There are much longer time intervals between the different production stages in agriculture when compared to food processing. Several months may elapse between ploughing, weeding and harvesting, and the size of equipment for the different tasks does not therefore need to be matched. In food processing, the stages in a process are often separated by a few minutes or hours, and all equipment must have a similar throughput to avoid delays caused by one piece of equipment being too small. It is therefore necessary to take account of the whole process when selecting equipment. In this section, the methods and equipment that are suitable for village processing of the products listed in Table 6 are described. Most are simple techniques, which require only household equipment such as knives and pans at micro-scale of production. Specialized equipment necessary for higher production levels is identified.
There is a wide range of bakery products that can be made at a small-scale including biscuits, cookies, leavened or unleavened breads, cakes, flans, pastries, pies, pizzas, samosas and scones. Each can be made with different shapes, sizes, flavours, etc., and the range of potential products is therefore extremely large. Production of selected products is described in outline below.
Bakery products rarely cause food poisoning because the heat during baking reduces the numbers of micro-organisms to safe levels. However, products such as pies that contain meat, fish or vegetables, or cakes that contain cream have a greater risk of causing food poisoning. Pies should be stored in a refrigerator or in a hot display cabinet. Products that contain cream should be stored in a refrigerator. Careful food handling and thorough cleaning of equipment are essential to produce these products safely. Most products from small-scale bakeries are not packaged, except in simple polythene or paper bags to protect them from dust and insects. However, biscuits require more sophisticated packaging for a longer shelf life, and are packed in cartons covered with a moisture-proof and airtight film such as cellulose, polyester or polypropylene, or stored in airtight tins or jars.
The main item of equipment in a bakery is the oven, and this can be built by a local bricklayer. Ovens can be either heated internally (Figure 4) or have a separate firebox. Internally heated ovens are simple and relatively cheap to construct, but the food can be contaminated by smoke and ash from the burning fuel. Fuel is burned on the hearth for a few hours and the embers are raked out before the dough is baked. A new fire is built to reheat the oven after a few batches. An externally heated oven consists of a brick or earth structure that contains a steel baking chamber (e.g. an oil drum) over the firebox. This design provides for continuous baking without the need to re-light the fire, has good fuel economy and no contamination of products by smoke or ash. Fuelwood is cheap or free in rural areas, but in many countries deforestation has resulted in increased costs and legal restrictions on its use. Wood also produces a light fluffy ash that can easily contaminate products. Charcoal is more expensive, but it produces an intense heat with little smoke. However, restrictions on charcoal burning may also apply in areas that are suffering deforestation. Where coal is available, this is the ideal fuel for bakery ovens.
Doughs and batters need to be evenly mixed, and a mixer is an important piece of equipment in a bakery. Mixing by hand is possible at microscale, but when larger quantities of dough are required an electric mixer is necessary. A simple proving cabinet for fermented doughs can be made from a wooden framework, covered in polythene sheeting, with a gently boiling pan of water inside. Dough is placed in the cabinet on racks for the required time. Commercial bakeries also require a range of baking trays and tins and small hand-tools, such as biscuit or pastry cutters, flour sieves, glazing brushes, rolling pins and whisks.
FIGURE 4 Bakery oven near Tarapoto, Peru. (Photo, Rios, 1996)
Breads. Leavened bread is produced by mixing together "strong" wheat flour, yeast, water, fat and salt to form dough. This is then kneaded and placed in a prover to allow the yeast to expand the dough with gas. It is then divided into the correct sized pieces and proofed again to allow the dough to relax. After "knocking back" to remove large gas bubbles and a final proof to allow the yeast to gently inflate the dough, it is baked in an oven. Differences in the amounts of ingredients and the conditions used at each stage of the process give rise to the wide variety of breads that can be produced. Dough for unleavened flat breads, tortillas, etc., is prepared and rolled thinly before baking on a hotplate. Batter-based breads are made by mixing the ingredients to form a uniform batter, and then pouring a portion on to a hotplate. After a few seconds, the bread is turned over and the other side is baked.
Biscuits dough is made by mixing flour, sugar, baking powder and egg, together with any nuts, dried fruit or flavourings that are required. It is rolled out and cut to the required shapes with biscuit cutters, and decorated as required (e.g. with sugar crystals, chocolate chips, crystallized fruit, etc.) and baked until golden brown.
