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Dried fruit is fruit from which the majority of the original water content has been removed either naturally, through sun drying, or through the use of specialized dryers or dehydrators. Dried fruit has a long tradition of use dating back to the fourth millennium BC in Mesopotamia, and is prized because of its sweet taste, nutritive value, and long shelf life.
Today, dried fruit consumption is widespread. Nearly half of the dried fruits sold are raisins, followed by dates, prunes, figs, apricots, peaches, apples and pears. These are referred to as "conventional" or "traditional" dried fruits: fruits that have been dried in the sun or in heated wind tunnel dryers. Many fruits such as cranberries, blueberries, cherries, strawberries and mango are infused with a sweetener (e.g. sucrose syrup) prior to drying. Some products sold as dried fruit, like papaya, kiwi fruit and pineapple are most often candied fruit.
Dried fruits retain most of the nutritional value of fresh fruits. The specific nutrient content of the different dried fruits reflects their fresh counterpart and the processing method. In general, all dried fruits provide essential nutrients and an array of health protective bioactive ingredients, making them valuable tools to both increase diet quality and help reduce the risk of chronic disease.
Traditional dried fruit such as raisins, figs, dates, apricots and apples have been a staple of Mediterranean diets for millennia. This is due partly to their early cultivation in the Middle Eastern region known as the Fertile Crescent, made up by parts of modern Iraq, Iran and Syria, southwest Turkey and northern Egypt. Drying or dehydration also happened to be the earliest form of food preservation: grapes, dates and figs that fell from the tree or vine would dry in the hot sun. Early hunter-gatherers observed that these fallen fruit took on an edible form, and valued them for their stability as well as their concentrated sweetness.
The earliest recorded mention of dried fruits can be found in Mesopotamian tablets dating to about 1700 BC, which contain what are probably the oldest known written recipes. These clay slabs, written in Akkadian, the daily language of Babylonia, were inscribed in cuneiform and tell of diets based on grains (barley, millet, wheat), vegetables and fruits such as dates, figs, apples, pomegranates, and grapes. These early civilizations used dates, date juice evaporated into syrup and raisins as sweeteners. They included dried fruits in their breads for which they had more than 300 recipes, from simple barley bread for the workers to very elaborate, spiced cakes with honey for the palaces and temples. Because cuneiform was very complex and only scribes who had studied for years could read it, it is unlikely that the tablets were meant for everyday cooks or chefs. Instead they were written to document the culinary art of the times. Many recipes are quite elaborate and have rare ingredients so we may assume that they represent "Mediterranean haute cuisine".
The date palm was one of the first cultivated trees. It was domesticated in Mesopotamia more than 5,000 years ago. It grew abundantly in the Fertile Crescent and it was so productive (an average date palm produces 50 kg (100 lbs) of fruit a year for 60 years or more) that dates were the cheapest of staple foods. Because they were so valuable they were well recorded in Assyrian and Babylonian monuments and temples. The villagers in Mesopotamia dried them and ate them as sweets. Whether fresh, soft-dried or hard-dried, they helped to give character to meat dishes and grain pies. They were valued by travelers for their energy and were recommended as stimulants against fatigue.
Figs were also prized in early Mesopotamia, Israel and Egypt where their daily use was probably greater than or equal to that of dates. As well as appearing in wall paintings, many specimens have been found in Egyptian tombs as funerary offerings. In Greece and Crete, figs grew very readily and they were the staple of poor and rich alike, particularly in their dried form.
Grape cultivation first began in Armenia and the eastern regions of the Mediterranean in the 4th century BC. Here, raisins were manufactured by burying grapes in the desert sun. Very quickly, viticulture and raisin production spread across northern Africa including Morocco and Tunisia. The Phoenicians and the Egyptians popularized the production of raisins, probably due to the perfect environment for sun drying. They put them in jars for storage and allotted them to the different temples by the thousands. They also included them in their breads and their various pastries, some made with honey, some with milk and eggs.
From the Middle East, these fruits spread through Greece to Italy where they became a major part of the diet. Ancient Romans ate raisins in spectacular quantities and all levels of society, including them as a key part of their common meals, along with olives and fruits. Raisined breads were common for breakfast and were consumed with their grains, beans and cultured milks. Raisins were so valued that they transcended the food realm and became rewards for successful athletes as well as premium barter currency.
