 0.43 0.87 1.51 0.57
abc a a cd bd bd d abc ab a
3.46 ± 1.51
Each value represents the mean ± SD. N = 6 for all cultivars except Walan 2385, for which N = 4. Mean values with different letters in the same column are significantly different (P < 0.05).
a
μg/mL) were prepared to calculate the individual mineral contents. To prevent mineral contamination, all glassware was soaked in 10% HNO3 (v/v) overnight and rinsed with deionized water. Mineral Bioaccessibility. Bioaccessibilities of calcium, iron, and zinc were determined using a dialysability method as previously described.33 To simulate gastric digestion, the lyophilized sample (10 g) was homogenized with 80 g of deionized water, and the pH was adjusted to 2.0 with 6 M HCl. Freshly prepared pepsin solution (3 g) was added, and the mixture was made up to 100 g with deionized water. The mixture was incubated at 37 °C for 2 h in a shaking water bath (SWB20, Ratek) set at 100−120 strokes/min. The gastric digest mixture (20 g) was weighed into a wide-necked 250 mL Erlenmeyer flask. Dialysis tubing containing 25 g of deionized water and NaHCO3 (mole equivalent to NaOH used in the titratable acidity) was placed in the flask. Titratable acidity was defined as the amount of 0.5 M NaOH required to titrate the gastric digest and pancreatin−bile salt mixture to pH 7.5. The amount of NaOH in the titratable acidity was used to calculate the amount of NaHCO3 (mole equivalent) for preparing dialysis tubing. The mixture was incubated at 37 °C for 30 min in the shaking water bath. The pancreatin−bile salt mixture (5 g) was added, and the mixture was incubated at 37 °C for 2 h. After incubation, the dialysis tubing was removed from the flask, washed by deionized water, patted dry on a paper towel, and weighed. The contents of the dialysis tubing were analyzed for mineral contents by flame atomic absorption spectrophotometry. The bioaccessibility of the mineral was calculated as follows: bioaccessibility (%) = D/C × 100, where D is the dialyzed mineral content (μg/g) and C is the total mineral content (μg/g).33 Statistical Analysis. The mean and standard deviation of the mineral content and bioaccessibility of each ASL cultivar represented six values (duplicate values of three cultivation years), except there were four values for Walan 2385. Statistical analyses were conducted using the SPSS statistical analysis software program, version 22 (IBM Corp., Armonk, NY). To determine the effect of the cultivar on the mineral content and bioaccessibility, one-way analysis of variance (ANOVA) with Tukey’s posthoc test was used. A paired sample t test was used to compare mineral bioaccessibilities between whole seeds and dehulled lupin. A P value of 23%). Although higher in iron content, lower iron bioaccessibilities were found in Quilinock and Belara. In dehulled seed samples, Gungurru had the highest iron bioaccessibility (35%) and Belara had lower iron bioaccessibility (