Pastries are made by first boiling together water, butter and salt. Flour and then egg is added, beating all the time until the paste is smooth and shiny. It is piped on to trays as "finger" shapes, or "rounds" and baked in an oven. Alternatively, pastry cases can be filled with many different types of sweet or savoury fillings.
Cakes, scones or soda bread rely on gas produced from baking powder to produce an aerated product. There are two main methods of making cakes: 1) Fat or butter is beaten with sugar to create a light foam, and any colouring or essences are added. Then egg is mixed in and flour/baking powder is carefully folded it into the batter, and 2) sugar and egg are whisked to form a batter. The flour is carefully folded into the mixture until it is smooth. In both methods, other ingredients (fruit, nuts, etc.) are then blended into the batter and it is poured into baking tins and baked in an oven. Scones are made by rubbing in margarine into the flour and baking powder to form a crumb. Sugar and dried fruit are added to form dough. It is rolled out to the required thickness and cut into round shapes using a biscuit cutter. These are baked on a hotplate until browned on each side. Soda bread is similar to bread made with yeast, but uses baking powder to aerate the dough.
Wines and beers
Wines are produced from fruit juice or pulp by fermenting sugars into alcohol using "wine yeasts". Almost any fruit can be used, but the most popular are pineapple, papaya, grape, passionfruit, banana, melon and strawberry. Beers are produced using different varieties of yeast, by fermenting a mash of cereal grains (sorghum, maize, etc.) that have been allowed to sprout. The main equipment is narrow-necked fermentation vessels, made from food grade plastic or glass and plugged with cotton wool or fitted with an air lock (Figure 5). After fermenting, wine is filtered through a muslin or nylon cloth and siphoned into clean containers and allowed to clear before it is bottled. A clearing agent such as bentonite is needed to produce a crystal-clear product with some types of fruit. Beer is filtered and either sold from the container or filled into bottles.
Juices, squashes and cordials
FIGURE 5 An airlock used in wine making. (Source: Fellows, 1997)
The consumption of juices, especially pineapple, passionfruit and citrus juices is increasing in urban centres in many countries. Juice can be extracted from fruits in a number of ways, depending on the hardness of the raw material. Soft fruits, such as melon and pawpaw, can be pressed in a fruit press, pulped using a juicer attachment to a food processor, or "dissolved" in a steamer. Citrus fruits are "reamed" to extract the juice without the bitter pith. Harder fruits, such as pineapple are peeled and pulped using a liquidizer. At large-scale operations, a pulper-finisher separates skins and seeds from the pulp. When a clear juice is required, it is filtered through a fine cloth or stainless steel juice strainer. Juices are filled into bottles and pasteurized in hot water. Juice production from seasonal fruits can be spread over a large part of the year by processing a sequence of fruits, or by part-processing pulps and storing them in a preservative such as sodium metabisulphite solution. Squashes are made from fruit juice mixed with sugar syrup. Cordials are crystal-clear squashes. A sugar syrup is heated to boiling and mixed with filtered juice in a stainless steel pan, before filling into bottles. These drinks are diluted with water and used a little at a time, so they may contain a preservative (usually sodium benzoate) to prevent spoilage after opening.
Sweets are made by boiling sugar syrup to remove water. Awide variety of confectionery products are possible by varying the ingredients, the temperature of boiling, and the method of shaping the sweets. Fondant is made by boiling sugar syrup with glucose syrup. It is then cooled and beaten to reduce the size of the sugar crystals. Creams are fondants that are diluted with a weak sugar solution. They have a shorter shelf life because of the higher water content. Gelatine sweets including gums, jellies, pastilles, and marshmallows have a spongy texture, which is set by gelatine. Toffee and caramels are made from sugar, milk and fat. Hard-boiled sweets are made from sugar syrup with added flavourings and colourings, which is boiled to a high temperature and then cooled to form hard products. For each product, the temperature of boiling can be measured using a sugar thermometer, or a sample of product is cooled and, when cold, it is checked for the correct texture. The boiled mass is poured onto a metal, stone, or marble table to cool the product uniformly before it is shaped by hand and cut into pieces. Sweets can also be made using moulds made from rubber, plastic, metal or wood. Starch moulds are made by making impressions in a tray of corn flour, using wooden shapes. In areas of high humidity, unpackaged sweets absorb moisture from the air and become sticky. Waxed paper, aluminium foil or plastic films are used to wrap individual sweets by hand. Sweets can also be stored in glass jars, or tins with close-fitting lids.
