Effect of thermal and high-pressure treatments on the antirotaviral activity of human milk fractions

Rotaviral gastroenteritis is associated with high rate of infant mortality and morbidity. Antirotaviral activity has been associated with some glycoproteins, such as immunoglobulins A (IgA), lactoferrin (LF), mucins and lactadherin of human milk. Although holder pasteurization (HoP, 63 degrees C for 30 min) is the treatment currently applied to human milk, it may lead to a decrease of its bioactive properties. The antirotaviral capacity of human milk showed to be mainly associated with the whey fraction, focusing on IgA and LF, with neutralizing values of 100, 100 and 62%, at 1 mg protein/mL, respectively. HoP reduced the antirotaviral activity of human whey, IgA and LF, 30, 98 and 60%, respectively. Interestingly, high temperature-short time (HTST) pasteurization at 75 degrees C for 20 s did not affect the antirotaviral activity of samples, while the highest HHP treatment at 600 MPa for 15 min only reduced the activity of human whey, IgA and LF, 9, 40 and 10%, respectively

Determination of lactadherin concentration in dairy by-products by ELISA: Effect of heat treatment and hydrolysis

Lactadherin is a peripheral glycoprotein of the milk fat globule membrane with several attributed biological activities. In this study, we developed an indirect competitive ELISA to determine lactadherin concentration by using a rabbit polyclonal antiserum. The ELISA was applied to quantify lactadherin in several dairy by-products. Of the products tested, raw and commercial buttermilk had the highest concentrations of lactadherin (6.79 and 5.27 mg/g of product, respectively), followed by commercial butter serum (4.86 mg/g), commercial skim milk (4.84 mg/g), and raw whey (1.20 mg/g). The concentration of immunoreactive lactadherin was also determined in dairy by- products after they were subjected to different technological treatments. Thus, raw products were heat treated at combinations of temperature and time typically used in the dairy industry, and commercial products were hydrolyzed using 3 proteolytic enzyme preparations. Heat treatments of whey and buttermilk resulted in a smaller decrease in lactadherin concentration than did hydrolysis as determined by ELISA and electrophoresis. At high temperatures for long durations, the loss of lactadherin was higher in whey than in buttermilk, with the maximal reduction of around 48% found after treating whey at 72 degrees C for 60 min. Hydrolysis of commercial products with proteolytic enzymes resulted in a marked decrease of immunoreactivity within the first 5 min of treatment, which thereafter was constant throughout 4 h of hydrolysis. These results demonstrate that dairy by- products from milk fat processing are good natural sources of lactadherin, although technological processes have to be considered, because they have different effects on lactadherin content