Traditional Food Preservation Techniques PDF

INTRODUCTION Food is composed of biochemical (chemical processes in living organisms) compounds derived from animals and plants. The major constituents of food are carbohydrates, proteins and fats while the minor constituents are the minerals, vitamins, enzymes, acids antioxidants (substance that s...

INTRODUCTION Food is composed of biochemical (chemical processes in living organisms) compounds derived from animals and plants. The major constituents of food are carbohydrates, proteins and fats while the minor constituents are the minerals, vitamins, enzymes, acids antioxidants (substance that slow/prevent oxidation of another chemical), pigments, flavour substances. Foods are subject to physical, chemical and biological deterioration. In this course we will study old-fashioned methods of preserving food. The major factors affecting food spoilage are: 1. Growth and activities of microorganisms (bacteria, yeast and moulds) 2. Activities of food enzymes (protein that catalyse chemical reactions) (and other chemical reactions within food itself 3. Infestation by insects and rodents 4. Inappropriate temperature for a given preserved food 5. Gain or loss of moisture 6. Reaction with oxygen 7. Light presence Vast majority of instances of food spoilage to one of the two major causes: 1. The attack by microorganism 2. Oxidation that causes destruction of essential biochemical compounds or destruction of plant and animal cells, there is adverse effect on appearance, flavour, texture, colour and nutritional values FOOD PRESERVATION DEFINITION Food preservation is the process of treating and handling food to stop or greatly slow down spoilage (loss of quality, edibility or nutritional values) caused or accelerated by microorganisms. Page 1 of 18  Preservation involves preventing growth of bacteria, fungi, other organisms, and retarding(delay) fat oxidation which cause rancidity (strong smell/taste). It involves inhibiting natural aging and colouration eg. Apple browning FOOD PRESERVATION HISTORY Food preservation had been followed in all cultures at different points in time. Man needed to survive, the preservation enabled man to form a community and consume food for survival. Different cultures used different methods of food preservation. Science entered new realms, discoveries, innovations of food preservation methods Tracing to history how the ancient cultures used to store and process items such as herbs, spices, meats, fruits and vegetables in the roman civilisation or ancient Egypt. The major milestone in food preservation history was in the 19th century. Till then, soldiers were living off preserved meats poorly cured and subject to spoilage, salt were the key preservative at that time. It was the French conqueror napoleon who started the search for better methods of preserving food by offering a vast sum of money to those who would devise safer and dependable methods of preserving food. It was the French chemist Nicholas Appert who came up with the solution; he found that sealing food in a container that was airtight could save food from rotting. Five decades later Frenchman Louis Pasteur discovered the link between presence of microorganisms and spoiling of food. Later more advanced methods followed. The astonishing fact about food preservation is that it permeated(passed)every culture at nearly every moment in time. To survive ancient man had to harness nature. In frozen climates he froze seal meat on the ice. In tropical climates he dried foods in the sun. Page 2 of 18 Food by its nature begins to spoil the moment it is harvested. Food preservation enabled ancient man to make roots and live in one place and form a community. He no longer had to consume the kill or harvest immediately, but could preserve some for later use. Each culture preserved their local food sources using the same basic methods of food preservation. Drying In ancient times the sun and wind would have naturally dried foods. Evidence shows that Middle East and oriental cultures actively dried foods as early as 12,000 B.C. in the hot sun. Later cultures left more evidence and each would have methods and materials to reflect their food supplies—fish, wild game, domestic animals, etc. Vegetables and fruits were also dried from the earliest times. The Romans were particularly fond of any dried fruit they could make. In the Middle Ages purposely built “still houses” were created to dry fruits, vegetables and herbs in areas that did not have enough strong sunlight for drying. A fire was used to create the heat needed to dry foods and in some cases smoking them as well. Freezing Freezing was an obvious preservation method to the appropriate climates. Any