Dairy Food Sciences

A Brief Review on Alkaline Phosphatase Methodology

Enzymes are organic catalysts which occur naturally in most raw foods. When milk is pasteurized most of the enzymes are inactivated or their activity is greatly diminished. The first reliable enzymatic test for determining efficiency of pasteurization was developed by Kay and Graham in England in 1933. It was based upon the inactivation of alkaline phosphatase.

Preparation of Casein from Skim Milk

Background on Casein

Casein is a mixture of phosphoproteins found in milk to the extent of about 3%. It contains all of the common amino acids an is high in the essential ones. Casein is often used as a dietary base for use in evaluation of vitamins, since it is easy to prepare casein as a pure protein. 
Casein is usually prepared by acid precipitation. It exists in milk as the water soluble calcium salt of a phosphoprotein. Acid treatment removes the calcium cation, leaving a water insoluble phosphoprotein.

Procedures for Oxidized Milk Problems

I. Check entire pipeline system for any part that is not made of stainless steel, rubber, or plastic.

  • Pipeline and pipeline fittings
  • Receiver jar and probes
  • Milk pump and attached valves, etc.
  • Filter, strainers, etc.
  • Bulk Tank - agitator paddle and rod, milk valve

II. Wash up system

Water Activity in Food

Water in food which is not bound to food molecules can support the growth of bacteria, yeasts and molds (fungi). The term water activity (aw) refers to this unbound water.

The water activity of a food is not the same thing as its moisture content. Although moist foods are likely to have greater water activity than are dry foods, this is not always so; in fact a variety of foods may have exactly the same moisture content and yet have quite different water activities.

A Summary of Titratable Acidity

  1. There are two fundamentally different methods of expressing acidity: (a) titratable acidity expressed as percent lactic acid, and (b) hydrogen ion concentration or pH. The former measures the total acidity but does not measure the strength of the acids. The pH indicates the strength of the acid condition.
  2. The true neutral point is at pH 7.0; pH values below 7.0 indicate an acid reaction; pH values above 7.O indicate an alkaline reaction.

Trans Fatty Acids - Information on fat, including definintions of key terms regarding fat.

Energy is stored in the body mostly in the form of fat. Fat is needed in the diet to supply essential fatty acids, substances required for growth but not produced by the human body. Dietary fat is needed to carry the fat-soluble vitamins A, D, E, and K and to aid in their absorption from the intestine. Fats are a group of chemical compounds that contain fatty acids. All fatty acids are molecules composed mostly of carbon and hydrogen atoms.

What is the Smoke Point of Butter?

There is not an easy answer to this one. Typical smoke points are provided in the table below. The smoke point is a straightforward measurement determined by heating the oil until visible smoke appears coming off the surface. It should be emphasized that these values are not absolute but approximations that vary depending on various aspects of the oil and its history. The smokepoint of oil depends to a very large extent on its purity and age at the time of measurement.

Introduction to Bacteria

Bacterial Names

Scientists use two names to describe each kind of bacteria. The first is the genus name and second is the species name. When the names of the species and genus are written, the are italicized, or underlined. The genus name usually refers to the group to which the bacterium belongs, somewhat like our human family names, except it is listed first. Many times the genus and species names (in the Latin or Greek language) are selected to describe some general feature of the bacterium.