Drying
Dried foods can be "high-volume, lower-value" (e.g. staple cereals or root crops), or "low-volume, highervalue" foods (dried fruits, vegetables, herbs and spices and dried meat and fish). This second category offers better opportunities for profitable production by small-scale processors. Drying removes most of the water from foods to extend their shelf life and to increase their convenience and value. The loss of weight also makes transport cheaper and easier. Care and attention to hygiene are essential during drying, especially when processing low-acid foods such as meat or fish. The temperature during drying is not usually high enough to kill any bacteria or moulds that contaminate the food and, when the food is rehydrated, they can grow again and cause spoilage or food poisoning. Polythene film is only suitable for storing dried or smoked foods for a short time before they pick up moisture, soften and go mouldy. Polypropylene gives a longer shelf life, but it is usually more expensive and it may not be available in many countries. Sealed earthenware pots or metal tins are suitable alternatives for home storage.
Blanching prevents changes in colour, flavour and texture during storage of dried vegetables. Sliced vegetables are heated for a short time in a wire basket in hot water. Sulphur dioxide prevents browning in dried foods such as apple, apricot, pineapple, root crops and coconut. In sulphuring cut or shredded foods are exposed to burning sulphur in an enclosed cabinet. In sulphiting the food is soaked in a solution of sodium sulphite or sodium metabisulphite. dioxide. In some industrialized countries, there is increasing consumer resistance to fruits that are treated with sulphur, and if products are considered for export the local export development board or export agents should be consulted about its use. Dipping in citric acid, lemon or lime juice is also sometimes used to prevent browning of light coloured foods. Syrup pre-treatment can be used to extract some of the water from fruit pieces before drying. Fruit is boiled for a few minutes in syrup and soaked overnight. This produces a succulent, soft texture in the dried product.
Sun drying is only possible in areas where the weather allows foods to be fully dried immediately after harvest. The main problems are:
Solar dryers protect foods from dust and pests and they increase the rate of drying compared to sun drying. They can be constructed from locally available materials at relatively low cost and there are no fuel costs. However, the extra investment in dryer construction may not be recovered by higher income if local consumers are not willing to pay higher prices for improved quality. Highvalue products, particularly for export, may justify investment in a fuel-fired dryer. These are more complex and expensive to build or maintain, and require skilled labour for their operation. A compromise is to fit a fuel-fired heater to a solar dryer to give better control over drying conditions, to allow drying at night or in cloudy weather and produce a higher quality product.
Smoking. Two methods of smoking (cold and hot smoking) are used. Cold smoking changes the colour and flavour of the food, but it is not cooked or preserved by the process. Hot smoking cooks and dries the product as well as changing the colour and flavour. Locally-constructed smokers can be made from wood or brick. They may have an external smoke generator or the smoke can be produced in the smoking chamber. "Forced draught" smokers have a fan between the firebox and the smoking chamber or in the chimney. These give greater control over the time and temperature of smoking. With all types of smokers, the temperature and smoke density can be controlled by adjusting the air supply to the smouldering wood.
FIGURE 6 Combined solar and fuel-fired dryer. (Photo by the author)
Jams, jellies and marmalades
FIGURE 7 Jam making. (Photo by the author)
Jam is made from fruit pulp or juice with added sugar and sometimes added pectin or citric acid. Jellies are crystal-clear jams made from juice that is filtered through a fine cloth, instead of using fruit pulp. Marmalades are produced from clear citrus juices and have fine shreds of peel suspended in the gel. The high sugar content and acidity of all preserves prevents mould growth after opening the pack so that it can be used a little at a time. These products are made by boiling fruit pulp/juice with sugar in a stainless steel pan to concentrate the mixture. For some fruits that have little natural pectin (e.g. melon), powdered or liquid pectin is added. The correct point to stop boiling can be checked using a jam thermometer, by placing a drop of the product in cold water to see if it sets, or by using a hand-held refractometer. However, a refractometer is likely to be too expensive for many small-scale processors. Preserves are hot-filled into glass or polypropylene containers using jugs and funnels.
