Глобално: Зошто компирот со висок принос може да изгуби вредност — потемнувањето по готвењето расте во складирањето
Клучни преземања
- 2 acids decide darkening: chlorogenic versus citric acid
- 2000 and 2001 trials: Russet Burbank darker than Shepody
- 14 elements tested; P, Ca, Cu and Mg linked most to ACD
- 2.5% tuber potassium gives most citric acid, says K+S
Зошто е важно
- За земјоделци
- Пред да изберете сорта за јадење, тестирајте ги примероците со вриење на есен и доцна зима; следете го типот на калиум и почва и прашајте ги одгледувачите за податоци за потемнувањето по складирањето.
- За процесори
- Преработувачи на пржење: сортите се разликуваат по потемнување; натриум киселиот пирофосфат помага само делумно, затоа проверете ја суровината според сортата и периодот на складирање.
- За трговците
- Пакувачи и трговци: потемнувањето расте во складиштето; направете тест за вриење на пролетните парцели пред да ги продадете на малопродажни или угостителски купувачи.
- За добавувачите
- Breeders and seed suppliers: publish after-cooking darkening scores after storage, not only at harvest.
Резиме од 60 секунди
Big yields lose value if the cooked potato goes grey or tastes bitter. Grey or black flesh after boiling comes from iron bound to chlorogenic acid, which oxidises once the potato cools; citric acid ties up iron and limits the effect. Canadian trials in 2000 and 2001 found variety mattered more than location, with Russet Burbank always darker than Shepody, and discolouration grew in both over the storage season. British work from 1967 linked worse results to fen soils poor in citric acid. A study of 14 minerals pointed to phosphorus, calcium, copper and magnesium, and a fertiliser company puts peak citric acid at 2.5% tuber potassium. Table potato growers and packers selling in spring are most exposed, and a boil test on stored samples is a cheap way to spot the problem early. The limitation: most studies are old or cover only a few varieties, and potassium claims come from a supplier.
A high-yielding potato variety does not always pay. If boiled tubers turn grey or black on the plate, or taste bitter, buyers pay less or refuse the lot. Growers often see this in spring, when stored potatoes of such varieties sell at a discount. Two quality traits are behind most of these complaints: after-cooking darkening (ACD) and bitterness.
What causes darkening after cooking
ACD is “one of the most widespread, undesirable characteristics of cultivated potato”, according to a review by Gefu Wang-Pruski and Jerzy Nowak in the Американски весник за истражување на компири (2004). The flesh looks normal after boiling, but turns bluish-grey when it cools in the air. The cause is chemical. Iron in the tuber binds to chlorogenic acid, a natural phenol. After cooking, this iron compound oxidises and forms a dark pigment.
Citric acid protects the tuber, because it binds iron first. The review says the severity of darkening depends on the ratio of chlorogenic acid to citric acid: a higher ratio usually gives darker tubers. Both acids are controlled by genes, but they also change with the growing conditions.
Работни денови. Отпишете се со еден клик.
Older field work in the UK showed the same. J. C. Hughes and J. L. Evans (European Potato Journal, 1967) grew several varieties on a black fen soil and a clay soil. Blackening was usually greater on fen soil, mostly because tubers had less citric acid. Year-to-year changes at one site were mainly due to weather.
Variety, field and store
- Variety. In trials in New Brunswick and Nova Scotia in 2000 and 2001, Russet Burbank always showed more darkening than Shepody. The variety effect was stronger than the location effect, Wang-Pruski and co-authors reported (Acta Horticulturae, 2003).
- Storage. In the same trials, darkening increased during storage in both varieties. This is why a variety can pass in autumn and fail in spring.
- Nutrition. A Nova Scotia study of 14 elements found phosphorus, calcium, copper and magnesium most strongly linked to ACD. Darkening was worst at the stem end. Fertiliser maker K+S says citric acid rises with potassium supply and peaks when tubers contain 2.5% potassium; this is a company claim.
Processors can partly stop ACD in French fries with sodium acid pyrophosphate. Fresh-market buyers cooking at home have no such tool.
Bitterness is a separate problem. It is linked to glycoalkaloids, which rise when tubers are exposed to light; POTATOES NEWS covered this in a separate article on the 200 mg/kg limit.
Зошто е важно
Yield is only one part of a variety’s value. For table potatoes, a variety prone to darkening can lose price after months in store. Before choosing a variety, growers can check official variety lists for cooking quality, ask breeders for ACD data after storage, and test boil samples in autumn and again in late winter. Soil type and potassium supply also deserve attention.
The topic was raised by practitioners in the MAX messenger chat «КАРТОФЕЛЬ И Т.Д. (Potato etc.)», a community of more than 1,100 potato growers and industry specialists. Participants are not named. Придружи се на дискусијата.
Photo: A boiled potato (illustrative). Daderot / Заедничката Ризница, CC0
Глобален компир бриф
Петте најважни вести, цени, известувања за болести и настани. Работни денови наутро, без рекламирање.
Извори
- MAX разговор «КАРТОФЕЛЬ И Т.Д. (Компир итн.)» - https://max.ru/join/SViX6IyOKuJHB6-xuuepbMbts_zk4eiEYdXUpUWVu28
- Wang-Pruski G., Nowak J. Potato after-cooking darkening. American Journal of Potato Research (2004) — https://link.springer.com/article/10.1007/BF02853831
- Hughes J.C., Evans J.L. Studies on after-cooking blackening in potatoes IV. European Potato Journal (1967) — https://link.springer.com/article/10.1007/BF02364255
- Wang-Pruski G. et al. Genetic and environmental interactions affecting potato ACD. Acta Horticulturae (2003) — https://ishs.org/ishs-article/619_5/
- ScienceDaily: Potato after-cooking darkening may be affected by nutrients (2010) — https://www.sciencedaily.com/releases/2010/04/100415171527.htm
- K+S: The ideal potassium fertilizer for potatoes — https://www.kpluss.com/en-us/our-business-products/agriculture/kali-academy/facts-worth-knowing/en-the-ideal-potassium-fertilizer-for-potatoes/
Врска во овој материјал
- Држава
- Светот
- Компании
- К+С
- Технологии
- sodium acid pyrophosphate; boil test
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