Membrane Application for Food Industry

M.PIZZICHINI; ENEA – innovation Area, processes and materials department; C.R.E. Casaccia, Roma, Italia
food industry
Agroindustrial processes generally involve the transformation of natural foodstuff into useful, non perishable, commercial products.
Recent developments in processing technologies, packaging and materials have made possible the development of a whole new food manufacturing industry capable of satisfying the modern trends of human food.

As a result, a new food service industry has emerged, supplied by food manufactures with high-quality, especially developed products, packaged in large container, refrigerated, thermally processed or frozen.

In developing countries food must be available and accessible to every person in nutritious, safe and appetising forms. This means that every consideration must be given to the entire food chain, from production to processing, distribution, consumption, and biological utilization.

The application of innovative techniques such as Membrane Technology (MT) in food transformation processes represents a real opportunity to increase and quality the productivity and reduce the environment pollution of farms. The commercial application of MT in food processing industry includes concentration of oil emulsions, blood treatment for proteins recovery, clarification of wine, concentration of fruit juices and treatment of a variety of food processing waste stream.

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In general, MT’s are applied in different unit operations: concentration, purification, clarification, recovery and upgrading of products.

These operations allow to increase the product quality (taste, aroma, apperance,…), the recovery of process byproducts and a high reduction of the process energy consumption. In addition, MT permit a strong reduction of chemicals used for clarification or flocculation of raw natural compounds such as wine, vinegar, beer, fruit juices, coffee, tea, etc.

Membrane processes such as cross-flow MF, UF and RO, all pressure driven membrane process, have been intensively exploited in the food industry. In this field many products such as juice, milk require removal of large quantities of water to concentrate the products for more efficient packaging or shipping.
Table 1. Example of the use of membranes in the food and beverage industries. From Jone (1987)

Food industry

Application area

Membrane processes

Milk Concentration of whole milk and skim milk RO, UF
  Concentration of chesse whey RO
  Fractionation of whole milk or cheese whey RO
  Separation of inhibitors of micro-organism growth for fermentation UF
  Recovery of whey protein from wastes UF
  Hydrolysis of lactose for low lactose milk ENZYME
  Removal of casein, fats and lactose from whey MF, RO
  Demineralisation of whey ED
Fruit juice and vegetable juice Fractionation and clarification of apple, vegetable and citrus juices MF, UF
  De-acidification of juices UF
  Concentration of fruit juice RO
  Sterilization of juice prior to bottling of fermentation MF, UF
  Color modification UF
  Recovery of pectin from wastewater of orange juice canning UF, RO
  Recovery of wine or juice from lees MF
  Sterilisation of juice prior to fermentation (controlled) MF
  Clarification and sterilization after fermentation UF
  De alcoholisation RO
  Recovery of reuse water UF, RO
  Vinegar clarification MF, UF
  Molasses – removal of heavy sugars and color, separation of sucrose and hexoses RO
  Desalination of molasses RO, ED, CD
  Cane juice concentration RO
  Sugar waste recovery RO
  Extracts, concentration RO
  Decaffeination RO
Meat stocks, soups, jams, jellies Concentration   RO, UF
Protein process Concentration of egg-white UF, RO
Soy protein concentration UF
  Separation of emulsifiers from enzyme treated soybean extract UF
  Separation of color and salts from hydrolysed vegetable protein UF, RO
  Removal of odour from soybean milk UF, RO
  Clarification of raw and heat treated soy sause MF
  Recovery of protein from wastewater from ham and other food processing operations UF, RO
  Whole egg concentration UF
  Concentration of rennet UF, RO
  Gelation dehydration (concentration) UF

A substaintial difference between MT and the conventional filtration (dead-end filtration) regards the operation mode, as schematized in Figure 1. In the same figure the morphology of microfiltration membranes are reported.

In MT, the membrane module is operated in a continuously self-cleaning mode, with solutes and solids swept away by the concentrate stream which is running parallel to the membrane surface, hence the term “cross flow” or tangential filtration. In MT the concentrate stream, retained by membrane, can be recirculated through the module in order to obtain the desired concentration ration (VRC). This parameter is given by the ratio between feed volume and final concentrate volume.

Contrary to the distillation process, in MT the separation takes place in isothermal conditions without phase transition, with the opportunity for reusing both concentrate and permeate streams. This permits an energy saving and a low environmental impact, because no byproduct are generated during the seperation process.