Technical note: Repeatability and reproducibility of curd yield and composition in a miniaturized coagulation model

Area of Science:

• Dairy Science
• Food Chemistry
• Analytical Chemistry

Background:

• Miniaturized coagulation (MC) models are used for analyzing milk curd yield (CY), cheese microstructure, and texture.
• Uncertainty exists regarding the suitability of MC with small milk volumes (<50 mL) for evaluating CY and chemical composition.
• The potential interference of preservatives in raw milk with the MC process requires investigation.

Purpose of the Study:

• To evaluate the repeatability and reproducibility of CY, curd moisture, and fat and protein content on curd dry matter (DM) using MC with 40 g of milk.
• To assess the impact of preservatives in raw milk on MC results.
• To determine the suitability of MC for routine dairy analysis.

Main Methods:

• Miniaturized coagulations were performed by three operators over three consecutive days using raw milk (RM) and raw milk with preservative (RMP).
• Repeatability of CY was assessed using the relative standard deviation of six miniaturized curds per day.
• Reproducibility was evaluated using the Horwitz ratio, and differences between RM and RMP were analyzed using the z-test.

Main Results:

• Repeatability of CY was below 5% for MC trials with both RM and RMP.
• Good reproducibility was observed for CY from RM, and fair reproducibility for CY from RMP.
• Lower accuracies for curd moisture and fat/protein content on curd DM were noted, particularly with RMP; however, z-tests showed no significant differences between RM and RMP for CY and chemical composition.

Conclusions:

• Preservatives have negligible effects on MC, validating its use with preserved milk.
• MC using 40 g of milk is suitable for evaluating CY and chemical composition, offering extended milk sample stability.
• The method allows for flexible laboratory trial scheduling and broader sample analysis within batches.