geographic area that had freezing temperatures for even part of a year made use of the temperature to preserve foods. Less than freezing temperatures were used to prolong storage times. Cellars, caves and cool streams were put to good use for that purpose. In America, estates had icehouses built to store ice and food on ice. Soon the “icehouse” became an “icebox”. In the 1800’s mechanical refrigeration was invented and was quickly put to use. Also in the late 1800’s Clarence Birdseye discovered that quick freezing at very low temperatures made for better tasting meats and vegetables. After some time he perfected his “quick freeze” process and revolutionized this method of food preservation. Page 3 of 18 Fermenting Fermentation was not invented, but rather discovered. No doubt that the first beer was discovered when a few grains of barley were left in the rain. Opportunistic microorganisms fermented the starch-derived sugars into alcohols. So too can be said about fruits fermented into wine, cabbage into Kim chi or sauerkraut, and so on. The skill of ancient peoples to observe, harness, and encourage these fermentations are admirable. Some anthropologists believe that mankind settled down from nomadic wanderers into farmers to grow barley to make beer in roughly 10,000 BC. Beer was nutritious and the alcohol was divine. It was treated as a gift from the gods. Fermentation was a valuable food preservation method. It not only could preserve foods, but it also created more nutritious foods and was used to create more palatable foods from less than desirable ingredients. Microorganisms responsible for fermentations can produce vitamins as they ferment. This produces a more nutritious end product from the ingredients. Pickling Pickling is preserving foods in vinegar (or other acid). Vinegar is produced from starches or sugars fermented first to alcohol and then the alcohol is oxidized by certain bacteria to acetic acid. Wines, beers and ciders are all routinely transformed into vinegars. Pickling may have originated when food was placed in wine or beer to preserve it, since both have a low pH. Perhaps the wine or beer went sour and the taste of the food in it was appealing. Containers had to be made of stoneware or glass, since the vinegar would dissolve the metal from pots. Never ones to waste anything our ancestors found uses for everything. The left over pickling brine found many uses. The Romans made a concentrated fish pickle sauce called “garum”. It was powerful stuff packing a lot of fish taste in a few drops. There was a spectacular increase in food preservation in the sixteenth century owing to the arrival in Europe of new foods. Ketchup was an oriental fish brine that traveled the spice route to Europe and eventually to America where someone Page 4 of 18 finally added sugar to it. Spices were added to these pickling sauces to make clever recipes. Soon chutneys, relishes, piccalillis, mustards, and ketchups were commonplace. Worcester sauce was an accident from a forgotten barrel of special relish. It aged for many years in the basement of the Lea and Perrins Chemist shop. Curing The earliest curing was actually dehydration. Early cultures used salt to help desiccate foods. Salting was common and even culinary by choosing raw salts from different sources (rock salt, sea salt, spiced salt, etc.). In the 1800’s it was discovered that certain sources of salt gave meat a red color instead of the usual unappetizing grey. Consumers overwhelmingly preferred the red colored meat. In this mixture of salts were nitrites (saltpeter). As the microbiology of Clostridium botulinum was elucidated in the 1920’s it was realized that nitrites inhibited this organism. Jam and Jelly Preservation with the use of honey or sugar was well known to the earliest cultures. Fruits kept in honey were commonplace. In ancient Greece quince was mixed with honey, dried somewhat and packed tightly into jars. The Romans improved on the method by cooking the quince and honey producing a solid texture. The same fervor of trading with India and the Orient that brought pickled foods to Europe brought sugar cane. In northern climates that do not have enough sunlight to successfully dry fruits housewives learned to make preserves—heating the fruit with sugar. Canning Canning is the process in which foods are placed in jars or cans and heated to a temperature that destroys microorganisms and inactivates enzymes. This heating Page 5 of 18 and later cooling forms a vacuum seal. The vacuum seal prevents other microorganisms from recontaminating the food within the jar or can. Canning is the newest of the food preservations methods being pioneered in the 1790s when a French confectioner, Nicolas