Having dried fruits was a must in ancient Rome as these instructions for housekeepers around 100 BC tell: "She must keep a supply of cooked food on hand for you and the servants. She must keep many hens and have plenty of eggs. She must have a large store of dried pears, sorbs, figs, raisins, sorbs in must, preserved pears and grapes and quinces. She must also keep preserved grapes in grape-pulp and in pots buried in the ground, as well as fresh Praenestine nuts kept in the same way, and Scantian quinces in jars, and other fruits that are usually preserved, as well as wild fruits. All these she must store away diligently every year."
Figs again were extremely popular in Rome. Dried figs were equated with bread and formed a major part of the winter food of country people. They were rubbed with spices such as cumin, anise and fennel seeds, or toasted sesame, wrapped in fig leaves and stored in jars.
Plums, apricots and peaches had their origins in Asia. They were domesticated in China in the 3rd millennium BC and spread to the Fertile Crescent where they were also very popular, fresh and dried alike. They arrived in Greece and Italy much later and were very expensive but valued in the preparation of gourmet dishes with port or stewed with honey and spices.
Today, dried fruit is produced in most regions of the world, and consumption occurs in all cultures and demographic segments. In the United States, Americans consumed an average of 2.18 lb (1 kg) (processed weight) of dried fruit in 2006. Raisins accounted for about two thirds of this. California produces the largest percentage of the US and the world's dried fruit crop. It accounts for over 99% of the US crop of raisins and dried plums, 98% of dried figs, 96% of dried peaches, 92% of apricots and over 90% of dates. Most of California dried fruit production is centered in the San Joaquin Valley where the soil and climate, especially the hot, dry summers, provide ideal growing conditions. While these fruits were commonly dried in the sun in the past, now only raisins are almost entirely naturally sun-dried.
Fruits can be dried whole (e.g., grapes, berries, apricot, plum), in halves, or as slices, (e.g., mango, papaya, kiwi). Alternatively they can be chopped after drying (e.g., dates), made into pastes, or concentrated juices. The residual moisture content can vary from small (3 – 8%) to substantial (16 – 18%), depending on the type of fruit. Fruits can also be dried in puree form, as leather, or as a powder, by spray of drum drying. They can be freeze dried. Fresh fruit is frozen and placed in a drying chamber under vacuum. Heat is applied and water evaporates from the fruit while still frozen". The fruit becomes very light and crispy and retains much of its original flavor. Dried fruit is widely used by the confectionery, baking, and sweets industries. Food manufacturing plants use dried fruits in various sauces, soups, marinades, garnishes, puddings, and food for infants and children.
As ingredients in prepared food, dried fruit juices, purées and pastes impart sensory and functional characteristics to recipes:
- The high fiber content provides water absorbing and water binding capabilities, tenderization and nutritional enhancement.
- Organic acids such as sorbitol act as humectants, provide dough and batter stability, and control of water activity.
- Fruit sugars add sweetness, humectancy, surface browning and control water activity.
- Fruit acids, such as malic acid and tartaric acid, contribute to flavor enhancement and act as anti-microbial agents (suppress mold and bacterial growth).
- Vitamins and minerals increase nutritional value and label appeal.
- Phenolic compounds slow down lipid oxidation in meats. They add a natural caramel color.
The high drying and processing temperatures, the intrinsic low pH of the fruit, the low water activity (moisture content) and the presence of natural antimicrobial compounds in dried fruit make them a remarkably stable food. There is no known incident of a food-borne illness related to dried fruit.
Sulfur dioxide is used as an antioxidant in some dried fruits to protect their color and flavor. For example, in golden raisins, dried peaches, apples and apricots sulfur dioxide is used to keep them from losing their light color by blocking browning reactions that darken fruit and alter their flavor. Over the years, sulfur dioxide and sulfites have been used by many populations for a variety of purposes. Sulfur dioxide was first employed as a food additive in 1664, and was later approved for such use in the United States as far back as the 1800s.
Sulfur dioxide, while harmless to healthy individuals, can induce asthma when inhaled or ingested by sensitive people. The Food and Drug Administration (FDA) estimates that one out of a hundred people is sulfite-sensitive (allergic), and about 5% of asthmatics are also at risk of suffering an adverse reaction. Given that about 10% of the population suffers from asthma, this figure translates to 0.5% of the whole population with potential for sulfite-sensitivity. These individuals make up the subgroup of greatest concern and are largely aware of the need to avoid sulfite-containing foods. Consequently, the FDA requires food manufactures and processors to disclose the presence of sulfiting agents in concentrations of at least 10 parts per million.
