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INGREDIENTS
45
The global market for bone health foods is now worth US$2.5Bn, and is expected to grow at
over 4% per annum1. Here DR. GERHARD GERSTNER, technical service manager special salts
for Jungbunzlauer Ladenburg GmbH, discusses important technological as well as economical
aspects of calcium fortification in dairy products with a focus on micronised tricalcium citrate
DAIRY PRODUCTS:
the calcium
challenge
CALCIUM: A HOT TOPIC
Fighting osteoporosis and promoting calcium intake
is a hot topic right now in Europe. At the International Osteoporosis Foundation conference in December 2001, Health and Consumer Protection
Commissioner David Byrne emphasised his intention
to take action at EU level 2.
‘Osteoporosis is a disease that is sadly overlooked,
under-diagnosed and under-treated. This silent epidemic affects millions of Europeans, causing human
suffering and taking a heavy economic toll,’ he said.
One in three woman and one in eight men over the
age of 50 are affected by an enhanced bone fragility and an increased fracture risk.
During the conference, experts agreed to further increase efforts such as optimising diagnostics and treatment and promoting adequate intake of calcium and
vitamin D in the diet.
Looking at the ingredients list of dairy products, it
is evident that there is not a single source of calcium
but rather a range of different possibilities which can
be used commercially:
■ inorganic salts like calcium chloride, calcium carbonate and calcium phosphate;
■ milk minerals comprised mainly of calcium phosphate;
■ organic salts like tricalcium citrate, calcium lactate,
calcium lactate gluconate and calcium gluconate.
The selection of the appropriate calcium source for
a specific application is usually based on the consideration of a number of properties associated with the
respective product such as solubility, calcium content,
taste and bioavailability. Economic considerations are
another important factor.
Calcium joins a range of
ingredients that add value to
dairy products
presents . . .
A
s everybody knows that dairy
products usually contain substantial
amounts of calcium, they have been and
still are an ideal food to be fortified with extra calcium
to meet nutritional needs by providing larger amounts
in one single serving.
However, the feasibility of calcium addition has to
be considered as technologically milk products represent a complex food matrix. This challenge drives
mineral salt suppliers such as Jungbunzlauer to offer
a range of different calcium salts to be able to tune
them to food manufacturers’ applications: tricalcium
citrate, calcium gluconate and the new product development calcium lactate gluconate.
SOLUBILITY VS. CALCIUM CONTENT
When fortifying liquid milk products, solubility, dissolution characteristics and stability of ingredients in
solution are a major issue. There are calcium salts 䊳
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46
FIG. 1: SOLUBILITY OF JUNGBUNZLAUER TRICALCIUM CITRATE IN WATER
Solubility TCC (g/L)
2,0
1,5
1,0
30˚ C
60˚ C
90˚ C
0,5
0,0
4
5
6
7
8
9
pH
䊴 with good solubility like calcium gluconate, calcium lactate, and calcium lactate gluconate but their
drawback is a comparably low calcium content (913% calcium). The inorganic calcium chloride (36%
calcium) displays good solubility, but its use is restricted due to its bitter and salty taste. Other inorganic calcium salts with a high calcium content like
calcium carbonate and calcium phosphate (38-40%
calcium), on the other hand, are poorly soluble.
Tricalcium citrate offers a good combination: The
commonly used tetrahydrate form shows a high calcium level (21%) and moderate solubility (0.9 g/L).
Tricalcium citrate shows improved solubility at pHvalues below 4.5 as found in fruit preparations used
for fruity milk products. Contrary to other salts, tricalcium citrate is better soluble at low temperatures
which can be an advantage for cold food processing
(Fig 1).
To further increase the solubility and ease of dispersion, Jungbunzlauer has developed a particularly
fine (micronized) tricalcium citrate grade. With this
special granulation of min. 90% < 20 µm, it can be
suspended in milk or whey drinks and high concentrations of calcium (eg, 1.6 g Ca/L) can be reached
without negative taste effects.
