The effects of a range of barrel dry heat temperatures (20 to 180 oC), and moist heat pressure (MHP) (120 oC 15 min 192 kPa) on general nutritional, protein solubility, and in vitro protein degradability characteristics of canola meal were investigated. Increasing dry heat temperature was negatively correlated with meal crude protein (CP), soluble CP, neutral detergent fibre, acid detergent insoluble CP, and rapidly degradable (B1 Fraction) protein; and positively with NPN, intermediately degradable (B2 Fraction) protein, dry matter, lipid, carbohydrate, and in vitro rumen-undegradable protein. Relative to control meal, MHP increased in vitro rumen-undegradable protein, and in vitro CP digestibility; and decreased soluble protein, and 0.5% KOH solubility. Positive increases of Fraction A and B2, as B1 decreased, suggest barrel temperature induces protein hydrolysis and conversion of rapidly to intermediately degraded protein, respectively. The changes observed may have a great effect on ruminal degradation and supply of protein and AA for ruminant utilisation.

Initially, samples of Australian canola, soybean, cottonseed and flaxseed meal produced by solvent-extraction, expeller and cold-press technologies collected from late 2014 to early 2015 were analysed for general chemical composition, protein and ruminal digestibility characteristics. The oilseed meals had levels of ash, neutral-detergent insoluble crude protein, total intestinal digested protein, B1, B2, B3 and C protein content similar to those in previous reports, but lower Fraction A (non-protein N) levels than in previous reports. Acid-detergent insoluble fibre, metabolisable energy, total digestible nutrients, ash (P < 0.05), neutral-detergent fibre, in vitro dry matter digestibility, crude protein (CP), true protein, acid-detergent insoluble CP, soluble protein, in vitro rumen-undegradable protein (RUP), total tract digested protein, Fraction A, B2 and C (P < 0.01) differed among oilseed types. Dry matter, the ratio of RUP to total tract digested protein (P < 0.05), CP, lipid, soluble protein, RUP, Fraction A, B1 and B2 (P < 0.01) differed among oil-extraction techniques. Utilising an in vitro simulated rumen proteolysis procedure by Krishnamoorthy et al. (1983), mean ranges of in vitro RUP were greater and varied more so in canola (18.8–70.1%) than soybean (40.3–54.0%), cottonseed (31.5–33.9%) and flaxseed (18.5–21.8%) meals. Estimated RUP was lower (P < 0.01) in cold-press than expeller and solvent-extraction oilseed meals.

The effects of a range of barrel dry heat temperatures (20 to 180 oC), and moist heat pressure (MHP) (120 oC 15 min 192 kPa) on Maillard reaction product (MRP) formation and canola meal structural characteristics were investigated. Increasing dry heat temperature was negatively correlated with meal whiteness L* and yellowness b* (early-MRP) and positively with surface hydrophobicity. Relative to control meal, MHP increased early-MRP, redness, browning index (late-MRP), and acidity; and decreased L*, surface hydrophobicity, b*, and Abs294nm (intermediate-MRP). Dry heat-associated changes in surface hydrophobicity suggest protein unfolding and side-chain modifications. Lack of high MW polypeptides at dry heat temperatures of 160 and 180 oC imply protein denaturation and formation of insoluble polypeptides. Specific dry heat temperatures increased surface lipid and induced the formation of protein matrix and aggregation. Meal surface morphology rounded and flattened at specific dry heat temperatures, and smoothed with MHP. Differences in lipid-related functional groups were evident between dry heat temperatures, and with MHP. Treatment with MHP affected amide I and II, α-helix, β-sheet, their respective ratios and the total protein fingerprint region; fragmented meal into proteolysis-resistant protein aggregates with crevices containing lipid droplets; and, reduced solubility of canola meal polypeptides > 40 kDa. The changes observed may have a great effect on ruminal degradation and supply of protein and AA for ruminant utilisation.

Simple SummaryCanola meal, a by-product of oil production from canola seed, is a source of protein commonly incorporated into dairy and feedlot rations. Processing conditions and pressure treatments can alter the quality of protein in canola meal. In this study, the impact of expeller dry heat and moist heat pressure duration time on general nutritional properties, in vitro protein degradability, Maillard reaction product formation, and molecular and microscopic structural characteristics of canola meal were investigated. Increased dry heat temperature rapidly increased digestible protein and non-protein nitrogen content, and constricted amide II secondary structure. Increased moist heat pressure treatment duration promoted browning, and the conversion of protein to more intermediately and slowly degradable forms. Dry heat and moist heat pressure affected meal protein solubility and protein and lipid-related functional groups. Moist heat pressure fragmented canola meal into enzyme-resistant aggregates with crevices containing oil bodies. Induced changes may impact the supply of protein and amino acids and subsequently the yield and composition (protein and lipid) of milk produced by dairy cows. These findings benefit producers of canola meal by further describing the effects of processing and treatment conditions on protein characteristics, particularly those which affect the production potential of ruminants fed canola meal as a source of protein.AbstractTo improve the protein nutritional quality of canola (Brassica napus L.) meal, further investigation of the effects of processing conditions and post-production treatments is desirable. The impact of barrel dry heat temperature (20 °C (cold press) and 100 °C (expeller)) and moist heat pressure (MHP) duration time on general nutritional properties, Maillard reaction product (MRP) formation, in vitro protein degradability, and molecular and microscopic structural characteristics of canola meals were investigated. Increased MHP duration reduced (p < 0.05) dry matter, soluble protein, rapidly degradable protein, yellowness (early MRP), whiteness (late MRPs), absorbance at 294 nm (intermediate MRPs), and amide I; and increased (p < 0.05) non-protein N, neutral detergent fibre, neutral detergent insoluble crude protein (CP), intermediately and slowly degradable protein, in vitro effective CP degradability, redness, degree of colour change, and browning. Increased dry heat temperature reduced (p < 0.01) CP and rapidly degradable protein, constricted amide II, reduced (p < 0.05) protein solubility in 0.5% KOH and increased (p < 0.05) acid-detergent fibre and intermediate MRPs. Browning index and redness exhibited potential as rapid indicators of effective CP degradability and soluble protein, respectively. Dry heat and MHP altered (p < 0.05) lipid-related functional groups. Dry heat affected napin solubility, and MHP altered cruciferin and napin solubility. Application of MHP induced the formation of proteolysis-resistant protein aggregates with crevices containing oil ...