Optimization of parameters for adding low- and high-methoxylated pectins to curd mass for geroprotective purposes

Pectins are considered to have geroprotective properties through enterosorption, antioxidant activity and stabilization of milk structure. The aim of the study is to scientifically substantiate the optimal pH, amount and stages of addition of low-methoxylated and high-methoxylated pectin to the curd mass in order to achieve the maximum moisture retention capacity, the lowest syneresis value and improved structural and mechanical properties. The addition of low-methoxylated and high-methoxylated pectin separately and in combination at amounts of 0.25–1.5% was studied at pH 3.0–6.0. In addition, a pH test was carried out in the range of 4.1–4.5 for combined addition. Moisture retention capacity, syneresis, hardness and cohesiveness, and viscosity were evaluated. The uniformity of pectin distribution was controlled by the methylene blue dye method and the Ca-pectate method, and the distribution was recognized as uniform in all samples. The experiments were carried out three times and statistical processing was performed using ANOVA post-hoc with Tukey's criterion (p<0.05). The optimal pH for high-methoxylated pectin was 3.5, for low-methoxylated pectin – 4.6. Within a very narrow pH range of 4.3, the syneresis value was the highest at a 50:50 ratio. The optimal amount of each pectin was 1.0%. Addition at the initial stage (to freshly prepared curd from cow's milk) is effective for both types of pectin, but for combined addition, a method was proposed: adding low-methoxylated pectin to freshly prepared curd, and high-methoxylated pectin to the finished curd mass. At pH 4.3, the 50:50 pectin ratio provided the maximum moisture retention capacity (78.0%), the minimum syneresis (3.2% on the initial day, 8.0% after 14 days) and a hardness of 0.67 N. Compared to the control experiment value of 2.9 mmol/kg, the lipid peroxidation value after 14 days was 1.6 mmol/kg (which is below the oxidation threshold for dairy products of ≤4 mmol/kg). Recommended parameters: total pectin concentration 1.0% (0.5% low-methoxylated pectin + 0.5% high-methoxylated pectin), pH 4.3, addition of low-methoxylated pectin at the initial stage, and high-methoxylated pectin at the final stage. The finished curd mass had improved geroprotective and structural-mechanical characteristics.