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Tofu Fortified With Specialty Minerals Precipitated Calcium Carbonate (PCC)

Tofu is a popular source of protein and other nutrients in Asian cuisines, as well as for vegetarians and vegans (who do not eat any animal products). While soybeans have good levels of calcium, the mineral remains behind when the soymilk, from which tofu is made, is extracted. Soymilks have low levels of calcium—only about 10 mg of elemental calcium in 100 ml. During the manufacture of tofu, some calcium can be added from the processing chemicals, depending on what is used as a coagulant system.  

In diets that do not include dairy products or other high-calcium foods, calcium-enriched tofu can be an important source of the vital nutrient.


Fortifying Tofu with Calcium Carbonates
Questions about calcium carbonate’s utility in fortifying tofu—and its effect on both processing and product—were addressed convincingly at a poster session of the 2005 Institute of Food Technologists annual meeting. The Specialty Minerals Inc. (SMI) Healthcare Laboratory presented positive testing results and other supportive data that led to the following conclusions:

  • Calcium carbonate does not inhibit the coagulation of soymilk, from which the tofu is made.
  • Calcium carbonate addition can affect tofu firmness, either positively or negatively, depending on the coagulant system.
  • Rheological measurements correlated well with durometer hardness of the tofu; creep compliance in particular was seen as a good predictor of tofu firmness.
  • In general, small particle-sized precipitated calcium carbonates (PCCs) were the most effective in enhancing tofu firmness and structure. Larger particle-sized precipitated and ground calcium carbonates were less satisfactory.
  • A magnesium chloride (MgCl2) coagulant system is the most compatible with the addition of calcium carbonate to tofu.
  • The coagulant blend of magnesium chloride, calcium sulfate, glucono-delta-lactone (MgCl2 / CaSO4 / GDL) is the most sensitive to calcium carbonate addition.
  • Calcium carbonate addition with reduced GDL levels gives a tofu cake firmness and structure superior to tofu cake with higher GDL level and no calcium carbonate.
  • Calcium carbonate can effectively be used to increase the calcium content of tofu, while providing the benefit of greater firmness.

Specialty Minerals Precipitated Calcium Carbonates (PCCs) For Tofu Fortification
The two calcium carbonate grades which gave the best results in this study were a 0.7 micron prismatic PCC and a 1.9 micron scalenohedral PCC. Both grades have narrow particle-size distributions with uniform particles.

The 0.7 micron PCC used was ViCALity Albafil® PCC. This is a low-lead PCC, with less than 500 ppb (parts per billion) lead, made in the SMI plant in Adams, Massachusetts. An ultra-low-lead version, CalEssence® 70 PCC, has less than 125 ppb lead, and is especially useful in highly fortified products which must comply with California Proposition 65 lead limits. It, too, is made in Adams, Massachusetts.

The 1.9 micron PCC used in the study was ViCALity® Extra Light PCC. It has an open, starburst-like structure. As with all ViCALity® PCCs, it is made in Adams, and contains less than 125 ppb lead. The ultra-low-lead version is CalEssence® 160 PCC. The same size and shape product is made in the SMI plant in Birmingham, U.K. This is Calopake® Extra Light PCC.


Tofu Fortification Study Details
A downloadable set of PowerPoint slides outlines the study, materials, and methods, and gives the detailed results. These include the creep-compliance rheology curves.

Click here to download these details.

 

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