Appert, discovered that the application of heat to food in sealed glass bottles preserved the food from deterioration. He theorized “if it works for wine, why not foods?” In about 1806 Appert's principles were successfully trialed by the French Navy on a wide range of foods including meat, vegetables, fruit and even milk. Based on Appert's methods Englishman, Peter Durand, used tin cans in 1810. Appert had found a new and successful method to preserve foods, but he did not fully understand it. It was thought that the exclusion of air was responsible for the preservations. It was not until 1864 when Louis Pasteur discovered the relationship between microorganisms and food spoilage/illness did it become clearer. Just prior to Pasteur’s discovery Raymond Chevalier-Appert patented the pressure retort (canner) in 1851 to can at temperatures higher than 212ºF. However, not until the 1920’s was the significance of this method known in relation to Clostridium botulinum. GENERAL PRINCIPLES OF TRADITIONAL FOOD PRESERVATION First we preserve food for the following reasons: 1. To take care of excess produce 2. To add food variety to our meals 3. For the food to reach areas where the food item hasn’t reached to 4. To make transportation easier(e.g. reduce bulk by drying leafy food) The general principles of traditional food preservation are: 1. Prevention and delay of microbial decomposition a) By keeping out microorganisms b) By removal of microorganisms Page 6 of 18  c) By hindering the growth and activity of microorganisms eg drying d) By killing microorganisms 2. Prevention or delay of self-decomposition of food a) By destruction or inactivation of food enzymes eg. Blanching b) By prevention and delay of chemical reactions eg using antioxidants METHODS OF TRADITIONAL FOOD PRESERVATION 1. FERMENTATION Fermentation Started 7000 years ago in Babylon, it started by mistake or accident. It was used out of preference or necessity DEFINITION OF FERMENTATION It is the controlled decay of material using special bacteria which produce more desirable product. TECHNICAL DEFINITION OF FERMENTATION Technically fermentation is the biochemical conversation of sugars, starches or carbohydrates into alcohol and organic acids by bacteria (yeast, mould etc) and enzymes under anaerobic condition. We have symbiotic relations with some bacteria, we give them what they need (carbohydrate) and they give us what we need (preserving acids COMMON GROUPS OF MICROORGANISMS USED IN FERMENTATION 1. BACTERIA (e.g. Lactobacillus which produce lactic acid from carbohydrates, aceto bacter producing acetic acid ) 2. YEAST ( Used in the leavening of bread, e.g. Saccharomyces) Page 7 of 18  3. MOULDS (used in the fermentation results of more than one microbes either working together or in sequence. Microorganisms play an important role in food industry. They are used in production of various food products, and are also responsible for food spoilage thereby causing intoxication and diseases. Microbial contamination of food products takes places usually on the way from the field to the processing plant, or during processing, storage, transport and distribution or before consumption. The microorganisms that cause food spoilage and also find the maximum exploitation in production of food and food products are mainly bacteria, molds and yeasts. Bacteria Bacteria are the largest group of unicellular microorganisms. The shapes of medically important bacteria are classified into-cocci, or spherical cells; bacilli, or cylindrical or rod shaped cells; and spiral or curved forms. The pathogenic or disease causing bacteria are usually gram negative, however, three gram-positive rods are known to cause food intoxications : Clostridium botulinum,C. perfringens,and Bacillus cereus Some of the other most common bacteria causing food spoilage, infections and disease are Acinetobacter, Aeromonas, Escherichia, Proteus, Alcaligenes, Flavobacterium, Pseudomonas, Arcobacter, Salmonella, Lactococcus, Serratia, Campylobacter, Shigella, Citrobacter, Listeria, Staphylococcus, Micrococcus, Corynebacterium, Vibrio Enterobacter, Paenibacillus, Weissella, Enterococcus, Yersinia Different strains of bacteria are also used in production of various food and dairy products. Strains of Streptococcus, Lactobacillus Bifidobacterium, Erwiniaetc. are used in the production of fermented food and dairy products. Streptococcus thermophilus and Lactobacillusbulgaricus are used to produce yogurt. Molds: Page 8 of 18 Molds are multicellular filamentous fungi whose growth on foods is usually readily recognized by their fuzzy or cottony appearance. They are mainly responsible for food spoilage at room temperature 25- 30C and low pH, and have