Soluble Protein Content Assessment in Dry Pet Food Raw Materials: Comparison between Fresh Meat and Meat Meal Formulations

Long shelf life and ease of use make dry pet food a popular choice among pet owners, inasmuch as it represents the majority of pet food on the market today. Two kinds of raw materials are commonly employed for the production of dry pet food, namely fresh meats (FMs) and particularly meat meals (MMs). These raw materials, before coming onto the market as dry pet food, undergo production processes, transportation, and, when it comes to MMs, industrial transformations, which may result in unwanted modifications of such ingredients, especially as far as their protein content is concerned. The goal of this study is to analyze the protein content of the raw materials regularly used in the production of dry pet food. Different formulations of white, red, and fish FMs and MMs have been prepared and analyzed. The protein concentration of both FM and MM mixes was assessed by the Bradford assay, with the aim being to evaluate the soluble protein content, which represent also a convenient digestibility index. Subsequently, the quality of proteins was evaluated through the characterization of the electrophoretic profile assessed by SDS-PAGE followed by staining with Coomassie Blue dye. The results proved that the formulations made of FMs, compared to the ones based on MMs, have a higher soluble protein content and a better-defined protein profile, thus making the former the best choice as raw materials for dry pet food production.