A cream separator was designed and fabricated in the workshop of FMPE Division in the year of 2019-20. The design was done based on the local farmer's practice in Bangladesh. The drawing of the machine was done in SolidWorks 2018 followed by Tut et al. (2010) for machine design and drawing.
Machine fabrication:
It has 25 numbers of the rotating discs and made of SS material. It has several kinds of spiral gear to transfer power from the handle to the rotating disc. The cream separator can be operated by manually or motor, which one is preferred by the customer. Salient features of different parts of the cream separator. Cream is a product composed of the higher-butterfat layer skimmed from the milk. Due to the high centrifugal force, that fat layer was separated from milk. First, fresh milk was fed in the bucket then transferred it to the uniform distributor through the tap. The machine could be operated by motor, leg, or hand. When the speed of the handle would be 50-60 rpm then then the bucket tap allowed the milk to come in a rotating disc and milk would fall down. There are 25 numbers of the rotating disc that rotate around 7200-8000 RPM in the rotating holder. When fresh milk would pass through the rotating disc, cream or fat and skimmed milk would be separated by centrifugal force. Because fat is little bit lighter in weight than skimmed milk. The skimmed milk would heat on the rotating disc holder's inner surface and come out through the lower outlet. On the other hand, the cream would not go far from the central axis and it would come out through the upper outlet.
Milk sample:
About 100 kg of fresh milk was collected from a local dairy farm. We did this experiment three times for measuring the accuracy of the machine. After separating the cream, it was cooked until Ghee appeared in the fry span.
Determination of TSS:
The total soluble solids (TSS) were determined as per method described by Mazumdar and Majumder (2003) using Digital-Bench Refractometer. Before use, the instrument was cleaned and adjusted to zero at 20°C using distilled water. An appropriate quantity of sample of each product prepared was placed on the prism-plate of the refractometer with the help of a glass rod and folding back the cover. For each sample, the instrument was calibrated using distilled water. The reading appeared on the screen was directly recorded as total soluble solids as brix.
Determination of pH:
For determination of pH in the products, a method of AACC (2000) was adopted and digital pH meter was used. Sample solution was taken in the beaker and directly inserted the electrode into the solution. When the first reading was completed, the electrode was wiped with distilled water and dried-up with tissue paper. Similarly, as a continue series, all other samples were determined accordingly.
Determination of Fat:
The Soxtec™ 2045 extraction unit is a fully automated system for fast and safe determinations of milk fat. For total fat analysis, the Hydrocap filter was transferred from the hydrolysis unit to the extraction unit which then performs the four extraction steps boiling, rinsing, solvent recovery and auto shut down, fully unattended.
Determination of protein:
The nitrogen present in the sample was converted to ammonium sulphate by digestion at flask with sulphuric acid in presence of a catalyst, potassium sulphate and mercuric oxide. Acid liberated by distilling the digest with sodium hydroxide solution was absorbed by boric acid titrated for quantitative estimation.
Separation efficiency (Es):
Separation efficiency depends on initial milk fat content and residual fat in the skim. Cream or butter separation efficiency can be expressed by the following formula (Goff, 1993).
Es = (1 - fs/fm ) × 100 (1)
Where, fs = skim fat as percent (w/w), fm = milk fat as percent (w/w).