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Food is any substance that can be consumed for nutritional value and to provide extra energy. Food is the main source of energy and of nutrition for animals, and is usually of animal or plant origin. Many countries have a recognizable cuisine, a specific set of cooking traditions and practices. Humans are omnivorous animals that can consume both plant and animal products. Evidence suggests that early humans employed hunter-gatherer techniques as their primary method of food collection. This involves .bining stationary plant and fungal food sources (such as fruits, grains, roots, and mushrooms) with mobile animals which must be hunted and killed in order to be consumed. Additionally, it is believed that humans have used fire to prepare food prior to eating since their divergence from Homo erectus, possibly even earlier. At least ten thousand years ago, humans developed agriculture, which has altered the kind of food people eat. This led to a variety of important historical consequences, such as increased population, the development of cities, and the wider spread of infectious diseases. The types of food consumed, and the way in which they are prepared, have varied widely by time, location, and culture. Meals A portion of food or the act of eating a portion of food is considered a meal. Often named and patterned, meals play a role in an important social occasion, such as the celebration of many key cultural and religious festivals. A meal can be used as means for feeding a single individual or shared and eaten simultaneously by two or more people. The number of meals consumed by individuals in a day, their size, .position, when and how they are prepared and eaten varies greatly around the world. This diversity can be attributed to a number of local factors, including climate, ecology, economy, cultural traditions and industrialisation. In societies where the availability of food has risen above subsistence levels and beyond staple foods, meals are also sold pre-prepared for immediate consumption in restaurants and other similar retail premises. Food eaten in smaller quantities between the culturally normative meals is regarded as snack food. Food preparation While some food can be eaten without preparation, many foods undergo some form of preparation for reasons of safety, palatability, or flavor. At the simplest level this may involve washing, cutting, trimming or adding other foods or ingredients, such as spices. It may also involve mixing, heating or cooling, pressure cooking, fermentation, or .bination with other food. Most food preparation takes place in a kitchen. The preparation of animal-based food will usually involve slaughter, evisceration, hanging, portioning and rendering. Food manufacture Early food processing techniques were limited by the available food preservation, packaging and transportation. Early food processing mainly involved salting, curing, curdling, drying, pickling and smoking. An early processed food product was cheese. During the industrialisation era in the 19th century, food manufacturing arose. This development took advantage of new mass markets and emerging new technology, such as milling, preservation, packaging and labelling and transportation. It brought the advantages of pre-prepared time saving food to the bulk of ordinary people who did not employ domestic servants. At the start of the 21st century, a two-tier structure has arisen, with a few international food processing giants controlling a wide range of well known food brands; with a populous number of small local or national food processing .panies. Food safety Foodborne illness, .monly called "food poisoning," is caused by bacteria, toxins, viruses and prions. Food poisoning has been recognised as a disease of man since as early as Hippocrates. Murder by food poisoning was used during the Roman Empire. In the Middle Ages all Royal Courts had food tasters. The sale of rancid, contaminated or adulterated food was .monplace until introduction of hygiene, refrigeration, and vermin controls in the 19th century. Discovery of techniques for killing bacteria using heat and other microbiological studies by scientists such as Louis Pasteur contributed to the modern sanitation standards that we enjoy today. This was further underpinned by the work of Justus von Liebig whose work led to the development of modern food storage and food preservation methods. The two most .mon factors leading to cases of bacterial foodborne illness are cross-contamination of ready-to-eat food from other uncooked foods and improper temperature control. Less .monly, acute adverse reactions can also occur if chemical contamination of food occurs, for example from improper storage, or use of non-food grade soaps and disinfectants. Food can also be adulterated by a very wide range of articles (known as ‘foreign bodies’) during farming, manufacture, cooking, packaging, distribution or sale. For example, pests (or their feces), hairs, cigarette butts, wood chips, metal shards, plasters etc. It is possible for certain types of food to be.e contaminated if stored or presented in an unsafe container, such as a ceramic pot with lead-based glaze. Understanding of the causes of food-borne-illnesses and more systematic techniques for their elimination has led to the development of .mercial systems such as HACCP which can, if properly implemented, identify and eliminate many, but not all, possible risks. HACCP is well suited to identifying and controlling these potential food safety risks. Food allergies Some people have food allergies or sensitivities to foods which are otherwise wholesome to the majority of people. The amount of the food substance required to provoke a reaction in a susceptible individual can be minute. For instance, tiny amounts of food in the air, too minute to be smelled, have been known to provoke lethal reactions in sufficiently sensitive individuals. In theory, any food may provoke a reaction, however, this most .monly involves gluten, corn, shellfish (mollusks), peanuts, and soy. Most patients present with diarrhea after ingesting certain foodstuffs, skin symptoms (rashes), bloating, vomiting and regurgitation. The digestive .plaints usually develop within half an hour of ingesting the allergen. Rarely, food allergy can lead to anaphylactic shock: hypotension (low blood pressure) and loss of consciousness. This is a medical emergency. An allergen associated with this type of reaction is peanut, although latex products can induce similar reactions. Initial treatment is with epinephrine (adrenaline), often carried by known patients in the form of an Epi-pen. Food allergy is thought to develop easier in patients with the atopic syndrome, a very .mon .bination of diseases: allergic rhinitis and conjunctivitis, eczema and asthma. The syndrome has a strong inherited .ponent; a family history of these diseases can be indicative of the atopic syndrome. 相关的主题文章: