KKU Res. J.

2013; 18(3) 371

KKU Res. J. 2013; 18(3): 371-379

http : //resjournal.kku.ac.th

Production of hard tofu from calcium fortified soybean milk and

its chemical and sensory properties
Sunee Eadmusik1*, Prapasri Puwastien2 and Anadi Nitithamyong2
1
Department of Agro-industrail Technology and Management, Faculty of Agro-industry, King Mongkut’s University of Technology North
Bangkok, Prachinburi campus, Prachinburi 25230, Thailand
2
Institute of Nutrition, Mahidol University, Phutthamonthon 4, Nakorn Pathom 73170, Thailand
* Correspondent author: suneee@kmutnb.ac.th

Abstract
Hard tofu, a product from soybean milk, is one of the common food products in Asia. Soybean milk
with soybean to water ratio varying from 1:6 to 1:8 was prepared in triplicate. The weight of soybean used in
all experiments was 200 g. Calcium salt used to fortify soybean milk was 120 mg Ca/100 ml together with
sequestering and stabilizing agents. Calcium-fortified hard tofu was produced by coagulation of the calcium-fortified
soybean milk with saturated MgSO4. Nutritive values and bioaccessibility of calcium in calcium-fortified tofu
were determined. The yields of total solid and protein in calcium-fortified tofu prepared from soybean milk with
a soybean to water ratio of 1:6 were the lowest (78.9+5.4 and 33.0+1.6 g, respectively). In contrast, the highest
yields of both parameters (total solid, 90.5 +3.8 g and protein, 45.4+4.2 g) were obtained in tofu prepared from
soybean milk with the ratio of 1:8. The tofu also contained the highest amount of total calcium (1947+54 mg).
As a result, the soybean to water ratio of 1:8 was selected to be used for calcium-fortified tofu production with
and without adding of sequestering and stabilizing agents. The yield of total solid in the calcium-fortified tofu of
both types was in the same range. However, the total protein yield of tofu with additives was significantly higher
than that without the additives, 45.4+4.2 g compared to 37.0+1.8 g, respectively. Carrageenan, used as stabilizing
agent in preparation of the fortified tofu, may play an important role in holding water and protein, resulted in
higher tofu yield with higher protein content. The addition of the sequestering and stabilizing agents did not show
any significant effects on the total amount of calcium in the calcium-fortified tofu. The calcium fortified tofu was
well accepted, however, its calcium bioaccessibility was lower than that of milk powder which is likely due to
the presence of phytate.

Keywords: Calcium-fortification, Hard tofu, Soybean milk

372 KKU Res. J. 2013; 18(3)

1. Introduction 2. Materials and method

Calcium plays important roles in human Soybean seeds, Chiangmai-60 variety, were
body. Adequate calcium intake prevents osteoporosis purchased from Chiangmai province in the northern
and reduces the risk of hypertension (1). The Thai part of Thailand. They were kept in a cold room at 7-80C
Recommended Daily Intake (Thai RDI), based on until used and were allowed to reach room temperature
2,000 kcal intake for adults and children at 6 or more before tofu processing.
years of age, is 800 mg/day (2). The survey of food and Food grade coagulant (MgSO4.7H2O) was
nutritional status conducted by the Ministry of Public provided by Vidhyasom Co., Ltd. Bangkok, Thailand.
Health in 1995 revealed that Thai people did not have Food grade calcium salt (tri-calcium phosphate) and
adequate calcium intake, the average calcium intake was sequestering agent (potassium citrate) were obtained
344 mg/person/day. from Tinnakorn Chemical and Supply Co., Ltd.,
Soybean, whole dry seed, contains 343 mg Thailand. Stabilizing agent (carrageenan) was obtained
Ca/100g (3). Based on the amount of calcium per from Wang Chemicals Co., Ltd., Thailand.
serving (30 g) which is about 13% Thai RDI, it can be The Central-Healthy Electric Food Grinder
considered as a good source of calcium. Soybean can be (Central Industrial Supply, Co., Ltd., Bangkok, Thailand)
processed into many food products such as soybean milk, was used as a grinder to extract soybean milk and the
tofu, fermented soybean, tempeh, soy sauce, soybean residue was automatically separated.
oil (4, 5). However, soybean milk has been recognised 2.1 Preparation of calcium-fortified soybean
to contain much lower calcium than cow’s milk (20-30 milk
mg/100 ml compared to 120 mg/100 ml, respectively). In Calcium-fortified soybean milk containing 120
2000, Chaiwanon et. al. (6) developed calcium-fortified mg Ca/100 ml was prepared according to Chaiwanon
soybean milk with good calcium bioaccessibility and et al. (6), with the proportion of soybean:water varying
sensory acceptability. Soybean curd or tofu is a high from 1:6 to 1:8 (w/v). Three individual sets of each
protein product widely consumed in Asian countries formula were prepared using an initial amount of 200
and among vegetarians. It is generally made by protein g soybean seeds. The volume of the prepared soybean
coagulation of heated soybean milk with a coagulant, milk, their total solid, protein and calcium content were
followed by moulding and pressing the curd to drain determined, and their yields (amount of components per
the whey (5, 7). Calcium-fortified tofu could provide total volume of heat-treated calcium-fortified soybean
another choice of calcium source to the consumers. milk) were calculated.
Therefore, this research is aimed to produce hard tofu 2.2 Preparation of hard tofu from calcium-
from calcium-fortified soybean milk and to evaluate its fortified soybean milk
chemical and sensory properties. High calcium hard tofu was prepared by
coagulation of the heat-treated calcium-fortified soybean
milk with saturated magnesium sulphate. The proportion
of saturated MgSO4 to soybean seeds was 10 ml to 100 g.
While mixing, saturated MgSO4 was added little by little
KKU Res. J. 2013; 18(3) 373

