Nutrient and Maillard reaction product concentrations of commercially available pet foods and treats

Abstract

Thermal processing is used to produce most commercial pet foods and treats to improve safety, shelf life, nutritional characteristics, texture, and nutrient digestibility. However, heat treatments can degrade protein quality by damaging essential amino acids, as well as contribute to the Maillard reaction. The Maillard reaction forms melanoidins that favorably improve food qualities (e.g., color, flavor, aroma), but also form Maillard reaction products (MRP) and advanced glycation end-products that may negatively affect health. Because commercial pet diets are frequently fed to domestic cats and dogs throughout their lifetimes, it is critical to quantify MRP concentrations and understand the variables that influence their formation so future diets may be formulated with that in mind. Because few research studies on MRP in pet diets have been conducted, the goals of this study were to measure the MRP in commercial pet foods and treats, estimate pet MRP intake, and correlate MRP with dietary macronutrient concentrations. Fifty-three dry and wet dog foods, dog treats, and cat foods were analyzed for dry matter, organic matter, crude protein, acid-hydrolyzed fat, total dietary fiber, and gross energy using standard techniques. MRP were analyzed using high-performance liquid chromatography and gas chromatography-mass spectrometry. Data were analyzed using the Mixed Models procedure of SAS 9.4. Dry foods had lower reactive lysine concentrations and reactive lysine: total lysine ratios (indicator of damage) than wet foods. Wet foods had more fructoselysine (FRUC) than dry foods; however, dry dog treats contained more FRUC than wet dog treats. The greatest 5-hydroxymethyl-2-furfural (HMF) concentrations were measured in dry and wet dog foods, whereas the lowest HMF concentrations were measured in dry and wet cat foods. Based on dietary concentrations and estimated food intakes, dogs and cats fed wet foods are more likely to consume higher carboxymethyllysine and FRUC concentrations than those fed dry foods. However, dogs fed wet foods are more likely to consume higher HMF concentrations than those fed dry foods. In cats, those fed dry foods would consume higher HMF concentrations than those fed wet foods. We demonstrated that pet foods and treats contain highly variable MRP concentrations and depend on diet/treat type. In general, higher MRP concentrations were measured in wet pet foods and dry treats. While these findings are valuable, in vivo testing is needed to determine if and how MRP consumption affect pet health.

Keywords: advanced glycation end-products; pet food processing; pet nutrition.

Figure 1.

Lysine, furosine, and Maillard reaction product (MRP) concentrations (dry matter basis) of commercially available pet foods and treats. ^u−zMeans with different superscripts within a row differ by Wilcoxon’s test (P < 0.05). Error bars are standard errors of the means. TMRP, total Maillard reaction products; CML, carboxymethyllysine; HMF, 5-hydroxymethyl-2-furfural.

Figure 2.

Estimated daily intake (mg/kg BW^0.75) of Maillard reaction products of commercially available pet foods and treats. ^a–cMeans with different superscripts within a row differ by Tukey’s test (P < 0.05). ^u–zMeans with different superscripts within a row differ by Wilcoxon’s test (P < 0.05). Error bars are standard errors of the means. TMRP, total Maillard reaction products; CML, carboxymethyllysine; FRUC, fructoselysine; HMF, 5-hydroxymethyl-2-furfural.

Figure 3.

Heatmap of correlation values (r) between nutrients and Maillard reaction products of commercially available pet foods and treats. The following correlations tended to be significant (P < 0.10): FRUC-NFE (P = 0.0519), FURO-NFE (P = 0.0519), FRUC-CP (P = 0.0626), FURO-CP (P = 0.0626), and CML-TDF (P = 0.0577). NFE, nitrogen-free extract; CP, crude protein; AHF, acid-hydrolyzed fat; TIF, total insoluble fiber; TDF, total dietary fiber; TSF, total soluble fiber; TMRP, total Maillard reaction products; CML, carboxymethyllysine; FRUC, fructoselysine; FURO, Furosine; HMF, 5-hydroxymethyl-2-furfural.