Global: What Makes a Crisping Variety, From 20–25% Dry Matter to Low Sugars
Key takeaways
- 20-25% dry matter is the usual target for crisping stock
- 1.080 specific gravity is about the crisping minimum level
- 8-12 °C storage keeps most chipping stocks from sweetening
- 0.1% reducing sugars is the typical upper crisping target
Why it matters
- For farmers
- Before signing a crisping contract, check the variety record for dry matter, sugars after storage and heat tolerance, not only yield.
- For processors
- Set contract specifications for dry matter and reducing sugars, and favour varieties that crisp light from cooler stores to cut sprout control costs.
- For suppliers
- Breeders can target cold-sweetening resistance combined with stem-end defect tolerance, the two traits that most limit crisp supply.
60-second summary
A good crisping potato is defined less by yield than by chemistry and storage behaviour. Industry guidance cited by PotatoPro asks for about 20 to 25 percent dry matter, roughly a specific gravity of 1.080 or higher, and reducing sugars under 0.1 percent. A 2019 Foods study of 21 clones found dry matter between 18 and 25 percent and noted that chipping stocks are usually held at 8 to 12 degrees to avoid cold sweetening. Denser tubers yield more crisps and absorb less oil, while low sugars limit browning and acrylamide. Warm nights can also cause stem-end defects, to which Snowden and Atlantic are prone and Lamoka and Manistee are more tolerant. Crisp makers, contract growers and breeders are the main audience. The caveat is that the numeric targets come from an industry aggregator and differ by buyer, so each processor contract specification should prevail.
Only a small group of varieties supplies most of the crisp industry. The reason is a narrow set of quality demands. A crisping potato must combine high solids, very low sugars and good storage behaviour.
Dry matter and specific gravity
Crisp makers want dense tubers. According to PotatoPro, the typical target is 20–25% dry matter. That corresponds to a specific gravity above about 1.080. A 2019 study in the journal Foods explained why. Higher dry matter gives more crisps per tonne and lower oil uptake.
In that study, Wayumba and colleagues tested 21 breeding clones. Dry matter ranged from 18.4% to 25.1%. Specific gravity ranged from 1.079 to 1.096.
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Low reducing sugars
Glucose and fructose cause browning in the fryer. The same reaction forms acrylamide. PotatoPro gives a reducing sugar target below 0.1% of fresh weight, ideally below 0.05%. Crisp colour is often scored on a 1 to 5 scale, where 1 is light and 5 is dark.
Storage without sweetening
This is the hardest trait. Most varieties convert starch to sugar when stored cold. The Foods study notes that chipping stocks are stored at about 8–12 °C to avoid this. Cold storage at 4 °C triggers low-temperature sweetening in most varieties.
Warmer stores, however, need sprout control. Since the loss of chlorpropham in the EU, that control is harder and costlier. A variety that crisps well from cooler stores saves energy and reduces the need for sprout suppressants.
Field stress also counts
Some varieties react badly to heat. Stem-end chip defect leaves dark marks at the stem end. Paul Bethke of USDA and the University of Wisconsin told Spud Smart in 2019 that warm nights are a main trigger. Snowden and Atlantic are susceptible, he said. Lamoka and Manistee are more tolerant.
Varieties widely used for crisps include: Atlantic, Lamoka, Lady Rosetta, Snowden.
Why it matters
Crisp makers need year-round supply of light-coloured product. Each extra month of storage raises the risk of sugar build-up. Varieties that tolerate cooler storage and heat stress reduce that risk. For growers, a contract variety is only as good as its storage record. Breeders who combine all these traits in one variety gain a strong market position.
Photo: Potato crisps (illustrative). Gaurav Dhwaj Khadka / Wikimedia Commons, CC BY-SA 4.0
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Sources
- Wayumba B.O. et al., Selection and Evaluation of 21 Potato Breeding Clones for Cold Chip Processing, Foods (2019) — https://pmc.ncbi.nlm.nih.gov/articles/PMC6462922/
- Spud Smart, Stress Factors and Management Practices for Sugar End Disorder and Stem-End Chip Defect (2019) — https://spudsmart.com/stress-factors-and-management-practices-for-sugar-end-disorder-and-stem-end-chip-defect/
- PotatoPro, Potatoes for chips production — https://www.potatopro.com/about/potatoes-chips-production
Linked in this material
- Country
- Global
- Companies
- USDA; University of Wisconsin
- Technologies
- cold-chipping varieties; specific gravity testing
- Sections
- New potato varietyNewsProcessing
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