In Taipei, Taiwan, a 2010 city health survey found one-third of tested dried fruit products failed health standard tests, most having excessive amounts of sodium cyclamate, some at levels 20 times higher than the legal limit.
Dried fruits retain most of the nutritional value of fresh fruits, and so are included with fresh fruit in dietary recommendations by U.S. and world health agencies. The specific nutrient content of the different dried fruits reflect their fresh counterpart and the processing method (e.g., traditional dried fruits versus sugar infused dried fruit). In general, all dried fruits provide essential nutrients and an array of health protective bioactive ingredients, making them valuable tools to both increase diet quality and help reduce the risk of chronic disease. The combination of nutritional value and enjoyable taste is the reason dried fruits have been popularly considered a healthy food for millennia. Because they are naturally resistant to spoilage, easy to store and transport and relatively low in cost, dried fruits are a convenient way to increase the number of servings of fruit in the diet. The following are basic nutritional facts on dried fruits:
- Like fresh fruits, dried fruits have very low sodium content.
- Dried fruits are a particularly significant source of dietary fiber and potassium. On a per serving basis (1/4 cup) dried fruits are among the top 50 contributors of these nutrients among all foods in the American diet. Amongst all fruits, they are among the top 5 contributors of potassium and fiber.
- Dried fruits also provide essential nutrients that are otherwise low in today's diets, such as vitamin A (apricots and peaches), calcium (figs), vitamin K (dried plums), iron, and copper. Raisins and dried plums are among the 50 major contributors of boron in the American diet raisins having the highest concentration at 2.2 mg per 100 g. Boron, a putative trace element is important for the growth and maintenance of healthy bones and joints.
- Traditional dried fruits have no added sugars. Drying removes some of the fruits' water and so concentrates their natural sugars. This, however, is normalized by a smaller serving size (e.g. 40 g for raisins versus 126 g for grapes, Nutrition Labeling and Education Act). For this reason, total sugar and energy values are similar between dried and fresh fruit. Most traditional dried fruits have minimal amounts of sucrose, their sugar is in the form of fructose and glucose.
The following are some of these health protective components in dried fruits:
- Dried fruits are an excellent source of polyphenols and phenolic acids. These compounds make up the largest group of phytochemicals in the diet and appear to be, at least in part, responsible for the potential benefit associated with the consumption of diets abundant in fruits and vegetables. Different dried fruits have unique phenolic profiles. For example, the most abundant in raisins are the flavonols quercetin and kaempferol and the phenolic acids caftaric and coutaric acid. Dates contain quercetin, apigenin and luteolin; dried plums are very high in chlorogenic and neochlorogenic acids; cranberries and blueberries are high in anthocyanins and anthocyanidins.
- By virtue of their high polyphenol content, dried fruits are an important source of antioxidants in the diet. These phytochemicals are believed to account for a major portion of antioxidant capacity in plant foods. Antioxidants can lower oxidative stress and so prevent oxidative damage to critical cellular components. Dried apricots and peaches are also important sources of carotenoids. These compounds not only are precursors of vitamin A but they also have antioxidant activity.
- Dried fruits such as dried plums provide pectin, a soluble fiber that may lower blood cholesterol levels.
- Dried fruits such as raisins are a source of prebiotic compounds in the diet. They contain fructooligosacharides like inulin, naturally occurring fiber-like carbohydrates that contribute to colon health.
- Dried fruits contain organic acids such as tartaric acid (raisins) and sorbitol (dried plums). These organic acids and fiber appear to work synergistically to maintain a healthy digestive system. They may also help increase the bioavailability of minerals in the diet, such as calcium and iron.
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Traditional dried fruit have a low to moderate Glycemic Index (GI) – a measure of how a food affects blood sugar levels. GI measures an individual's response to eating a carbohydrate-containing food (usually 50 grams of available carbohydrates) compared to the individual's response to the same amount of carbohydrates from either white bread or glucose. Carbohydrate containing foods are classified as high (above 70), moderate (56–69), or low (0–55) GI. Foods with high fiber content generally have a low GI. However, other factors also contribute to a food's glycemic response, such as the type of carbohydrate or sugar present, the physical characteristic of the food matrix and the presence of organic acids. All studies assessing the GI of dried fruit show that they are low to moderate GI foods and that the insulin response is proportional to their GI. Factors thought to contribute to this glycemic response include the viscous texture of dried fruits when chewed; their whole food matrix; the presence of phenolic compounds and organic acids and the type of sugar present (about 50% fructose in most traditional dried fruit).