into calcium-fortified soybean milk until clear separation Sensory evaluation (general appearance, odor,
of soy protein curd from whey appeared. The coagulated taste, texture and overall liking) was conducted with 50
soy protein was immediately transferred into the panelists to determine the liking of calcium-fortified
wooden mould, size 8.5 cm x 8.5 cm x 4 cm, lined with tofu. The panelists were faculty staffs and graduate
muslin-cloth. Then the cloth was folded over the top of students of the Institute of Nutrition, Mahidol University
bean curd. The whey was drained off naturally for 3-5 (INMU) who have been familiar with tofu. Tests on odor,
min and the curd was evenly pressed by placing a 4.5 kg taste, texture and overall liking were conducted using a
weight on the 595 cm2 plate (7.5 g/ cm2) on top of the curd nine-point hedonic scale (1 - dislike extremely; 5 - neither
for an hour or until dripping ceased. Three individual sets like nor dislike; 9 - like extremely). Five categories
of tofu from each formula of calcium fortified soybean just-about-right scales, ranging from 1 - much too light/
milk were prepared. Tofu from non-fortified soybean soft, 3 - just about right, 5 - much too dark/hard, were
milk (1:8 soybean to water ratio) prepared by the same used to evaluate sensory characteristics of colour and
method was used as a control. All the tofu were weighed, hardness. All tofu samples were stored overnight in water
and analysed for total solid, protein and calcium content. at 5-7°C and steamed before being served in the form
Their yields and per cent recoveries were calculated. of a cube (1.5 cm x 1.5 cm x 0.5 cm) with soy sauce.
The optimum soybean to water ratio for soybean milk They were coded in three-digit numbers and presented
preparation was identified based on these parameters. in a randomised arrangement.
2.3 Effect of sequestering and stabilizing 2.5 Statistical analysis
agents on tofu quality The data on tofu quality and sensory
The optimum proportion of soybean to water properties are given as Mean + S.D. Any significant
ratio obtained from the above experiment was used to difference in the tofu quality due to the difference in the
prepare calcium-fortified tofu. Three individual sets soybean to water ratio of the soybean milk was evaluated
of tofu were prepared with and without adding of using SPSS v.9. Kruskal-Wallis H test type. Mann-
sequestering and stabilizing agents in the soybean milk, Whitney U test was used to do pair wise comparison
Yields and per cent recoveries of total solid, protein to indicate any soybean to water ratios which showed
and calcium in the prepared calcium-fortified tofu were significant difference in the tofu quality. It was also used
compared. to evaluate the sensory properties of the prepared tofu
2.4 Chemical and sensory evaluation (non-fortified and calcium-fortified tofu). The significant
The Official Methods of Analysis of AOAC difference was established at p-value < 0.05.
International (8) were used for the determination of total
solid, crude protein, calcium, phosphorus and phytate in
calcium-fortified soybean milk and tofu. Two types of
3. Results and discussion
calcium-fortified tofu, prepared from calcium-fortified 3.1 Effects of soybean to water ratio on the
soybean milk (with and without adding sequestering quality of prepared calcium-fortified tofu
and stabilizing agents), were investigated for calcium There are many factors involved in the quality
bioaccessibility following the simulated gastrointestinal of soybean milk which affect the quality of tofu, i.e.,
digestion procedure of Miller et. al. (9). Dry milk powder soybean variety, type of soybean seeds (whole or split),
and non-fortified tofu were used as control samples. coagulant (types and concentration), soybean to water
374 KKU Res. J. 2013; 18(3)

