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Introduction main methods are:

drying curing (smoke or salt) canning & bottling pickling freezing

nutritional value is usually decreased - & also flavour, colour, aroma

use best available produce for preservation not the worst

see http://www.vita.org/pubs/docs/udc1.html and http://www.vita.org/pubs/docs/udc2.html alsohttp://www.unu.edu/unupress/unupbooks/80478e/80478E00.htm#Contents

Food preservation

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Canning / bottling heat to sterilise and exclude air sterilising by:

water bath pressure cooker - for low acid foods - achieves higher Ts

canning is most expensive method of preservation after freezing - energy requirements best method for long duration storage home canning may be less expensive than buying commercially canned produce water baths and pressure canners available commercially cost of labour should be included in analyses co-operatives?

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Freezing fruit not usually blanched or cooked before freezing

vegetables are blanched

freeze before packing together to prevent sticking

storage life of a year - write date

Asian Inst. of Tech. in Thailand have developed freezing unit that runs on solar energy

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Drying when 80 to 90% of water removed, cannot support microbial life

also salts, sugar, proteins increase their concentration - & also inhibit microbial reproduction

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3 methods: sun drying - no pre-treatment - dried in the open - long time- may become contaminated - sun-drying destroys some vitamins but weight for weight dried fruit is more nutritious than fresh

solar drying - dried in trays covered with glass or plastic - needs intense cloudless sunlight & dry air - 1 to 3 days

convection drying - 30° to 60°C optimum - fruit & veg retain more of vitamins - high cost of energy a problem

sun / solar drying the least expensive preservation methods

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improved drying of ingredients for preparation of Nepalese Gundruk - made from mustard, radish and cauliflower (!) make reduces loss of carotenoids & makes more nutritious

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Curing methods : -

salt (dry or as brine)

vinegar

oils

possibly combined with smoking to retard or prevent growth of micro-organisms

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Salting cured food - especially salted or brined food can store longer than dried food - vegetables, fish, cheese if sufficient moisture as in vegetables - can be dry salted - otherwise use brine draws out water and in high concentrations, inhibits micro-organisms; in smaller concentrations, salt promotes lactic acid producing bacteria - acidity eventually exceeds tolerance of bacteria including the lactic acid producers

Fermenting before salting• cabbage may be fermented - sauerkraut - before salting

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Pickling pickling - uses vinegar & spices instead of, or in addition to salt - e.g. fruit (mango pickle), onions, fish

Smoking smoking - mostly meat and fish - but sometimes vegetables tie to string and hang over an open fire or use a specially constructed smoke box - biltong some vegetables are salted, oiled, spiced before smoking

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Parboiling means to partly cook by boiling or steaming

mainly rice; in India > 50% of paddy is parboiled - soaking, steaming, then drying

modern Indian method utilises hot water for soaking at 70 to 80° C for 3.5 hours and eliminates the steaming process

main object of parboiling is to harden the grain and reduce milling losses

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parboiling also minimises losses during milling of thiamine, riboflavin, and niacin in rice grain -

during the parboiling process, water-soluble nutrients are driven from the outer layers into the inner layers of the grain and thus escape removal during milling

some sorghum varieties are soft, and respond well to parboiling for subsequent preparation of semolina

bulgur wheat represents a successful parboiling variety parboiling achieves case-hardening so is excellent method of treatment prior to storage (as well as prior to milling)

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Pasteurisation

Mainly for milk but pasteurisation helps shelf life ofother foods, e.g. of Kanji in N. India - made from carrots, salt, mustard seed & hot chilli

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Milling - flour flour can be made from any cereal and many root crops

in addition to milling to make flour, milling can also mean the removal of the coarse fibrous bran or the seed coat - especially rice - loses nutrient value (unless parboiled) though iron availability improves

roller mills most common

mix wheat flour with QPM (Quality Protein Maize) for compound

semolina is the left over hard bits - used directly or for pasta

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Baking - cakes and bread

mainly for town areas but village bakeries possible new approaches needed, e.g.:

in Jamaica, "Bammy bread" - round cakes soaked in coconut milk and grilled now being packaged, frozen and exported to Europe and North America cassava cheese bread in Brazil

Pasta & noodlesMade from wheat flour - good way of preserving wheat - easy to cook - used as staple in Italy - potential for other wheat growing areas such as India but people need to become familiar - needs marketing, etc.

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Chips and crisps produced in many countries including India, Kenya, etc mainly made and consumed in urban areas high income for farmers growing the special varieties needed in Colombia, improved technologies for producing cassava chips have been promoted to supply the expanding market for animal feed concentrates

Heat and serve preparation increasing trend - some being developed are based on cassava - but needs quite sophisticated equipment

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Vegetable oil extraction Africa imports large amounts of vegetable oil for cooking even though there is an immense capacity for local production

many designs exist, see e.g. http://www.attra.org/attra-pub/oilseed.html

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traditional Indian method = the ghani - now widespread elsewhere : -

wooden mortar and pestle; mortar is fixed to the ground, and the pestle located in mortar, raw material crushed by friction and pressure an animal is required to move the pestle oil pressed out & runs through hole at the bottom of the mortar residue (cake) scooped out two animals are required, since any one animal tires after 3-4 hours

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improved technologies for extracting oil include:

motorised ghanis

oil presses

oil expellers

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most oil presses work on a similar principle: raw materials are placed in heavy perforated or slotted metal cage and a metal plunger is used to press out the oil main differences in design are:

method used to move the plunger. amount of pressure in the press size of the cage plunger can be moved either manually or with the aid of a motor screw-thread or a hydraulic system

