Effects of composition and preparation condition of fortified milk on absorption and bioavailability of calcium in rats

Calcium is an important mineral especially for the elderly. The average intake of calcium by the elderly women is below the reference nutrient intake (RNI). The amount of calcium absorption and calcium bioavailability in menopausal women is low. Therefore, the main aim of this research was to evaluate the effect of fortification and preparation condition on the absorption and bioavailability of calcium in milk powder formulas applied for ovariectomized (OVX) and OVX-osteoporosis (OS) rats. (1) skim milk powder (T1), (2) skim milk powder fortified with calcium carbonate (1300 mg), inulin (10 g), eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) (1.1 g), vitamins D3 (10 μg), B6 (1.5 mg) and K1 (55 μg) (T2) and (3) skim milk fortified with calcium citrate (1300 mg), inulin (10 g), EPA + DHA (1.1g), vitamins D3 (10 μg), B6 (1.5 mg) and K1 (55 μg) (T3) were formulated based on the North American and Western European dietary allowances. The ingredients were blended using high speed mixer for 5 minutes. The basal and fortified formulas were fed to OVX and OVX-OS rats and the plasma calcium, feces calcium, bone calcium content, bone breaking strength (maximum load), and bone morphology were measured to evaluate calcium absorption and bioavailability. The effect of particle size on absorption and bioavailability of calcium on OVX and OVX-OS rats was studied. Optimization on cycle and pressure of high-pressure homogenizer was done to produce T2-nano and T3-nano. In vivo study of calcium absorption and bioavailability in OVX and OVX-OS rats demonstrated that calcium fortification increased absorption and bioavailability. Calcium absorption and bioavailability showed a significant (p < 0.05) increase using T2 and T3 compared with T1 in OVX rats. Absorption and bioavailability of calcium from T2 were higher than T3 in OVX rats. The calcium absorption and bioavailability of T2-nano (absorption: 89.06% and bioavailability: 41.65%) and T3-nano (absorption: 80.22% and bioavailability: 34.82%) increased significantly (p < 0.05) compared with T2 (absorption: 63.54 % and bioavailability: 24.64%) and T3 (absorption: 33.66% and bioavailability: 15.94%) in OVX rats. T2-nano could enhance the calcium absorption and bioavailability better than T3-nano in OVX rats. The best milk powder for OVX rats was T2-nano with the positive effect of size reduction on absorption and bioavailability of calcium. It was observed that T2 and T3, in OVX-OS rats, had higher calcium absorption and bioavailability than T1. The calcium absorption and bioavailability were improved with consumption of T2 compared with T3 in OVX-OS rats. The results provided that absorption and bioavailability of calcium in OVX-OS rats increased with consumption of T2-nano (absorption: 82.09% and bioavailability: 30.17%) and T3-nano (absorption: 68.67% and bioavailability: 20.38%) compared with T2 (absorption: 60.54% and bioavailability: 9.74%) and T3 (absorption: 42.87% and bioavailability: 4.23%). T2-nano in OVX-OS rats had more positive effect on absorption and bioavailability of calcium than T3-nano. The best milk powder for OVX-OS rats was T2-nano with the positive effect of size reduction on calcium absorption and bioavailability. The current study revealed that OVX rats exhibited higher calcium bioavailability and absorption than OVX-OS rats. In conclusion, this study had successfully developed as a safe and effective fortified milk powder because the basal diet and compounds composed of fully natural food grade components eligible for food application. They were added under limited dosage. The formula could increase calcium absorption and bioavailability and decrease bone loss in OVX and OVX-OS rats as a model of menopause and menopause-OS women.

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