ratio (7, 10-15). Soybean seeds, Chiangmai-60, have 1947+54 mg. Per cent recovery of total solid (82+9% to
been widely used in Thailand for making soybean 85+6%), protein (84+3 to 100+9%) and calcium (103+7
products. The whole seeds were used in order to get the to 107+8%) in the prepared calcium-fortified tofu were
better soybean milk quality in terms of freshness, flavour, not significantly affected by varying of the soybean to
and extractability of protein (10). Soybean milk is the water ratios except that of protein from 1:6 soybean to
initial product affecting the tofu quality. The effects of water ratio. This implied that the amount of the coagulant
using different soybean to water ratios to prepare calcium (saturated MgSO 4) was sufficient to completely
fortified soybean milk on the extracted total solid and precipitate protein from various calcium-fortified
protein were then evaluated. soybean milk and all calcium in the calcium fortified
As shown in Table 1, the calcium-fortified soybean milk was incorporated into the tofu curd along
tofu produced from 1:8 soybean milk gave the highest with the protein.
total solid and protein yields (90.5+3.8 and 45.4+4.2 g, According to the high yields and recoveries of
respectively), whereas that produced from 1:6 soybean total solid, protein and calcium of the tofu prepared from
milk gave the lowest yields (78.9+5.4 and 33.0+1.6 g, soybean to water ratio of 1:8 (Table 1), it was selected
respectively). Total calcium yield in the calcium-fortified to be used for studying the effect of sequestering and
tofu prepared from various formulas of soybean milk stabilizing agents on tofu quality.
were significantly different, ranged from 1559+40 to
Table 1. Yield of total solid, protein and calcium and their per cent recoveries (Mean + SD.) in calcium-fortified
tofu prepared from different soybean to water ratios
Total solid Protein Calcium
Soybean :
%
Water Yield (g) % Recovery Yield (g) Yield (mg) % Recovery
Recovery
1:6 78.9 + 5.4b 83 + 3 33.0 + 1.6 84 + 3b 1559 + 40c 107 + 8
1:7 85.0 + 8.0ab 82 + 9 43.3 + 0.6 100 + 6a 1705 + 61b 103 + 7
1:8 90.5 + 3.8a 85 + 6 45.4 + 4.2 100 + 9a 1947 + 54a 104 + 3
Significant * ns ns * * ns
a,b
Mean values showing different superscript letter differ significantly (p<0.05)
ns = not statistically significant

3.2 Effect of sequestering and stabilizing closer to the hard tofu purchased from the market than
agents in calcium-fortified soybean milk on tofu Tofu-A. Although total solid yields (about 90 g) and
quality their recoveries (about 85%) in two types of tofu were
The quality of calcium-fortified tofu not different, the Tofu-NA had lower protein yield and its
prepared from soybean milk with (Tofu-A) and without recovery than Tofu-A (37.4+1.7 g compared to 45.4+4.2 g
(Tofu-NA) sequestering and stabilizing agents are and 87+6% compared to 100+9%, respectively). In
shown in Table 2. The appearance of Tofu-NA was addition, the derived Tofu-NA had slightly lower in
KKU Res. J. 2013; 18(3) 375

