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ABSTRACT
Calcium lactate (CaL^sub 2^) crystal formation on the surface of cheese continues to be a widespread problem for the cheese industry despite decades of research. To prevent those crystals from forming, it is necessary to keep the concentration of CaL^sub 2^ below saturation level. The limited data available on the solubility of CaL^sub 2^ at conditions appropriate for the storage of cheese are often conflicting. In this work, the solubility of L(+)-CaL^sub 2^ in water was evaluated at 4, 10, and 24°C, and the effects of salt and pH at those temperatures were investigated. The effects of additional calcium and lactate ions on solubility also were studied. The results suggested that temperature and the concentration of lactate ions are the main factors influencing the solubility of CaL^sub 2^, with the other parameters having limited effect.
(Keywords: solubility, calcium lactate, crystallization, Cheddar cheese)
Abbreviation key: CaL^sub 2^ = calcium lactate, NaL = sodium lactate.
INTRODUCTION
For the past several decades, numerous studies have been conducted to identify why crystal appears on cheese and to find ways to prevent them. The previous studies mainly focused on the effects of milk composition and the processing conditions for Cheddar cheese manufacturing on crystal formation. The results of these studies have shown that factors such as a high lactose concentration in milk (Pearce et al., 1973), an increase in numbers of nonstarter bacteria during ripening (Johnson et al., 1990a), storing cheeses at a lower temperature that initially were held at a higher temperature (Pearce et al., 1973), and loose packaging (Johnson et al., 1990b) promote crystal formation. However, the continuing problems with calcium lactate crystals show the need for a better understanding of the process of crystal formation.
Calcium lactate is not a native component of milk; therefore it is necessary to have sufficient amounts of both calcium and lactate ions to form crystals. Once calcium and lactate concentrations exceed the solubility limit at a certain temperature, a thermodynamic driving force for crystallization exists and crystallization might occur. The presence of nucleation sites, such as rough surfaces and cracks, will accelerate crystal formation. Additionally, differences in milk composition and the cheese manufacturing, packaging, and handling procedures might affect calcium availability and lactate synthesis and, hence, crystal formation...