The two most common methods of blanching involve passing products through an atmosphere of saturated steam or a bath of hot water. Common types of steam blanchers include tunnel-type units, in which products are carried on a meshed conveyor belt through a tunnel containing steam, screw-conveyor units, in which products are transported through a steam chamber using a screw-type conveyor, and fluidized bed units, in which a mixture of air and steam transport and heat the product simultaneously . Two common types of hot water blanchers are the reel blancher, in which products are moved through a hot water bath in a rotating drum with internal flights, and pipe blanchers, in which products are fed into and out of a pipe containing recirculated hot water.In the canning process, fruits and vegetables are sterilized and preserved in hermetically sealed containers that prevent microbial spoilage. The basic canning process consists of five unit processes: filling, exhausting, sealing, heat sterilization, and cooling. After fruits and vegetables have been subjected to the applicable raw materials preparation processes, they are filled into containers typically made of glass or metal. Most filling is done by machine, but occasionally hand filling is also performed. Brush fillers are commonly used for solid products, while rotary piston fillers are commonly used for liquids, pastes, plastic round plant pots and powders. Containers are typically filled from 90% to 94% of full capacity, leaving a headspace that is necessary for forming a vacuum .

Prior to filling, containers are typically cleaned using hot water, steam, or a blast of pressurized air.After filling, it is common for containers to undergo exhausting, the purpose of which is to remove air from the container such that a vacuum is formed. The vacuum helps to keep the can ends drawn inward, reduces the strain on containers during processing, and minimizes the amount of oxygen remaining in the headspace . Often, air is exhausted from the headspace using a blast of steam. Immediately after the headspace is exhausted, the container is sealed mechanically through the application of a container lid. In most modern types of sealers, exhausting and sealing occur almost simultaneously on the same piece of equipment. Once containers are sealed, the products are subjected to in-container heat sterilization, a process which destroys micro-organisms in the product via the application of heat. The temperature and duration of the heat sterilization process depend on both the product and the size of the container. The two most common types of heat sterilizers in use today are continuous rotary sterilizers and hydrostatic sterilizers . In continuous rotary sterilizers, containers are fed into a rotating cylindrical heat chamber, which is typically heated by steam. A mechanism inside the chamber rotates the containers about their own axes as they are heated while also transporting them along the length of the chamber. In hydrostatic sterilizers, containers are fed continuously through a steam chamber that is isolated by water columns at the chamber entrance and exit. After heat sterilization, the containers are quickly subjected to cooling in order to prevent overcooking.

Many rotary sterilizers are equipped with a cooling stage that can use pressurized air or water as the cooling medium. Stand alone container cooling units that use water sprays at ambient pressure for evaporative cooling are also sometimes employed. In hydrostatic sterilizers, containers are cooled by passing through a long trough of cooling water before exiting the system. Aseptic canning is an alternative method of canning that is applicable to liquid and semiliquid products . In aseptic canning, foods are sterilized and cooled separately before being filled into sterilized containers in a sterilized environment. Continuous heat exchangers are used to sterilize and cool products as they flow into an enclosed filling chamber, which is kept in a sterile condition via ultraviolet light and filtered air. Because containers are not required to withstand high sterilization temperatures, alternative container materials are commonly used, such as laminated cardboard and plastics .In addition to blanching and heat sterilization, there are several other important unit processes employed in fruit and vegetable processing that are based on the application of heat. Among the most common thermal processes are evaporation, pasteurization, drying and dehydration, and frying. In evaporation, heat is used to remove water contained in fruit and vegetable pulps and juices to produce a more concentrated product. Evaporation—which is sometimes referred to as concentration by boiling—is used most notably in the production of tomato purees, juices, and pastes, and fruit and vegetable juice concentrates.

