A raisin is a dried grape. Raisins are produced in many regions of the world and may be eaten raw or used in cooking, baking, and brewing. In the United Kingdom, Ireland, New Zealand, and Australia, the word raisin is reserved for the dark-colored dried large grape,[1] with sultana being a golden-colored dried grape, and currant being a dried small Black Corinth seedless[2] grape.[3]

A variety of raisins from different grapes
Golden raisins (sultanas)

EtymologyEdit

The word "raisin" dates back to Middle English and is a loanword from Old French; in modern French, raisin means "grape", while a dried grape is a raisin sec, or "dry grape". The Old French word, in turn, developed from the Latin word racemus, "a bunch of grapes".[4]

VarietiesEdit

 
California seedless grape raisins on the left and California Zante currants on the right, along with a metric ruler for scale.

Raisin varieties depend on the type of grape used and are made in a variety of sizes and colors including green, black, brown, blue, purple, and yellow. Seedless varieties include the sultana (the common American type is known as Thompson Seedless in the United States), the Greek currants (black corinthian raisins, Vitis vinifera L. var. Apyrena)[2] and Flame grapes. Raisins are traditionally sun-dried, but may also be water-dipped and artificially dehydrated.

"Golden raisins" are generally dried in dehydrators with controlled temperature and humidity, which allows them to retain a lighter color and more moisture. They are often treated with sulfur dioxide after drying.

Black Corinth or Zante currant are miniature, sometimes seedless[2] raisins that are much darker and have a tart, tangy flavor. They are often called currants. Muscat raisins are large compared to other varieties, and also sweeter.

Several varieties of raisins produced in Asia are available in the West only at ethnic grocers. Monukka grapes are used for some of these.[5]

Raisin processing and productionEdit

Raisins are produced commercially by drying harvested grape berries. For a grape berry to dry, water inside the grape must be removed completely from the interior of the cells onto the surface of the grape where the water droplets can evaporate.[6] However, this diffusion process is very difficult because the grape skin contains wax in its cuticle, which prevents the water from passing through.[6] In addition to this, the physical and chemical mechanisms located on the outer layers of the grape are adapted to prevent water loss.[7] The three steps to commercial raisin production include pre-treatment, drying, and post-drying processes.[6]

Pre-treatmentEdit

Pre-treatment is a necessary step in raisin production to ensure the increased rate of water removal during the drying process.[6] A faster water removal rate decreases the rate of browning and helps to produce more desirable raisins.[6] The historical method of completing this process was developed in the Mediterranean and Asia Minor areas by using a dry emulsion cold dip made of potassium carbonate and ethyl esters of fatty acids.[7] This dip was shown to increase the rate of water loss by two- to three-fold.[7]

Recently, new methods have been developed such as exposing the grapes to oil emulsions or dilute alkaline solutions. These methods can encourage water transfer to the outer surface of grapes which helps to increase the efficiency of the drying process.[6]

Raisins, seedless
Nutritional value per 100 g (3.5 oz)
Energy299 kcal (1,250 kJ)
79.3 g
Sugars65.2 g
Dietary fiber4.5 g
0.25 g
3.3 g
VitaminsQuantity %DV
Thiamine (B1)
9%
0.106 mg
Riboflavin (B2)
10%
0.125 mg
Niacin (B3)
5%
0.766 mg
Pantothenic acid (B5)
2%
0.095 mg
Vitamin B6
13%
0.174 mg
Folate (B9)
1%
5 μg
Choline
2%
11.1 mg
Vitamin C
3%
2.3 mg
Vitamin E
1%
0.12 mg
Vitamin K
3%
3.5 μg
MineralsQuantity %DV
Calcium
6%
62 mg
Copper
14%
0.27 mg
Iron
14%
1.8 mg
Magnesium
10%
36 mg
Phosphorus
14%
98 mg
Potassium
16%
744 mg
Selenium
1%
0.6 μg
Sodium
2%
26 mg
Zinc
4%
0.36 mg
Other constituentsQuantity
Water15.5 g