Pastes, purees and fruit "cheeses"
The most common types of pastes and purees are tomato and garlic, which are widely used in cooking. The high solids content and natural acidity preserve them for several weeks, provided they are properly packaged. They can be made at a small-scale by carefully boiling the pulp in a pan with constant stirring to prevent it darkening or burning. An alternative method of making tomato paste is to hang the pulp in a sterilized cotton sack and allow the watery juice to leak out. Salt is then mixed in and it is hung again until the weight falls to one third of the original. This method produces a product that has a natural flavour and uses considerably less fuel than boiling (deKlein, 1993). Fruit cheeses are fruit pulps that are boiled until they set as a solid block when cooled. They can be cut into bars or cubes to eat directly or small pieces can be used in confectionery or bakery products.
Pickles and chutneys
There is a wide variety of pickled fruits and vegetables. Fermented pickles are made from vegetables such as cucumber, cabbage, olive or onion using lactic acid bacteria to ferment sugars in the food to lactic acid. Unfermented pickles are vegetables packed in jars with vinegar, salt and sometimes sugar and pasteurized in a bath of hot water. Sweet pickles are made from single fruits or mixtures of fruits and vegetables. They are preserved by the combined action of lactic acid or vinegar, sugar and in some cases added spices. Pickles may be packed in small quantities in sealed polythene pouches, or in plastic pots. Salted vegetables are made in a drum by building up alternate layers of chopped or shredded vegetable (e.g. cabbage) with layers of salt. The salt draws out water from the vegetables to form a concentrated brine, so products can be kept for several months. The salt is reduced by washing the vegetables before they are eaten. Chutneys are thick, jam-like mixtures made from a variety of fruits and vegetables, sugar, spices and sometimes vinegar. The high sugar content and acidity preserves the product. Some products are boiled which pasteurizes them, and others are allowed to ferment so that acids produced by the bacteria preserve the product. Some spices such as ginger, mustard, chilli and garlic also have a preservative effect. In the process, ingredients are boiled until thickened and packaged in a similar way to pickles.
Sauces
Tomato sauce, chilli sauce and mixed fruit sauces such as "Worcester" sauce are thick liquids that are made from pulped fruit and/or vegetables. They are boiled together with salt, sugar, vinegar and spices (e.g. cinnamon, cloves, allspice or cayenne pepper). The acidity, salt and sugar prevent spoilage after the pack is opened. On a small scale, the ingredients are heated in stainless steel pans with constant stirring to avoid burning the product, and packed in bottles.
FIGURE 8 A range of chilli sauces. (Photo by the author)
Sliced root crops (yam, cassava, sweet potato, Irish potato, etc.) and a number of starchy fruits, (jackfruit, breadfruit or banana) can be fried and eaten as snack foods. No specialized equipment is required at microscale production, but on a larger scale, a deepfat fryer and a slicing machine can be used to produce more uniform products and reduce the time and effort involved in processing. They can be stored for a short time in polythene bags, but rapidly develop a rancid flavour. Polypropylene film is needed for longer storage. Doughnuts are made by fermenting dough made from water, flour, sugar and yeast and made into balls. Ring doughnuts are made by removing the centre from the dough piece with a cutter. The dough is fried in deep oil until all sides are golden brown. Doughnuts can be coated with sugar or filled with jam or cream. Samosas are triangular packages of "filo" pastry, which are filled with vegetables or ground meat or fish. They are fried until heated to the centre and stored in a hot cabinet until consumed.
Yoghurt is produced by fermenting milk using two species of bacteria that change milk sugar (lactose) into lactic acid. This forms the characteristic curd and restricts spoilage so that yoghurt is preserved for up to ten days in a refrigerator. Milk is a low acid food, which can contain food poisoning bacteria. It should be handled hygienically and kept cool until it is used. In the process milk is pasteurized and cooled to body temperature, and a starter culture of the bacteria is added. Either the starter can be bought as a powder or it can be taken from a previous batch of product. A simple incubator can be made using a block of thick polystyrene to hold the pots, which maintains the temperature of the product for several hours. Alternatively, pots are placed in an insulated box, fitted with an electric light bulb. The heat from the bulb maintains the temperature. Set yoghurt is made by filling pots with milk after adding the starter. For liquid yoghurt, the yoghurt is stirred to break the gel and then poured into pots. Chopped fruits or nuts can be added to each type of yoghurt, but care is needed to ensure that they are thoroughly cleaned to avoid contamination by moulds. Less acidic fruits such as melon or pawpaw are more successful because they do not react with the milk. Acidic fruits (lemon, lime, pineapple, etc.) may cause curdling and separation of the yoghurt.