total weight than Tofu-A (298+10 and 364+14 g/ 200 g during heating of soybean milk fortified with some
initial soybean seeds, respectively). It was likely that forms of calcium salt, i.e. calcium lactogluconate (17).
carrageenan which was used as a stabilizing agent in It was found to extend the stability of calcium salt in
calcium-fortified soybean milk plays an important role calcium-fortified soybean milk (6). However, in
in holding water and protein in the derived tofu. Being this study, there was no effect of using sequestering
a sulphated polysaccharide, carrageenan can exist as a and stabilizing agents on calcium recovery in
negatively charged polymer over a wide range of pH calcium-fortified tofu. The amount of total calcium
and can form complexes with protein in the presence and its per cent recovery in calcium-fortified tofu with
and absence of calcium ions (16). Above the isoelectric and without adding the agents were not significantly
point, which was the pH of soybean milk mixture (pH different.
about 6.2) during tofu production, polyvalent metal such Although the use of additives provided a
as Ca2+ can form bridges between the negative charged slightly higher yield and per cent recovery of protein in
carboxyl groups of the protein and the sulphate groups of the calcium-fortified tofu, it did not significantly affect
the polysaccharide (carrageenan). The extensive network those parameters of total solid and calcium. Furthermore,
structure formed by carrageenan could trap more water the tofu without additives was more similar in appearance
in the interstitial spaces of the gel (16), resulted in the to commercial tofu found in the market. Therefore, it was
higher protein yield and slightly higher weight in the possible to omit the use of additives in order to reduce
calcium-fortified tofu with adding the agents than that the cost and avoid the complexity of this processing step.
without the agents. Tofu without additives was then selected for sensory
Potassium citrate was normally used as evaluation.
a sequestering agent to protect protein coagulation

Table 2. Yield of total solid, protein and calcium and their per cent recoveries (Mean + SD.) in calcium-fortified
tofu with and without adding sequestering and stabilizing agents
Soybean : Total solid Protein Calcium
Water1 Yield (g) % Recovery Yield (g) % Recovery Yield (mg) % Recovery
1:8A 90.5 + 3.8 85 + 6 45.4 + 4.2 a 100 + 9 1947 + 54 104 + 3
1 : 8 NA 88.9 + 3.2 86 + 6 37.4 + 1.7 b
87 + 6 1901 + 180 100 + 7
Significant ns ns * ns ns ns
1
tofu was prepared from calcium-fortified soybean milk with (A) or without (NA) adding agents
a,b
Mean values showing different superscript letter differ significantly (p<0.05)
ns not statistically significant
3.3 Chemical and sensory properties of tofu, with and without adding sequestering and stabilizing
calcium-fortified tofu agents, and their in vitro calcium bioaccessibility are
Total solid, crude protein, calcium, phosphorus, presented in Table 3. Calcium content in 100 g of
phytate content in non-fortified and calcium-fortified non-fortified and calcium-fortified tofu with and without
376 KKU Res. J. 2013; 18(3)

the additives were 62, 518 and 693 mg, respectively. calcium phosphorus ratio of 1:1.2, compared to 1:9.4
Calcium fortification provided higher content of of non-fortified tofu. Similar level of phytate content
phosphorus in the derived tofu because the tri-calcium was found in non-fortified and calcium-fortified tofu,
phosphate fortificant was used, resulting in the better 530 and 516 mg/100 g, respectively.

Table 3. Nutritive values of tofu and calcium-fortified tofu1

Nutritive values Calcium-fortified tofu
Unfortified tofu
per 100 g With agents Without agents
Total solid, g 28.3 24.8 32.2
Protein (total N x 5.71), g 15.4 12.4 14.4
Lipid, g 9 NA 9
Calcium, mg 62 518 693
Phosphorus, mg 580 NA 815
Ca:P ratio 1:9.4 NA 1:1.2
Phytate, mg 530 NA 516
Ca dialysability2, % 14 13 11
Calcium dialysability of dry milk powder = 26%, based on 25 mg Ca
= 24%, based on 250 mg Ca
1
tofu prepared from soybean to water ratio of 1:8
2
based on tofu with 7 g protein
NA not analyzed

The calcium bioaccessibility (based on the prepared tofu (contained more than 500 mg phytate/100
amount of one serving tofu which contained 7 g protein g tofu). This is because phytate is the hexaphosphate
and 290-330 mg Ca) of calcium-fortified tofu with ester of inositol, the stereologic conformation of its
additives was 13% compared to 11% of that without highly polar compound reveals its high affinity toward
additives and 14% of non-fortified tofu. These values di- and tri-valent cations, such as copper, iron, zinc and
were much lower than those of dry milk powder, 26% calcium (20).
at 25 mg Ca and 24% at 250 mg Ca. The finding was in For the effect of additives, potassium citrate
accordance with those reported for soy-based formula has been used as a sequestering agent. This is because
(11.4%) by Miller et al. (cited by 18) and for cooked of its chelating property - citric ions in the molecule
soybean seeds (11.1%) by Kamchan et al. (19). High can chelate with calcium, thus forming a chain
phytate, naturally present in the protein complex of structure. The adjacent chains of cation-citrate complex
soybean, is believed to be the main factor involving are linked by extensive hydrogen bonding through
in the low bioaccessibility of calcium in both types of water molecule (21). However, the effect of potassium
KKU Res. J. 2013; 18(3) 377