The predominant sugars in traditional dried fruit are fructose and glucose, with trace amounts of sucrose. It is sucrose that serves as a substrate for the synthesis of adherent compounds in dental plaque, the causal agent in tooth decay and gum disease. Studies comparing the cariogenicity of different sugars (sucrose, maltose, lactose, fructose and glucose) invariably demonstrate that sucrose, more than any other type of sugar, induces the most smooth-surface-type and fissure-type caries.
Dried fruits, particularly dried plums, may promote bone health. Research conducted with dried plums indicates that they have a role in supporting bone health. This may be because they are rich in phenolic compounds, such as phenolic acids and lignans, which may stimulate bone formation and enhance osteoblast activity. Animal studies have shown that dried plums protect, and even reverse, bone loss in models of osteopemia (low bone mineral density, a precursor to osteoporosis). For example, feeding dried plums reduced loss of bone in ovariectomized rats in a dose-dependent fashion. It also increased circulating insulin-like growth factor (IGF-1). Serum IGF-1 is known to stimulate bone formation, osteoblast activity, and collagen synthesis and has a role in bone remodeling. A follow-up study showed that dried plums restored loss of tibial and femoral density in an osteopenic rat model of osteoporosis. Various doses of dried plums were also able to significantly improve trabecular bone structure and increase tibial bone volume and connectivity. These observations are unique because it is believed that once bone volume and connectivity are lost they cannot be brought back to normal. In studies where bone loss was produced by skeletal unloading, a diet containing dried plums also enhanced bone recovery by increasing bone mineral density and trabecular bone structure. The effect was similar to parathyroid hormone treatment.
In vitro studies have shown that dried plum polyphenols suppress osteoclast differentiation and activity under normal, oxidative stress and inflammatory conditions. These studies also show that dried plum enhances osteoblast ALP activity, calcified nodule formation and type I collagen cross-linking. These changes may be mediated by up regulating transcription and growth factors. In addition to animal studies, the findings of a short-term (three month) clinical trial showed that the consumption of dried plums (100 grams per day) by postmenopausal women significantly increased markers of bone formation including serum total alkaline phosphatase (ALP) activity, bone-specific ALP activity and IGF-1. Currently, a one-year comparative control randomized study is being conducted to confirm these findings and to determine whether dried plum increases bone mass or prevents further bone loss in osteopemic postmenopausal women. While the mechanism of action of dried plums remains to be elucidated, researchers believe that phenolic compounds may be the major bone protective agents. However, essential nutrients like vitamin K and minerals like potassium and the trace element boron may contribute to their beneficial effect. Dried plums are also high in copper, which is essential for bone building processes as it is a co-factor of lysyl oxidase. This enzyme promotes cross-linking of lysine residues in collagen and elastin.
Dried fruits promote digestive health. There is considerable research supporting the role of dried fruit in regulating bowel function and maintaining a healthy digestive system. Dried plums are well known in common experience to alleviate constipation. Some researchers ascribe it to their high fiber content: the combination of soluble (49%) and insoluble fiber (51%) in dried plums probably acts in a gentle way in the lower intestines, softening stool increasing bulk and promoting intestinal motility. More recent research indicates that they also provide prebiotic compounds such as fructans, which help to maintain intestinal balance and colonic health.
Dried fruits may contribute to healthy body weights. Emerging data suggests that dried fruit intake is not associated with higher body weight. On the contrary, recent analysis of NHANES (1999–2004) data indicates that diets high in dried fruits are associated with lower Body Mass Index (BMI), reduced overweight and obesity and improved diet quality. Moreover, after adjusting for potential confounders (socioeconomic status, education, exercise), these data show that prevalence of overweight/obesity and prevalence of abdominal obesity are lower for those who consume dried fruits than for those who did not. Finally, emerging data suggest that dried fruit promotes satiety by affecting the levels of hormones such as leptin that regulate appetite.
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- California Dates Administrative Committee http://www.datesaregreat.com
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