Introduction main methods are: drying curing (smoke or salt) canning & bottling

Food preservation • 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 also http://www.unu.edu/unupress/unupbooks/80478e/80478E00.htm#Contents

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?

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

Drying • when 80 to 90% of water removed, cannot support microbial life • also salts, sugar, proteins increase their concentration - & also inhibit microbial reproduction

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

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

Curing • methods : - • salt (dry or as brine) • vinegar • oils • possibly combined with smoking to retard or prevent growth of micro-organisms

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

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

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

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)

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

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

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 & noodles Made 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.

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

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

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

improved technologies for extracting oil include: • motorised ghanis • oil presses • oil expellers

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

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

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

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

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 as coconut), 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

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)

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

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

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

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

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

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

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

Animal feed • Increasing 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.

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

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

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

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

Introduction main methods are: drying curing (smoke or salt) canning & bottling