citrate on calcium bioaccessibility has not been reported. overall liking scores which represent the liking degree
Carrageenan was used as the stabilizing agent in calcium of all sensory characteristics of both prepared tofu were
fortified soybean milk for tofu production. At the pH of about 6, which means “like slightly”. The liking scores
the soybean milk during tofu production (about 6.2), of taste and texture were also about 6. Scores of odor
Ca2+ can form bridges between the negatively charged were in the range of “like slightly to like moderately”
carboxyl groups of the protein and the sulphate groups (6.3, 6.4 and 6.9 for control tofu, non-fortified tofu
of the polysaccharide of carrageenan. The presence of and calcium fortified tofu, respectively). The prepared
carrageenan in calcium-fortified soybean products was tofu showed significant difference in liking scores of
reported to reduce calcium bioaccessibility (22, 23). hardness. The hardness score of control and non-fortified
The effect of each sequestering and stabilizing agent on tofu (3.0 and 3.2, respectively) was just-about-right.
calcium bioavailability should be investigated. Although the appearance of calcium-fortified Tofu-NA
The sensory liking scores of non-fortified and was closer to the hard tofu in the market, its hardness
calcium fortified tofu without adding sequestering and score from sensory evaluation was significantly higher
stabilizing agents are presented in Table 4. Commercial than the non-fortified tofu. The higher total solid content
tofu was used as a control sample. Control and non-fortified found in the prepared Tofu-NA (32.2 g compared to 28.3
tofu showed similar characteristics, except hardness, g of non-fortified tofu) is likely to be reflected in the
to those of calcium-fortified tofu. General appearance harder texture. Other sensory characteristics were not
scores of the prepared tofu before tasting were in the different from the control. However, their overall liking
range of “like slightly”, with the average score of 6.5. The scores were the same, about 6 (like slightly).

Table 4. Sensory liking scores1 (Mean + SD., n=50) of non-fortified tofu and calcium fortified tofu
Tofu3
Sensory Characteristics Significant
Control Non-fortified Ca-fortified
Before taste Appearance 6.3±1.3 6.5±1.2 6.6±1.1 ns
Colour2 3.3±0.7 3.0±0.4 2.9±0.4 ns
After taste Overall liking 6.6±1.3 6.4±1.4 6.3±1.7 ns
Odor 6.3±1.7 6.4±1.4 6.9±1.4 ns
Taste 6.7±1.3 6.4±1.5 6.2±1.6 ns
Texture 6.6±1.3 6.3±1.4 5.9±1.8 ns
Hardness2 3.0±0.5a 3.2±0.7a 3.6±0.9b *
a,b
Mean values showing different superscript letter differ significantly different (p<0.05)
ns not statistically significant
1
nine-point hedonic scale ranging from dislike extremely, 1; neither like nor dislike, 5; like extremely, 9.
2
five categories Just About Right scale ranging from much too light / soft, 1; just about right, 3; much too dark or hard, 5.
3
non-fortified tofu purchased from a local market (control) and prepared from soybean to water ratio of 1:8 (non-
fortified); calcium fortified tofu was prepared without adding agents
378 KKU Res. J. 2013; 18(3)