TASTE AND MOUTHFEEL
Generally, high levels of calcium, particularly insoluble forms like carbonates and phosphates, tend to
produce a chalky mouthfeel and may promote astringency or bitter taste in the finished product. Calcium
lactate may impart some bitter notes at high concentrations, comparable to characteristics found for calcium chloride3 .
Calcium carbonate may come across as soapy or
lemony. Calcium phosphate has a bland flavour, but
imparts a gritty mouthfeel. Negative effects of calcium on taste can be masked with chelating agents (eg
SPECIAL REPRINT FROM INTERNATIONAL FOOD INGREDIENTS NO. 3 2002
tripotassium citrate), and the use of stabilisers (e.g.
carrageenan) as well as with the addition of flavourings. Tricalcium citrate is a very neutral tasting salt as
masking agents are not necessary.
It is known that using highly soluble calcium salts
at high concentrations may lead to adverse effects in
dairy applications4,5. The addition of mineral salts and
especially of calcium has a strong impact on functionality of milk products during processing and when
consumed. Due to the fact that with higher soluble
salts more free calcium ions are in solution and available for reaction than with lower soluble ones, complications in the form of calcium sediments can develop with time or when the product is heated during
manufacturing or in the household. This is the case,
if the natural milk components caseinate and phosphate react with available calcium.
Thus, although it might be easier to add highly soluble calcium salts rather than tricalcium citrate to
milk products, higher amounts of calcium might be
difficult to achieve without control of pH and addition of chelating agents such as potassium citrate 4,5.
Since the particle size and solubility are linked with
mouthfeel properties, Jungbunzlauer has developed
micronized grades for tricalcium citrate combining
excellent dispersion characteristics with a neutral taste
profile.
BIOAVAILABILITY
Any nutrient’s effectiveness depends on its bioavailability, which means how well the human body absorbs and utilises it. On average, only about 10 to
30 % of calcium is absorbed from a mixed diet by
healthy adults6 . Several different factors influence this
level, among which the type of salt which provides the
calcium. Various scientific studies have shown that organic calcium salts outperform inorganic calcium
sources such as calcium carbonate and calcium phosphate with regard to their relative bioavailability. Tricalcium citrate, calcium gluconate and calcium lactate
gluconate all belong to the highly-bioavailable organic
sources, as shown by extensive human and animal
studies4..
ECONOMIC CONSIDERATIONS VS.
CALCIUM CONTENT
Although inorganic calcium salts are cheaper than organic ones due to their low price and high calcium
content, they are not used in fortified milk products
to a large extent. Comparing the mainly used organic
sources on the other hand, they are all in the same
price range, except for the premium calcium sources
calcium lactate gluconate and the milk minerals.
For this reason, the wide range of calcium contents
of calcium gluconate (9%), calcium lactate (13%) and
tricalcium citrate (21%) has a considerable impact on
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FIG. 2: MAKING OF MILK DRINK, CREAM CHEESE PREPARATION AND DESSERT FORTIFIED WITH MICRONISED TRICALCIUM CITRATE
Cream cheese, sugar
Low fat milk, buttermilk, whey product,
sugar, fruit juices, glucose syrup, flavour
+Tricalcium Citrate M 2090
Low fat milk, cream, sugar,
cocoa powder, flavour
+Tricalcium Citrate M 2090
+Tricalcium Citrate
M 7090
Cold stirring
Cold stirring
Cold stirring
Fruit
preparation
Stabiliser
carrageenan
Thickening
agents
Pasteurising
Pasteurising
Pasteurising
Fortified milk drink:
20% calcium RDI in 100 ml
Fortified cream cheese preparation:
16% calcium RDI in 100 g
Fortified dessert:
15% calcium RDI in 100 g
the raw material cost when the price of calcium added
is calculated for the product to be fortified. Among
the organic salts with high bioavailability and more
neutral taste profiles, tricalcium citrate (21% calcium)
clearly stands out as the most economic option for calcium addition and is the main choice for milk products.