Percentages are roughly approximated using US recommendations for adults.
Source: USDA FoodData Central

DryingEdit

The three types of drying methods are: sun drying, shade drying, and mechanical drying.[6][further explanation needed] Sun drying is an inexpensive process; however, environmental contamination, insect infections, and microbial deterioration can occur and the resulting raisins are often of low quality. Additionally, sun drying is a very slow process and may not produce the most desirable raisins.[6]

Mechanical drying can be done in a safer and more controlled environment where rapid drying is guaranteed. One type of mechanical drying is to use microwave heating. Water molecules in the grapes absorb microwave energy resulting in rapid evaporation. Microwave heating often produces puffy raisins.[6]

Post-drying processesEdit

After the drying process is complete, raisins are sent to processing plants where they are cleaned with water to remove any foreign objects that may have become embedded during the drying process.[6] Stems and off-grade raisins are also removed. The washing process may cause rehydration, so another drying step is completed after washing to ensure that the added moisture has been removed.[6]

All steps in the production of raisins are very important in determining the quality of raisins. Sometimes, sulfur dioxide is applied to raisins after the pre treatment step and before drying to decrease the rate of browning caused by the reaction between polyphenol oxidase and phenolic compounds. Sulfur dioxide also helps to preserve flavor and prevent the loss of certain vitamins during the drying process.[7]

ProductionEdit

Global production of raisins in 2016 was 1.2 million metric tons, with the US as the top producer contributing 24% of the global harvest.[8]

NutritionEdit

Raisins are 15% water, 79% carbohydrates (including 4% fiber), 3% protein, and contain negligible fat (table). In a 100 gram reference amount, raisins supply 299 kilocalories and moderate amounts (10-19% DV) of the Daily Value for several dietary minerals, riboflavin, and vitamin B6 (table).

Toxicity in animalsEdit

Raisins can cause kidney failure in dogs. The cause of this is not known.[9]

GalleryEdit

See alsoEdit

ReferencesEdit

  1. ^ Dom Costello. "Kew Gardens explanation". Royal Botanic Gardens, Kew. Archived from the original on 5 September 2012. Retrieved 16 January 2013.
  2. ^ a b c Chiou, Antonia; Panagopoulou, Eirini A.; Gatzali, Fotini; De Marchi, Stephania; Karathanos, Vaios T. (2014). "Anthocyanins content and antioxidant capacity of Corinthian currants (Vitis vinifera L., var. Apyrena)". Food Chemistry. 146: 157–65. doi:10.1016/j.foodchem.2013.09.062. PMID 24176327.
  3. ^ "currant". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.) Entry at "currant": "'raisins of Corauntz n.' (also called 'raisins of Corinth')".
  4. ^ Harper, Douglas. "raisin". Online Etymology Dictionary.
  5. ^ "Types of Raisins: Currants, Golden Seedless, and More". Berkeley Wellness. Remedy Health Media. Archived from the original on 21 September 2017. Retrieved 20 September 2017.
  6. ^ a b c d e f g h i j k Esmaiili, M.; Sotudeh-Gharebagh, R.; Cronin, K.; Mousavi, M. A. E.; Rezazadeh, G. (2007). "Grape Drying: A Review". Food Reviews International. 23 (3): 257. doi:10.1080/87559120701418335. S2CID 83652015.
  7. ^ a b c d Christensen, L.P., and Peacock, W.L. (20 April 2013) "The Raisin Drying Process" Archived 12 June 2013 at the Wayback Machine. Raisin Production Manual, University of California at Davis.
  8. ^ "Nuts & Dried Fruits Global Statistical Review 2015 / 2016, p 66" (PDF). International Nut and Dried Fruit Council. Archived from the original (PDF) on 16 May 2017. Retrieved 26 June 2017.
  9. ^ DiBartola, Stephen P. (2012). Fluid, electrolyte, and acid-base disorders in small animal practice (4th ed.). St. Louis, Mo.: Saunders/Elsevier. p. 155. ISBN 978-1-4377-0654-3.