4. Conclusion (2) The Ministry of Public Health. Department

of Health: Nutrition Division. The Dietary
Various soybean to water ratios used to prepare Reference Intake. 2003. Thai.
calcium fortified soybean milk did not considerably (3) Puwastien P, Raroengwichit M, Sungpuag P,
affect the derived tofu quality. The soybean to Judprasong K. Thai Food Composition Tables.
water ratio of 1:8 was the optimum proportion for Nakorn Pathom: Institute of Nutrition Mahidol
calcium-fortified soybean milk to produce tofu. Not University (INMU);1999. Thai.
including thesequestering and stabilizing agents in the (4) Golbitz P. Traditional soyfoods: Processing and
calcium-fortified soybean milk did not affect the yield products. Am Ins Nutr. 1995: S570-2.
and recovery of total solid and calcium in the prepared (5) Liu K. Soybeans as functional foods and
tofu. However, it produced tofu with slightly lower total ingredients. Illinois: AOCS Press; 2004.
weight and protein yield. The derived calcium-fortified (6) Chaiwanon P, Puwastien P, Nitithamyong A,
tofu contained calcium about 10 times higher than that Sirichakwal PP. Calcium fortification in soybean
of non-fortified tofu. Its calcium bioaccessibility was milk and in vitro bioavailability. J Food Comp
lower than that of dry milk powder (24-26%) due to the and Anal. 2000;13(3): 19-27.
presence of high phytate. The sensory liking score of (7) Cai T, Chang KC. Processing effect on soybean
calcium-fortified tofu without additives was not different storage proteins and their relationship with tofu
from that of non-fortified tofu and tofu purchased from quality. J Agric Food Chem. 1999;47: 720-7.
the market. Their liking scores were “like slightly”. The (8) AOAC. Official methods of analytical chemistry
calcium-fortified tofu obtained from this research could (16 th ed.). Arlington: The Association of Official
be a new choice of calcium source to consumers and Analytical Chemists, Inc. 1995.
could decrease a calcium deficiency problem in Thailand. (9) Miller DD, Schricker BR, Rasmussen RR,
Campen DV. An in vitro method for estimation
5. Acknowledgements of iron availability from meals. Am J Clin Nutr.
1981;34: 2248-56.
The authors would like to thank the Tinnakorn (10) Hou HJ, Chang SKC. Yield and quality of soft
Chemical and Supply Co., Ltd. and Wang Chemicals tofu as affected by soybean physical damage and
Co., Ltd. for chemical support. storage. J Agri Food Chem. 1998;46: 4798-805.
(11) Lim BT, DeMan JM, DeMan L, Buzzell RI.
Yield and quality of tofu as affected by soybean
6. References and soymilk characteristics: Calcium sulfate
(1) Weaver CM, Heaney RP. Calcium. In: Shils ME, coagulation. J Food Sci. 1990;55: 1088-90.
Shike M, Ross AC, Caballero B, Cousins RJ, (12) Sun N, Breene WM. Calcium sulfate concentration
editors. Modern nutrition in health and disease. influence on yield and quality of tofu from five
9th ed. Baltimore: Lippincott William and soybean varieties. J Food Sci. 1991;56: 1604-7.
Wilkins; 2006. p. 194-210. (13) Beddows CG, Wong J. Optimization of yield and
properties of silken tofu from soybean. I. The
KKU Res. J. 2013; 18(3) 379

water : bean ratio. Int J Food Sci Tech. 1987;22: (18) Shen LH, Luten J, Robberecht H, Bindels J,
15-21. Deelstra H. Modification of an in vitro method
(14) Bhardwej HL, Bhagsari AS, Joshi JM, Rangappa for estimating the bioavailability of zinc and
M, Sapra VT, Rao MSSS. Yield and quality of calcium from foods. Z Lebensm Unters Forsch.
soymilk and tofu made from soybean genotypes 1994;199: 442-5.
grown at four locations. Crop Sci. 1999;39: (19) Kamchan A, Puwastien P, Sirichakwal PP,
401-5. Kongkachuichai R. In vitro calcium bioavailability
(15) Poysa V, Woodrow L. Stability of soybean seed of vegetables, legumes and seeds. J Food Comp
composition and its effect on soymilk and tofu and Anal. 2004;17: 311-20.
yield and quality. Food Res Int. 2002;35: 337-45. (20) Weaver, C.M., & Kannan S. Phytate and mineral
(16) Karim AA, Sulebele GA, Azhar ME, Ping CY. bioavailability. In: Reddy NR, Sathe SK, editors.
Effect of carrageenan on yield and properties of Food Phytates. Florida: CRC Press; 2002.
tofu. Food Chem. 1999;66: 159-65. (21) Wong WD. Mechanism and theory in food
(17) Yazici F, Alvarez VB, Mangino ME, Hansen chemistry. New York: Van Nostrand Reinhold,
PT. Formulation and processing of a heat 1989.
stable calcium-fortified soy milk. J Food Chem. (22) James WT, Branch WJ, Southgate DT. Calcium
1997;62(3):535-8. binding by dietary fiber. Lancet. 1978;1: 638-9.
(23) Harmuth-Hoene AS, Schelenz R. Effect of dietary
fiber on mineral absorption in growing rats. J
Nutr. 1980;110: 1774-84.