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oil presses can be manufactured locally: for a screw-press, however, a lathe is needed to manufacture the screw hydraulic presses may be manufactured locally if lorry jacks are available important that mineral oil used with either screw or hydraulic press does not contaminate the vegetable oil

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oil expellers - continual operation: use a horizontally-rotating screw which feeds oil-bearing raw material into barrel-shaped outer casing with perforated walls raw material is continuously fed to the expeller, which grinds, crushes, and presses out the oil as it passes through the machine oil flows through the perforations in the casing and is collected underneath residue, or oilcake, is pushed out of the end of the unit most small expellers are power-driven due to the wear and tear, screw needs to be repaired / replaced frequently - need skills and resources for maintenance to be available locally

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clarification: crude oil contains a suspension of fine pulp and fibre from plant material,

also contains smaller quantities of water, resins, colours, and bacteria which makes it dark in colour,

contaminants removed by clarifying the oil, either by allowing the oil to stand undisturbed for a few days & then removing the upper layer, or by using a clarifier

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if further clarification needed, oil may be filtered through a plastic funnel which has been fitted with a fine filter cloth,

oil is then heated to boil off traces of water and destroy any bacteria,

for raw materials which are processed wet (such ascoconut), heating is applied prior to clarification in order to break the emulsion

when these impurities are removed, the shelf-life of the oil is extended from a few days to several months, provided stored properly

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Germination and malting soaking in water overnight followed by germination or sprouting of the grain very common household practice, especially for pulses

several enzyme systems become active and bring about changes in the nutritive value of pulses: vitamin C, increases in significant amounts after germination as does folic acid in chick-pea and ragi

anti-nutritional factors such as phytate, trypsin inhibitor, and haemaglutinins are broken down on germination

pronounced reduction of phytate - organic acid which can lead to mineral deficiency - in both ragi (finger millet) and bajra (pearl millet)

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malting: grain spread in a thin layer and steeped in water so that it can germinate - germinated grain, which forms inside the husk, is called malt - dried and then cracked, liberating the malt from the husk

malted grain useful in making enzyme-rich flour as well as brewing

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Fermentation(see http://www.fao.org/docrep/x2184E/x2184e09.htm)

submerged fermentation - raw material submerged in water within a bioreactor or fermenting vat

solid substrate fermentation - food spread out over trays or leaves - uses less water

fermentation starters (prepared from the growth of moulds) on raw or cooked cereals is more commonly practised than using malted cereals

improved starter culture (e.g.) needed to accelerate speed of fermentation & to produce uniform end product in which losses of vitamins & other micronutrients minimised

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olive sediment, from traditional olive oil extraction mills was useless - now fermented product sufficiently digestible for use as animal feed

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Wine-making use of variety of fruit growing - buy when price low - for local consumption among neighbours or with better quality control - bottling and sale in local shops fruit wines such as papaya and banana wine now produced and sold commercially

Fruit juice see notes on processing of citrus juice expansion of Baobab fruit juice extract in Malawi - refreshing said to be a cure for hangovers - roadside extraction - keeps for 6 months - no special treatment

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Starch extraction from most cereals and many root crops widely used in producing glucose syrup, adhesives, paper, textiles, beer, pharmaceuticals, food, household textiles such as carpets, and rubber latex potential for export canna in Vietnam and sweet potatoes in China used as source of starch for transparent noodles (traditionally made from mungbean starch) - luxury food across Asia

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can be produced at village level - starch removed from plant by kneading with the hands or trampling by feet or, in more highly mechanised operations, by a spray of water; starch-laden water runs into a settling container

resulting starch "milk" contains starch in suspension and soluble solids in solution

starch is separated and washed free from the solubles, the water is removed (industrially by centrifugal action or in local methods it overflows - potential for water pollution a problem

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Jam and pectin production jam making not very common in rural areas of DCs because of large amounts of sugar - but popular in towns and cities - mainly made by medium sized operations pectin extracted from fruit for use in jam-making and in jellies and other foods many DCs import pectins even though great variety of natural perishable products that contain pectins, especially fruits wasted in great quantities - extractable from fruit “waste” extraction depends on pH, temperature and heating times and the quality of the fruits pectin now also made from cocoa waste

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Animal feedIncreasing potential as more livestock produced intensively, good income if near market - examples:

can use by-products from oil extraction such as groundnuts, sunflower dried cassava chips sliced fresh husks from cocoa used as a substitute for wheat bran to feed to pigs and rabbits.

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Papain from papaw latex obtained by making incisions on the surface of the green fruits early in the morning and repeating every 4 or 5 days until the latex ceases to flow

tool used has to be bone, glass, sharp-edged bamboo or stainless steel (knife or razor blade)

tappers hold coconut shell, clay cup, or glass, porcelain or enamel pan beneath the fruit to catch the latex, or a container like an "inverted umbrella" is clamped around the stem - latex coagulates quickly and is spread on fabric and oven-dried at a low temperature, then ground to powder and packed in tins (sun-drying tends to discolour)

tap 1,500 average-size fruits to harvest 1.5 lb papain

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used: as meat tenderiser (now even prior to slaughtering)

to clarify beer

to treat wool and silk before dyeing

to de-hair hides

in rubber manufacture

on tuna liver before extraction of the oil which is thereby made richer in vitamins A and D

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toothpastes, cosmetics and detergents, as well as pharmaceutical preparations to aid digestion

to treat ulcers

dissolve membranes in diphtheria

reduce swelling, fever and adhesions after surgery

applied on meat impacted in the gullet

injected in cases of slipped spinal discs or pinched nerves

NB - some individuals allergic to papain in any form and to meat tenderised with papain

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Soap and beauty products

potential for village based industry

e.g. fat extracted from cocoa beans from diseased pods or beans that have germinated during drying being used to make soap and pomade (cold cream) in W Africa