Apples are brought to the processing building and dumped by the truckload or out of pallet bins, into a water-filled tank.
Apples are sorted to remove undesirable fruit that may be damaged or rotten and to remove debris such as twigs or leaves. The fruit can be sorted using computers that detect discoloration or other anomalies, human judgment, and flotation in water. They are then cleansed using air jets or jets of sterilized water.
To break the apples down into pieces that can be treated with enzymes and pressed for juice the fruits must go through a disintegrator, hammer mill, or grating mill.
Extraction may be accomplished through pressing chopped apple continuously or in
batches. There are a number of pressing systems: hydraulic cider press, bladder press, continuous screw presses.
Based on the construction solution, screw presses are classified as single- and double-screw type. The main advantage of a screw press is that the juice obtained has a much higher amount of soluble solids and bioactive compounds.
Apple juice is invariably cloudy and contains particles (bits of apple and press aid particles) that can be removed by screening. After juice extraction, the raw apple juice must be treated with enzymes to remove suspended solid materials. If not removed, this colloidal material can clog filters, slowing production and can cause the juice to form a haze later on.
The addition of pectinase facilitates the further break down of plant cells in solution which increases juice yield.
Another enzyme, amylase, is used in juice clarification. Amylase clarifies juice by breaking down starches that are suspended within the juice. These starches can cause a variety of undesirable effects such as cloudiness, gelling, slow filtration, and a dark brown coloration.
Many enzyme preparations are available both in liquid and powder forms. They are all subject to conditions that can influence enzyme performance such as pH, temperature, enzyme concentration and length of reaction time.
Apple juice is further clarified by using filtration membranes, fining, and heat clarification. A filtration membrane is a sheet of material that allows juice to flow through it but stops the passage of large particles, certain proteins, and microorganisms.
Flash heating the apple juice between 82 and 85°C will coagulate the particles that interfere with juice filtration. The juice must then be pasteurized to meet the FDA’s regulations.
Patulin is a mycotoxin found in apples and is produced by certain species of Aspergillus, Penicillium, and Byssochlamys. During processing of apple juice concentrates, it is possible to reduce patulin levels at all stages of production, and thus patulin level is being used as a quality indicator of apple juice.
Traditional packaging involves pasteurization at 80-88 °C, then filling and hermetically sealing the juice in glass containers or metal cans. Recently, laminated flexible packages have also been introduced with this process.
Production of apple juice
