Chemical and nutritive characteristics of canola meal from Canadian processing facilities☆
Introduction
Canola is one of the most important oilseed crops in Canada and its processing for oil is an important part of the overall canola industry in Canada (Unger, 2011, Canola Council of Canada, 2015). Canola meal (CM), which is a co-product of the canola oil extraction process accounts for approximately 60% of the whole canola seed and is in most cases produced by pre-press solvent extraction with hexane. The pre-press solvent extraction process of canola requires a number of steps, each involving a wide range of temperature, moisture and time. All these conditions contribute to variations in the chemical composition and nutritional value of CM. For example, in the cooker, the temperature ranges from 85 to 95 °C, the moisture ranges from 4.5 to 6.0% and cooking lasts for 30–40 min. In the desolventizer/toaster (DT), the temperature ranges from 95 to 115 °C, and the process may last for 35–50 min (Unger, 2011, Canola Council of Canada, 2015). Studies have shown that excessive heating during pre-press solvent extraction may result in reduced concentration of amino acids (AA) particularly lysine. This is because Maillard reactions may occur between amino acids and reducing sugars as a result of the combination of heat and moisture applied to the meal in the DT (Nursten, 2005). Earlier research from our laboratory (Slominski, 1997) showed a profound effect of moist heat treatment on CM quality. Application of temperatures higher than 110 °C resulted in a significant increase in neutral detergent insoluble crude protein (NDICP) and dietary fiber contents and a significant decline in protein digestibility. Another study by Almeida et al. (2014) showed that autoclaving of CM at 103 °C for 20, 30 and 45 min increased NDF and acid detergent insoluble N and reduced the standardized ileal amino acids digestibility when fed to growing pigs. No study has been conducted to determine the effect of processing practises or conditions in the various processing facilities on the chemical compositions and information of Maillard reaction products in CM from Canadian processing facilities. Canola meal end-users desire increased meal consistency and more information on the nutritive value and heat damage of amino acids in CM (Spragg and Mailer, 2007). Therefore, the objectives of this study were: 1) To determine the effect of processing conditions on the chemical compositions and indicators of protein damage (Maillard reaction products including dietary fiber, NDICP, and lignin with associated polyphenols) in CM from Canadian processing facilities, 2) To determine the variations in the chemical composition of CM produced in Canada over time, and 3) To develop prediction equations for determining the components that can be used as indicators of heat damage including lysine, dietary fiber, NDICP, and lignin with associated polyphenols.
Section snippets
Canola meal sample collection and preparation
In years 2011, 2012, 2013, and 2014 CM samples were collected from 11 canola processing facilities in Canada which included: Bunge Oilseed Processing at Altona, MB; Harrowby, MB; Nipawin, SK; Fort Saskatchewan, SK and Hamilton, ON; Archer Daniels Midland (ADM) Agri-Industries Ltd. at Windsor, ON; Lloydminster, SK and Yorkton, SK; James Richardson International (JRI) Canola Oil Processing Plant at Yorkton, SK and Lethbridge, AB; Cargil Canola Processing, Clavet, SK. In each year, 3 samples were
Effect of processing facility and year on the chemical and nutritive composition of CM
As presented in Table 1, there were variations (P < 0.05) between processing facilities in the contents of CP (402–429 g/kg DM), ether extracts (26.0–43.0 g/kg DM), ash (71.0–79.0 g/kg DM), and total P (10.6–11.6 g/kg DM). However, there were no facility differences in phytate and non-phytate P contents. Canola meal from Facilities 1, 4 and 10 had similar and highest CP contents while those from Facilities 7 and 11 were significantly lower (P < 0.05) in CP than Facilities 1, 4 and 10. The overall mean
Discussion
The pre-press solvent extraction of canola meal consists of 10 basic stages which are: 1) Cleaning and drying of the seed to approximately 6% moisture, 2) Preconditioning (heating) to prevent shattering of the seeds during flaking, 3) Flaking by passing through a roller mill, 4) Cooking to deactivate myrosinase enzyme and to reduce oil viscosity and thereby coalesce the oil, 5) Expelling to reduce the oil content to approximately 15–20%, 6) Solvent extraction with hexane to remove additional
Conclusions
There were variations between processing facilities and years in the contents of CP, NDF, ether extract, total phosphorus, simple sugars, oligosaccharides, total dietary fiber, glucosinolates, NDICP, lignin and polyphenols and lysine of CM produced in Canada. The high total dietary fiber with the corresponding high NDICP and low glucosinolates with the corresponding low lysine observed in the CM from some processing facilities could have been caused by meal overheating and the consequent
Conflict of interest
The authors declare that they have no competing interests.
Acknowledgements
The authors wish to acknowledge the Canola Council of Canada and Agriculture and Agri-Food Canada for funding this project.
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Presented, in part, at the Poultry Science Association Meeting 2014, Corpus Christi, Texas and at the 14th International Rapeseed Congress 2015, Saskatoon, Saskatchewan, Canada.