While there are many different types of evaporators, the two most common types found in modern food processing operations are falling film evaporators and forced circulation evaporators . In falling film evaporators, liquids fall by gravity down the inside surfaces of tubes arranged in a shell-and-tube heat exchanger configuration, with steam as the primary heating medium . In forced circulation evaporators, liquids are circulated by a centrifugal pump at high velocity through a heat exchanger, which is also typically heated by steam . A common approach to energy efficiency for evaporators is to use the hot vapors that boil out of the liquid in one evaporator as the heating medium in another effect, which is operated at a lower pressure. This approach is called “multi-effect” evaporation; in practice, up to five effects are feasible in evaporators in food processing . Pasteurization is a mild thermal treatment process used for liquids, such as fruit and vegetable juices, in which the liquids are heated to below 100° C for a sufficient amount of time to destroy pathogenic micro-organisms. Unlike heat sterilization, which destroys all micro-organisms, the pasteurization process does not kill heat-resistant micro-organisms. Thus, pasteurized products have a shorter shelf life than heat sterilized products and, in the case of pasteurized fruit and vegetable juices, must be refrigerated and consumed in a timely manner. Continuous pasteurization processes are most commonly used in fruit and vegetable processing. In the basic process, liquids flow through a heat exchanger, which can use either hot water or steam as the heating medium, where they are heated for the required residence time to kill pathogens. Common heat exchanger configurations include plate heat exchangers, tubular heat exchangers, shell and tube heat exchangers, and spiral heat exchangers . After heating, liquids typically flow through a regenerator and then to a cooling stage. Drying and dehydrating processes preserve fruits and vegetables by removing moisture to retard or prevent the growth of micro-organisms. The oldest and most basic method is sun drying, in which fruits are harvested and spread out on tarps or trays to dry in the sun. This process is still used throughout the world for such fruits as grapes and figs . However, most fruits and vegetables are currently dried using heated drying equipment. Continuous belt driers are among the most common driers used in fruit and vegetable processing. In a continuous belt drier, products are carried on a meshed conveyor through a tunnel in which hot air is circulated. Other common driers include spray driers, drum driers, vacuum driers, fluidized-bed driers, nft hydroponic and belt-trough driers .Mechanical separation processes for fruits and vegetables generally involve the separation of liquids from liquids or liquids from solids using mechanical means, primarily in the manufacture of juice products and concentrates. Mechanical expression is a widely used process for extracting fruit juices, in which high pressures are applied to fruits using a pressing action to rupture cell walls and express juices. Expression is typically done using batch presses or continuous presses. Common types of batch presses include basket presses, hydraulic plate presses, and tank presses. Many continuous presses are of the screw type, in which fruits are fed into a barrel with a rotating helical screw that increases pressure on the fruits as they are fed along its length . The centrifugation process is used for separating pulps and small particles from juices, and can also be used for separating citrus oils from citrus juices. The basic component of a centrifuge is a rapidly rotating mechanism that exerts centrifugal force, which separates different juice constituents based on their densities . Centrifugation can also be used in the freeze concentration process, which is discussed below. Membrane concentration can be applied to concentrate fruit and vegetable juices in lieu of or as a precursor to traditional evaporation methods of concentration. In membrane concentration, water can be separated from juice solids using pressure as a driving force across a semi-permeable membrane .

Because membrane concentration does not require a phase change , it can offer a more energy-efficient option of juice concentration.Refrigeration systems are used throughout the U.S. fruit and vegetable processing industry to produce chilled water for process cooling, for refrigerated storage, and in product freezing applications. Some of the most common unit processes related to refrigeration and freezing used in fruit and vegetable processing are discussed below. Cold storage involves the storage of products in refrigerated rooms and can be used at several stages of fruit and vegetable processing. After harvest, some fruits and vegetables are placed in cold storage to delay ripening and to maintain quality so that processing seasons can be extended . Cold storage is also used extensively for finished frozen products to keep them at the desired temperature prior to shipping. Also, some facilities can use cold storage to keep purchased ingredients fresh until required for further processing. In freezing, the temperature of fruits and vegetables is reduced to a level sufficient to retard microbial activity. The three major types of freezing processes used in fruit and vegetable processing are: individual quick freezing, freezing in the container, and immersion in a freezing solution . Individual quick frozen products are frozen before packaging using fluidized-bed or air-blast freezers, both of which rely on the circulation of chilled air. Products frozen in the container can be frozen using plate freezers, in which containers are sandwiched between two refrigerated plates, or air-blast freezers. In immersion freezers, packaged products are passed through a bath of refrigerant on a submerged mesh conveyor . Freeze drying is a process for dehydrating vegetables and fruits using a combination of freezing and low pressure. In the freeze drying process, products are first frozen and then placed in a chamber under high vacuum. In the vacuum chamber, the water in the products is transformed directly from ice into the vapor phase and is condensed on refrigerated coils . While freeze drying can produce dried fruits and vegetables with better color, odor, and flavor retention than traditional drying methods, the cost of freeze drying can be up to four times greater than traditional methods . In freeze concentration, fruit juices are concentrated using a combination of freezing and mechanical separation. First, fruit juices are frozen to produce a slurry of frozen fruit liquids and ice crystals. Next, a separation device is used to separate the ice crystals from the fruit liquids. Freeze concentration is said to produce fruit juice concentrates without appreciable loss in taste, aroma, color, or nutritive value . However, the high capital and refrigeration costs associated with freeze concentration might make it attractive for only high-value juices and extracts .In addition to the major unit processes discussed above, unit processes related to product conveying, mechanical mixing, and packaging are also ubiquitous across the fruit and vegetable processing industry. The conveying of fruits and vegetables throughout a facility can be done either mechanically or hydraulically, depending on the product form. For solid products, common forms of conveying include belt conveyors, flight conveyors, screw conveyors, bucket elevators, and water flumes. For liquid and slurry products, pumps and piping networks are the most common form of transport throughout a facility. For both solid and liquid products, surge bins and tanks are commonly used as surge buffers in the production system . Mechanical mixing processes are typically employed to blend ingredients and to homogenize product consistency at various stages of fruit and vegetable processing. Although there are many different types of mixing equipment, the most commonly used varieties in fruit and vegetable processing include flat blade agitators, vaned disc impellers, and propeller agitators . The unit processes related to packaging generally include automated operations for can labeling, shipping box assembly, shipping box packing, palletizing, and pallet shrink wrapping.