Introduction: Flaxseed and oats are recognized for offering numerous health benefits, being sources of minerals, vitamins, and dietary fiber. According to Brazilian legislation, bulk food is defined as any food that is measured and packaged in the presence of the consumer. Proper storage of these products is of vital importance, as they are perishable and subject to quality variations due to chemical, enzymatic, or microbiological deterioration.

Objective: This study aimed to analyze the moisture content and titratable acidity of oat and flaxseed flours sold in bulk in the city of Macaé-RJ, Brazil.

Methodology: Oat and flaxseed flour samples sold in bulk were collected from the main natural product stores in Macaé-RJ (Stores A, B, and C). Moisture analysis was performed using an infrared moisture analyzer, and titratable acidity was determined according to the methodology described by the Adolfo Lutz Institute (1985).

Results: None of the samples showed moisture values above 15%, as established by Brazilian legislation (RDC No. 711, July 2022). The oat flour samples from Stores A, B, and C presented moisture contents of 10.27%, 11.54%, and 11.29%, respectively. The flaxseed flour samples showed lower moisture values compared to the oat flour: 5.57%, 6.08%, and 6.47% for Stores A, B, and C, respectively.

Regarding acidity, there is no specific Brazilian regulation for this parameter; however, it was observed that the samples showed low titratable acidity. The flaxseed flour from Store A had the highest acidity (5.79%), followed by Stores B (2.615%) and C (0.845%). For oat flour, Store C showed the highest acidity (1.71%), followed by Stores B (0.745%) and A (0.375%).

Conclusion: It can be concluded that both oat and flaxseed flours exhibited results indicating good preservation conditions.