APPLICATIONS
The described characteristics of micronised tricalcium
citrate makes it an ideal calcium salt for all kinds of
applications of calcium-fortified dairy products. Some
relevant examples are given below. By adding extra
calcium, these products can be fortified to higher levels or simply readjusted to the calcium levels of milk
where processing (e.g. in cottage cheese) or addition
of ingredients with low/no calcium (eg cocoa, fruits,
sugar) lead to a decrease of calcium content.
To achieve a stable suspension in liquid milk products within seconds, a jet mixer (e.g. Ytron-Y, Ytron
Germany) can be used at 50°C. This temperature is
recommended for mixing to avoid damage to the fat
matrix of the milk. With conventional stirrers, homogeneous dispersion of tricalcium citrate will take
longer, but can be done at cold temperatures (6-8°C).
FORTIFICATION OF YOGHURTS
Plain yoghurt contains 120mg calcium per 100g
(15% calcium Recommended Daily Intake, RDI),
which is equivalent to the level of milk. Addition of
highly soluble calcium salts (calcium gluconate, calcium lactate) prior to fermentation had been studied
by American and Turkish researchers7-9. Several negative effects had been found, such as lack of heat stability of the calcium-fortified milk blend to be used
for inoculation and negative consequences on the fermentation period and on sensory scores.
For fortification of yoghurt, lower soluble forms of
calcium have advantages, if they do not impart a gritty
mouthfeel. Ultra-fine Tricalcium Citrate M 2090 can
be added prior pasteurisation of the milk. After inoculation and incubation, the resulting plain yoghurt
contains eg, 200mg calcium/100 g (25 % calcium
RDI) without significant negative consequences on
firmness or syneresis.
This fortified plain yoghurt can be used as such or
also as a suitable intermediate product in order to
maintain a high calcium level in the final yoghurt
even after ingredients low in calcium (such as fruits)
had been added.
FORTIFICATION OF MILK DRINKS
AND DESSERTS
Fortification of these products with tricalcium citrate
is not a difficult task (Fig 2). The ultra-fine Tricalcium Citrate M 2090 can be added with the other
dry ingredients, e.g. via a Venturi blender to the product stream, usually at cold temperatures (6-8°C).
There is no particular sequence to be followed, however ingredients increasing viscosity such as thickening agents are added preferably at the end directly before pasteurisation.
FORTIFICATION OF CREAM CHEESE PRODUCTS
If fruits are used for cream cheese or also for yoghurt
products, an indirect addition of tricalcium citrate to
the milk product via the fruit preparation might be
the optimum solution (Fig 2). Fruit preparations generally have a low pH and high citric acid/fruit acid
concentration which has a positive effect on solubility
and dispersibility of tricalcium citrate.
In this application it is therefore possible to use Tricalcium Citrate M 7090 which is also a micronised
grade, but with a less strict particle size limit (min. 90
% < 70 µm) compared to M 2090 (max. 90% > 20
µm). Besides the fortification aspect, tricalcium 䊳
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48
HEALTHY
INFORMATION
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䊴
citrate has also a positive stabilising influence in the
fruit preparation. Calcium pectinate bridges are built
up and improve the firmness of the fruit texture.
FORTIFICATION OF COTTAGE CHEESE
Cottage cheese usually contains 60 mg/100 g of
calcium in the creamed form and only 32 mg/100 g
in the dry curd form compared to 120mg calcium in
milk. However, cottage cheese is popular as a low-fat
and high quality protein food. To increase the nutritional value, calcium salts can be added to the curd
right after setting as demonstrated in studies done at
Ohio State University 10. Calcium levels of up to
200mg/100g could be reached, but the overall quality was inferior to the control.
Recent studies about calcium as well as fibre and inulin enrichment of cottage cheese had been done at
Arla Foods, Sweden11. Jungbunzlauer tricalcium citrate M 2090 had been selected because of its neutral
taste properties in this application.
The technologists’ aim was to reach at least 15% of
the Swedish calcium RDI (120 mg of 800 mg) in 100
g of a creamed cottage cheese. In this case, calcium
was not added to the curd process, but to the dressing which is mixed with the curds at the end.