minimum moisture requirement. Molds can rapidly grow on grains and corns when these products are stored under moist conditions. Molds require free oxygen for growth and hence grow on the surface of contaminated food. Molds also find their use in manufacturing of different foods and food products. They are used in ripening of various types of food products as cheese (e.g. Roquefort,Camembert). Molds are also grown as feed and food and are employed to produce ingredients such as enzymes like amylase used in making bread or citric acid used in soft drinks. Molds are major contributors in the ripening of many oriental foods. A species of Bothrytiscinerea, is used in rotting of grape for production of wine. Lactic fermentations using molds results in a unique Finnish fermented milk called viili. Yeasts: Yeasts have the ability to ferment sugars to ethanol and carbon-dioxide and hence they are extensively in food industry. The most commonly used yeast, the baker’s yeast is grown industrially. Saccharomyces carlsbergensis is most commonly used in fermentation of most beers. The other yeast strains of importance are Brettanomyces, Schizosaccharomyce,, Candida, Cryptococcus, Debaryomyces, Zygosaccharomyces, Hanseniaspora, Saccharomyces Points to remember Page 9 of 18   Bacteria, molds and yeast are the most important microorganisms that cause food spoilage and also find the maximum exploitation in production of food and food products.  Different strains of bacteria and fungus are used for fermentation of dairy products for production of a wide variety of cultured milk products. Both bacteria and fungi are used in these cheese production processes.  Lactic acid bacteria are used for coagulation of milk that can be processed to yield a wide variety of cheeses, including soft unripened, soft ripened, semisoft, hard, and very hard types.  Microorganisms such as Lactobacillus and Bifidobacterium are used as in food and health industry.  Spirulina, a cyanobacterium, also is a popular food source sold in specialty stores.  Molds are used for rotting of grapes for production of different varieties of wines.  Mushrooms (Agaricusbisporus) are one of the most important fungi used as a food source.  Alcoholic beverages as beer are produced by fermentation of cereals and grains using different strains of yeasts. Fermentation employed in food preservation is called Lacto-Fermentation to create Lactic acid in sour foods such as sauerkraut, yogurt or vinegar STEPS IN FERMENTATION a) Starter culture containing the preferred bacteria introduced to the food to be fermented can be done by adding small sampling from previous batch of converted food or commercially distributed one. Make sure the container is glass not plastic containing chemicals b) Cut the food to be fermented c) Salt the food or whey it d) Store the food Bread is raise by fermentation process. Yeast work, creates carbon dioxide (co2) gas doubling the food amount. The gas is burned during baking Page 10 of 18 Desirable bacteria cause less deterioration of food by inhibiting growth of spoiling types of bacteria. Some fermentation process lower ph of foods to be too acidic. Controlled fermentation encourages growth of good bacteria. Depending on what is fermented, or manner of fermentation food can remain consumable for a year. Fermentation can be stopped by means of heating and drying BENEFITS OF FERMENTATION a) Enhances flavour b) Makes food digestible c) Enhance nutritional values e.g. B-vit., enzyme, omega-3 fatty acid d) Suppresses helicobacter pylori ( gastrointestinal disease) 2. DRYING It is one of the oldest methods of preservation for the later use of food. It is simple, safe and learnable; it can be done at home. HOW DRYING PRESERVES FOOD Drying preserves food in the following ways: a) Drying removes moisture from food so bacteria, yeast and mould cannot grow. b) Drying slows down the action of enzymes Because drying removes moisture, food becomes smaller and lighter in weight. When food is ready for consumption then water is added and the food is back to its original shape. Food can be dried in the sun, oven or by dehydrators by using the right combination of warm temperature, low humidity and air current - Warm temperature cause moisture to evaporate Page 11 of 18  - Low Humidity allows moisture move quickly from food to the air - Air current speeds up drying by moving the surrounding moist air from the food. SUN DRYING Fruits are safe to be dried in the sun because of the below reasons: a) High sugar content b) Acid content Vegetables and meat are not recommended for sun drying because they are low in both sugar and acid content Meats are high in protein making them ideal for microbial growth when heat and