ITDG 
Interdev Agroalimentaire  

Small-scale processing of peanut butter

	Type de fiche	Techniques/Technologies
	Mise en œuvre	ITDG(Royaume Uni)
	
	Zone géographique	; 
	
	Echelle d’action	Groupe
	Public(s) cible(s)	Small- and medium-scale food processors

Contexte
Peanut butter is a thick, light brown oily paste with the flavour of peanuts (groundnuts _ Arachis hypogaea).  It is used as a spread in some countries and in others as an ingredient in soups and stews.  In some places it acts as a substitute for vegetable oil.

Peanut butter is made from dried nuts, which are then roasted and ground into a thick paste.  The drying process preserves the peanuts.  In this form the peanuts have a long shelf-life, provided they are well dried and properly stored.  Transforming into peanut butter is for diversification rather than being an essential process to extend the shelf-life.

Heat produced during the processing destroys enzymes and contaminating micro-organisms. It also reduces the moisture content to one that is too low for microbial growth.  Peanut butter has a shelf life of several months if it is not exposed to strong light, air or heat.

Similar butters or pastes can be made from other nuts, for example almonds, cashews and hazelnuts.

Problématique / Objectifs
  Peanuts should be harvested when fully mature. If they are left in the ground too long after reaching maturity they lose flavour and colour. Lifting before maturity prodcues shrivelled nuts that are difficult to process.
  The nuts should be dried in the field while in the shell and then while on the stalks, turned upside sown.  Drying peanuts on iron sheets or a roof is not recommends because the nuts become baked and lose their flavour.
  It is essential to dry the nuts thoroughly to prevent mould growth beneath the shell and to shell them before storing. Some moulds produce aflatoxin, a poison which is highly dangerous and cannot be destroyed by processing.  All peanuts with traces of mould must be removed and destroyed.
  The nuts should be completely and uniformly roasted before grinding to produce a good quality peanut butter. Under-roasting produces a poor flavour while over-roasting leads to a darkened product and burned flavour.

Description/Mise en oeuvre
The processing of peanut butter follows these basic steps:

  Shelling and sorting
  Heating
  Cooling
  Cleaning and sorting
  Grinding
  Mix with salt
  Packaging and storage

A process flow sheet is available (ref link)

Shelling and sorting
Peanuts are shelled, either by hand or in a shelling machine. Mouldy and discoloured nuts are discarded.

Heating
Peanuts are roasted in an oven at 235 C for 40-60 minutes. This is best carried out in a rotary roaster to allow each nut to be uniformly roasted.  If this is not available, nuts can be roasted on an open pan, but should be turned constantly to prevent scorching.

Cooling
After roasting, nuts are rapidly cooled to room temperature to prevent them overheating.

Cleaning and sorting
The brown seed coat is removed by gently rubbing or brushing between the fingers. The dust and flaky seed coat is removed by winnowing. All discoloured nuts should be removed.

Grinding
The roasted peanuts are ground to a paste using a small stone mill, a disc mill, a low speed liquidiser or a pestle and mortar.  The choice of grinder depends on local availability and consumer preference. In some countries, smooth peanut butter commands a premium over peanut butter with pieces of peanut included.

Mix with salt
Salt (2% by weight) can be added to taste if desired. Some countries prefer the peanut butter to be totally natural, with no added salt.  The decision to add it depend on local taste.

Packaging and storage
Pack in pre-sterilised air-tight and moisture-proof glass or plastic jars.  Store in a cool place away from direct sunlight and strong heat.

Résultats/Eléments chiffrés
The following equipment is required:

Shelling machine (optional)
Rotary roaster or open flat pan
Grinding mill or liquidiser or mortar and pestle
Scales 
Glass or plastic jars

Enseignements
  Processors should pay strict attention to personal hygiene.  The product is often not re-heated before consumption and since it is a low-acid food, strict hygiene rules for food handling should be observed.
  During the rainy season, there is more chance of mould growth and aflatoxin development on the peanuts during drying.  Particular attention must be paid to the quality of raw materials to ensure there are no peanuts with mould in the processing batch.
  A shelling machine is not essential, but it can save a lot of manual work. Care should be taken when shelling the nuts by hand, to make sure that the nuts are not moistened as this can encourage mould growth. The decision to purchase (or use) a sheller will depend on several factors, including local availability, price and scale of operation.
  The degree of grinding and the size of the particles in the product depends on consumer preferences. In many countries a smooth paste has a higher market value than one that contains visible pieces of nuts.  Processors should carry out a survey to determine local preference and demand.
  Traditionally peanuts are ground by mortar and pestle, or with a stone rolling pin on a stone slab.  ITDG Zimbabwe has developed a peanut butter grinding machine with women users in Zimbabwe.
  With proper processing and storage, peanut butter can be stored for several months. The peanut butter should be kept away from sunlight, air and heat to prevent the development of rancidity in the oil. 

Auteur : Sue Azam Ali
Saisie le : 06/12/2001 

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