Tricalcium citrate M 2090 was added to a mixture
of skimmed milk, cream and salt which was stirred at
8°C for 15 min total. The fortified milk was then
heated to 50°C and inulin + citrus fibres added at
lower stirring rate. Finally, the mixture was homogenised and pasteurised. At the end, this dressing
with extra calcium was added to the curds to obtain
the fortified cottage cheese product.
To assess the influence of processing on taste properties and final calcium content in the dressing, parameters such as fat content (0.3 vs. 9 % w/w), homogenising pressure (20 vs. 120 bar), and inulin concentration (0.5 vs. 3,4 % w/w) had been varied. Good
results with 16 % calcium RDI in 100 g could be obtained at high fat content, high pressure and low inulin content. Optimum results (17 % RDI) were
found at high fat content, high pressure, and high inulin concentration.
Taste panel tests revealed that the fortified creamed
cottage cheese did not show off flavours with calcium
concentrations of 17 % RDI. As addition of inulin increases absorption of calcium significantly, this ‘bifunctional’ food can serve as an even better source to
fight calcium deficiency.
CONCLUSIONS
Consumers increasingly prefer food with added nutritional value rather than taking nutritional supplements to fill up their calcium needs. Dairy products
are seen to be one of the best means to help fighting
calcium deficiency as they are known to be a substan-
SPECIAL REPRINT FROM INTERNATIONAL FOOD INGREDIENTS NO. 3 2002
tial source of this important mineral. By adding extra
calcium in the form of organic calcium salts, dairy
products can be fortified to higher levels and provide
individuals who choose not to consume large
amounts of dairy products to meet their daily requirements in one or two servings.
Calcium salts are also used to simply readjust the
product to the calcium levels of milk where processing or addition of low-calcium ingredients lead to a
decrease of calcium contents. Combined functional
foods, such as food where prebiotic fibres and calcium had been added are seen to be the next step in
calcium fortification which further optimises calcium
intake, exploiting the synergistic effect between e.g. inulin and calcium on calcium absorption.
The challenge for milk products manufacturers is to
provide a product having high calcium content with
good taste and appealing properties.
Since micronised tricalcium citrate is available, it
has replaced inorganic as well as organic salts in existing dairy applications. An important explanation
from the technological standpoint is that especially in
the milk matrix, a highly dispersible calcium salt has
advantages over highly soluble alternatives.
REFERENCES
1. Leatherhead Food International, UK, Press Release
No. 827 (2002)
2. EU Press Release Memo/01/416, Brussels, 12/2001
3. Tordoff, M.G. Some basic physophysics of calcium
salt solutions. Chemical Senses 21, 417-424 (1996)
4. Flynn, A.; Cashman, K. Calcium. In: Hurrel, R.
(ed.) The Mineral Fortification of Foods, Leatherhead
Food International, UK, (1999)
5. Reddy, S.; Sher, A.; Van Vadehra, D.; Wredal,
E.R. Calcium complex and a process of making a food
fortified with calcium. US Patent 5,928,691 (1999)
6. National Research Council. Calcium, In: Recommended Dietary Allowances: 10th edition. Washington
D.C.; National Academy Press, 174-184 (1989)
7. Fligner, K.; Lindamoood, J.B.; Hansen, P.M.T.
Fortification of low-fat plain yogurt with calcium gluconate. Cultured Dairy Products J. 23, 5-9 (1988)
8. Yousef, A.E.; Rusli, M. Modification of starter culture for production of calcium fortified yogurt. Cultured
Dairy Products Journal 30, 20-25 (1995)
9. Pirkul, T.; Temiz, A.; Erdem, Y.K. Fortification of
yoghurt with calcium salts and its effect on starter microorganisms and yoghurt quality. Int. Dairy J. 7, 547552 (1997)
10. Martin, J.H.; Zullo, P.A. Methods for increasing
calcium in cottage cheese. Cultured Dairy Products J.
26, 11-18 (1991)
11. Sabine Remling and Eva Ekman, Arla Foods Sweden and Chalmers University of Technology, Sweden,
IFI
personal communication (2002)