humidity cannot be controlled in the sun drying. To dry in the sun, hot, dry, breezy days are the best; a minimum temperature of 860 F or 300 C is needed with higher temperature being better. It takes several days for food to dry because weather is uncontrollable. Sun drying is risky, high humidity is a problem, humidity below 60% is the best for sun drying, these ideal conditions mentioned are not available when fruits ripens. The fruits to be dried should be placed on trays made of wood and plastic. Avoid screens made of hardware cloth because they are coated with cadmium or zinc which can oxidize leaving harmful residues on food. Avoid copper and aluminium, copper destroys vitamin C while aluminium discolours and corrodes. The best trays to use when sun drying is wood, not green wood. When drying fruits, they have to be brought in at night. Page 12 of 18 3. PRESERVATION BY SALT AND SUGAR Preservation by salt (sodium chloride) and sugar (sucrose) protects food from microbial spoilage; foods going under this process are corned beef, bacon, pork, ham, fruits, and jams Salting and sugaring not only prevents food spoilage but inhibit or prevents growth of food borne diseases pathogens such as salmonella or clostridium botulinum WAYS HOW SALT AND SUGAR INHIBIT MICROBIAL GROWTH a) Osmosis Here water is moved out from the food preserved and salt and sugar molecules are inserted in the food resulting to reduction of product water activity (Aw). Aw of fresh food is 0.99, but 0.91 inhibits bacterial growth, moulds and yeast even require less Aw. Most disease-causing bacteria do not grow below 0.94 (10% sodium concentration). Most moulds grow at Aw 0.80 b) Interference Here the microbe’s activity is interfered to, leading to the weakening of the molecular structure of its DNA, sugar accelerates accumulation of anti bacterial growth e.g. Conversion of sugar to ethanol by yeast or conversation of sugar to organic acids, e.g. Lactic acid Microbes differ widely in their ability to resist salt or sugar. Other organisms grow at low Aw e.g. Halophiles (Salt-loving organisms) such as halobacillus and Halococcus. Sugar concentrated food (fruits) can be spoiled by sugar-loving yeast such as species of zygosaccharomyces Page 13 of 18 4. FOOD PRESERVATION BY CURING AND PICKLING (BRINING) A few words about salt Salt is essential to cured and pickled foods―to wilt the vegetables, inhibit bacterial growth, or to create the characteristic texture―so these items are naturally high in sodium. Curing, defined Curing is a method of preserving food (usually meat or fish) to prevent spoilage. Food can be cured by brining (soaking food in a saltwater solution), smoking, or salting (packing food in salt) ―we focus on salting here, which is easy to do at home. Curing has long been a way to make perishable, protein-rich foods last from barn to market, as in the case of bacon and prosciutto, or from shore to home, as in the case of salt cod or kippered herring. What salt-curing does The salt works on at least three fronts. First, it inhibits bacterial growth, thereby preserving foods like duck breasts or salmon for moderate lengths of time. That said, the salt doesn't inhibit all bacterial growth. Instead it allows for a moderate amount of fermentation―and thus the meat ends up with a mild, somewhat sweet twang, usually no more than a hint in the overall taste. Second, salt breaks down protein in muscle fibers so the meat or fish is more tender―as is evidenced in gravlax, corned beef brisket, or kosher chickens. Finally, salt can be used as a dehydrating agent, which creates dense and chewy but nonetheless tender meat or fish―the signature texture of ham, lox, or bacon. Best bets for curing In general, meat and fish are the best options, particularly those cuts and varieties that are relatively high in fat: brisket, duck, ham, and salmon, to name a few. Already-tender cuts or fillets like tenderloin or shrimp would gain little from the salt cure, no more than a strange aftertaste. Plus, these would quickly turn too soft from the salt's action. Page 14 of 18 Most vegetables benefit little from a salt cure―except for those with very high water concentrations like cabbage, cucumber, and eggplant. Once these foods are salted, they release much of their liquid and are then suitable for sauces, relishes, and the like. If not pre-salted, they would release liquid into the dish and water down the taste. Curing time Fish like salmon or halibut is cured for 24 to 48 hours, depending on how firm the flesh is. Meats like brisket or duck breasts are cured for longer periods; their muscular structures are more resilient to the salt's action. With meat, the larger the cut, the longer the cure. But timing