The Study On Extrusion Pretreatment, Defatting And Quality Improving Of Meat And Bone Meal

Meat and bone meal (MBM), a most commonly used high-protein feed in our country, hasbecome a promising replacement of fish meal in recent years. But the high crude fat contentand unstability of MBM restrict the application of MBM in feed industry. The paper studiedthe extrusion pretreatment and defatting process of MBM, the main contents were as follows:Quality status of15typical domestic MBM samples was analyzed. The results showed thatthere were big differences between different MBM samples, among them, histamine contentranged from2.0mg/kg to98.0mg/kg and the coefficient of variation was96.7%; the crude fatcontent ranged from6.2%to20.0%and the coefficient of variation was30.0%. The proteincontent of MBM was high and ranged from43.9%to59.5%; the lysine content of MBM washigh and ranged from1.56%to3.72%; MBM was rich in total phosphorus and it ranged from3.6%to5.7%. The vitro digestion rate of protein was in all circumstances high and theaverage value was83.9%, and it ranged from79.3%to88.0%. Compared to otherhigh-protein feeds, MBM was rich in fat and it was unstable, the defatting process wasneeded.In order to remove the fat of MBM efficiently, we applied the extrusion pretreatment. Theoptimal technological conditions were as follows: moisture rate of feed9.8%, sleevetemperature50oC, and rotating speed of screw rod140r/min. The permeation rate increasedfrom1.28mL/cm2·min to8.67mL/cm2·min. The residual oil rate was below1%and therewas no detection of the impurity in the oil. The effect of solvent, solid to liquid ratio andreaction time on defatting was investigated. The results showed that, in the condition ofhexane, solid to liquid ratio (w/v)1:3, and reaction time30min, good defatting result wasachieved. After alkali refining, bleaching, deodorization, refined animal oil was achieved.Acid value was0.90mg KOH/g, peroxide value was1.27mmol/kg and unsaponificationvalue was2.2%, which all met the requirements of feed industry. The oil was pale yellow, hadanimal oil aroma and can be directly used in feed industry.Accordingly, the effect of defatting on the quality of MBM was determined. The color andflavor of MBM was improved after defatting process and the indexes of defatted MBM canall meet the first level quality requirements of the feed MBM. The crude fat content of thedefatted MBM decreased from9.80%to0.37%, the crude protein content increased from54.50%to61.20%, in vitro digestibility of protein increased from86.01%to90.45%. Acidvalue was decreased from9.00mg KOH/g to2.60mg KOH/g. Furthermore, TVB-N valuedecreased from60.0mg/100g to40.0mg/100g and histamine content decreased from20.1mg/kg to19.6mg/kg by steam treatment for5minutes. Defatting process had improved thequality of MBM obviously. Finally, the quality of the defatted MBM during storage was studied. Compared withoriginal MBM and MBM supplemented with antioxidants, the acid value, TBA value andTVB-N value of the defatted MBM had a smooth growth at ambient temperature andhumidity. After8months’ storage, the defatted MBM didn’t have mildew phenomenon andrancid odor, which indicated that the storage stability was improved after defatting. Except forhistamine content, the other values changed relatively fast under relative humidity43.2%and30oC and accelerated in the longer storage time. Storage temperature had no significant effecton histamine contents. Under relative humidity69.9%and20oC, histamine content decreasedslightly, while other values increased rapidly. But obvious mildew phenomenon was observedafter6months’ storage. So the storage time of defatted MBM should not be over6monthsunder this condition.This paper provides basis for the improvement of the quality and the application of MBM.