Manuf. The process of making butter by the common operation of churning is extremely simple, and is well known. The chief objects to attend to are maintaining a proper temperature, and a certain degree of exposure to the air. Extreme cleanliness must also be observed; the churn and other utensils being frequently scalded out with water. When the butter is ‘come,’ it should be put into a fresh-scalded pan, or tub, which has been standing in cold water, cold water poured on it, and after it has acquired some hardness, it should be well beaten with a flat board until not the least taste of the butter-milk remains, and the water, which must be often changed, becomes quite colourless and tasteless. A little salt may then be worked into it; after which it may be weighed and made into ‘forms,’ which should then be thrown into cold water contained in an earthen pan provided with a cover. In this way nice and cool butter may be obtained in the hottest weather.
At Dumbarton the newly separated butter is put into a clean vessel, and a corn sickle is drawn several times crosswise through it, to extract any hairs that may adhere to it. This operation is performed in very cold spring water, and is followed by thoroughly washing it therein. 10 oz. of salt are now added to every stone-weight of the butter, and well mixed in.
In Devonshire the milk is generally scalded in copper pans over a charcoal or wood fire, and the cream collected as soon as it rises, or, and more frequently, when the whole has got cold. It is then churned in the usual way. On the small scale the butter is commonly obtained from this cream by patiently working it with the hand in a shallow pan or tub. Without care the cream is apt to absorb some of the
fumes from the charcoal, which impart a peculiar taste to the butter. This is the reason why some of the Devonshire butter has a slight smoky flavour. It may be removed by thorough washing in cold water. Of late years, in the large dairy-farms of Devonshire, covered flues, with openings to receive the bottoms of the pans, have superseded open fires, by which the danger of contamination from the fumes is removed.
Choice. Fresh butter has a pleasant odour and is of an equal colour throughout its substance. If it smells sour, the butter-milk has not been well washed out; and if it is streaked or veiny, it is probably mixed with stale butter or lard. A good way to try butter is to thrust a knife into it, which should not smell rancid and unpleasant when withdrawn. Rancid and stale butter, when eaten in quantity, is capable of producing dangerous symptoms.
Pur. The cheaper kinds of butter are frequently adulterated with common wheat-flour, oatmeal, pea-flour, lard, and is sometimes mixed with suet and turnips, as well as with a large quantity of salt and water. The trick is concocted between the Irish factors and the London dealers. The higher priced article is seldom mixed with anything beyond an excess of salt and water, notwithstanding the assertions of alarmists to the contrary. The presence of lard may be detected by the flavour and paleness of the colour. A little of the sample adulterated with the other substances named, if melted in a glass tube or phial, will separate into strata, which are very marked when cold.
Quantitative Analysis of Butter.—1. The following process for the analysis of butter, by Mr A. H. Allen, is extracted from the ‘Chemical News’ (xxxii, 77):—The Society of Public Analysts has adopted 80·00 per cent. as the lowest limit of fat contained in a genuine butter.
The amount of water is best ascertained by heating 5 grams of the butter in a small weighed beaker to a temperature of about 110° or 120° C. for an hour or so. Some chemists merely heat the butter on a water bath. According to the author’s experience, perfect drying is next to impossible at that temperature.
The dried butter is next treated in the beaker with anhydrous ether, or commercial benzoline. The former liquid is expensive and inconveniently volatile, while it must be used in a perfectly anhydrous condition (to avoid solution of the salt), and except when boiling has but a limited solvent power for butter, especially when adulterated. Benzoline dissolves fat more readily than ether; it does not volatilise so rapidly at ordinary temperatures, it is always anhydrous and has the advantage of low price. The “benzoline” employed by the author is made by redistilling the commercial article from a retort immersed in a bath of boiling water. About one third of the original bulk usually comes over readily at 100° C., and has a gravity of 0·689.
On warming the beaker containing the benzoline the dry butter readily dissolves. The liquid is poured on a small dry filter and washed with warm benzoline, the filtrate being collected in a small wide beaker. If the filter had been previously weighed, its increase of weight, after careful drying, will of course give the quantity of curd and salt in the 5 grams of butter taken. Except in cases in which extreme accuracy is desired, it is preferable to scrape the residue off the filter and weigh it separately.