Oxidative stability and nutritional quality of poultry by-product meal: An approach from the raw material to the finished product
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The current study aimed to investigate the relationship between oxidative stability and in vitro digestibility in the rendering process of poultry by-product meal (PBM). One hundred PBM batches were sampled from two integrated rendering plants (n = 50) and two independent rendering plants (n = 50). The parameters related to raw material, processing and finished product (PBM) were considered independent variables. In the PBM samples, the in vitro digestibility of organic matter (IVDOM) and the oxidative stability, measured as induction period (IP) by an oxygen bomb, were determined. These data were considered dependent variables for multivariate statistical analyses. Data from the independent variables were submitted to Exploratory Factorial Analysis (EFA). Subsequently, a hierarchical cluster was performed for the dependent variables. For oxidative stability, the samples were grouped into three clusters according to IP as follows: low (89 ± 12.2 min), medium (127 ± 9.7 min) and high (180 ± 13.3 min) (P = 0.001). Among the principal components (PC), the moisture (P = 0.009) and water activity (P = 0.039) were the factors related to the PBM that most influenced oxidative stability. The moisture content of 25 ± 12.4 g/kg and water activity of 0.24 ± 0.11 resulted in the lowest oxidative stability, indicating that excessive drying leads to less stable PBM. Oxidative stability was also influenced by synthetic antioxidants (P = 0.036). PBM samples were grouped into four clusters based on their in vitro digestibility of organic matter (IVDOM): very low (723 ± 14.6 g/kg), low (759 ± 9.7 g/kg), moderate (803 ± 3.3 g/kg), and high (848 ± 15.8 g/kg). Lower average (101 ± 2.05 °C, P = 0.022) and maximum (106 ± 1.02 °C; P = 0.004) processing temperatures led to higher PBM digestibility. Time to processing and rendering conditions directly affected PBM quality. Better standardization of those factors can favor the production of a nutritionally more suitable ingredient with longer oxidative stability.