is crucial. Too little time in the salt, and the fish or meat will not be adequately tenderized; too long, and the whole thing will turn unappealingly soft and mushy. So it's important to use the times specified in the recipes. Shelf life Because our home-cured meat and fish recipes use lower salt concentrations for a shorter time, and because they don't use nitrates (preservative chemical compounds used in many commercial products), they have a shorter shelf life than commercially cured foods. Nitrate-free cured meat or fish will last three to five days tightly covered in the refrigerator. Pickling, defined To pickle food is to preserve it by immersing it in a seasoned vinegar-based solution (often referred to as a brine). Flavors can be salty, sweet, or hot. What pickling does This technique encourages certain naturally occurring and harmless microbes to feed on the sugars produced as the food's proteins break down in the presence of salt. These microbes produce lactic acid, carbon dioxide, and even alcohol―compounds which in turn help preserve the food. Also, these helpful microbes leave most of the beneficial vitamins and minerals intact and further enhance the taste of the food preserved. In other words, the food is still nutritious and tasty weeks later. That's why it's a great way to preserve summer produce. Page 15 of 18 Best bets for pickling Sturdy vegetables work best―cabbage, cucumbers, olives, radishes, carrots, green beans, onions, and asparagus. Most fruits and many leafy greens simply wilt and break down too far. Pickling time Depending on the ingredients in the pickling liquid, food can be pickled in as little as a few hours or can take as long as a week or more. Both (curing and pickling) of the above mentioned methods serve: a) Enhancing meat and fish (flavour) b) Preserving food SALT Salt is very essential in curing and pickling foods, it does the following: a) Wilt vegetables b) Inhibit bacterial growth c) Create texture ( mouth feel ) CURING It is a method of preserving food such as meat and fish by salting, smoking and drying by preventing spoilage. Curing does the following: a) Inhibits bacterial growth b) It breaks down protein in muscle fibbers for tenderness c) It dehydrates food Foods to be cured are: meats, fish, brisket, duck, ham, salmon Page 16 of 18 Vegetables benefits little from salt-curing except for the high water concentration vegetables such as cabbage, cucumber and eggplant CURING TIME Salmon and halibut (fish) are cured for 24-48 hours depending on how firm the flesh is. Meat like brisket or duck breasts is cured for longer periods because their muscular structures are more resilient to salt action. The larger the cut the longer the curing process. Too little timing results to no good tenderness. Too long timing will lead to softness and mushiness. SHELF-LIFE For home nitrate-free cured food, it will last for only 3-5 days FOOD PICKLING Is a method of preserving food by immersing or dipping the food in a seasoned vinegar-based solution (brine) for its flavour to be salty, sweet or hot. Certain naturally occurring microbes are encouraged to feed on sugars produced as food breaks down in the presence of salt, these microbes produce lactic acid, and carbon dioxide and alcohol (ethanol) which in turn help preserve food. Also these microbes leave most beneficial vitamins and minerals and further enhance taste of the food preserved. Food is still nutritious and tasty weeks later. Food preserved by pickling are: sturdy vegetables such as cabbage, cucumber, olives, radishes, carrots, green beans, onions and asparagus PICKLING TIME Page 17 of 18 Depending on the ingredient, food can be pickle in a few hours or can take long as a week or more. SHELF-LIFE The pickled food should be kept in a refrigerator for weeks if possible and stored in non-reactive container such as glass or plastic. All vegetables submerged for freshness should be covered to avoid air entrance. When starting to consume the pickled food, change to a smaller container for cold storage. If some pickling solution lost, add little water to the solution SIMILARITIES BETWEEN FOOD CURING AND PICKLING a) Both of them are used for food preservation b) Both of them cure food c) Both use osmosis THE DIFFERENCES a) Curing is used mostly for preservation b) Pickling is mostly used as for flavouring c) Curing draws water out but pickling adds moisture d) Curing involves fish or while brining involves meat. References: https://nchfp.uga.edu/publications/nchfp/factsheets/food_pres_hist.html https://lab-training.com/2015/03/11/beneficial-role-of-microorganisms-in-food- industry/ https://www.cookinglight.com/cooking-101/techniques/cooking-class-curing- pickling Page 18 of 18