How to Storage Potatoes for Frozen French Fries Production Line
As a raw material increasingly being used by the processing industry, the quality of potato is strictly required to produce a high-quality product on a cost-effective basis. Potato storage is designed to control tuber respiration and minimize reducing sugar concentrations in order to favor light colored fries. When potatoes destined for the frozen French fries processing industry are stored, the following measures affecting quality should be taken special care of: ventilation, temperature, sprout inhibitors and conditioning before delivery.
Ventilation (air in/air out) is very important removing tuber moisture, especially early before wounds have healed and skins have fully thickened, relative humidity is held at 90-95% throughout the storage season. After tubers have reached the final storage temperature, ventilation may be needed provide adequate oxygen, meanwhile prevent excess carbon dioxide, and equalize temperatures throughout the storage. Care must be taken to avoid chilling or freezing potatoes near ventilation inlets.
At storage temperatures of 3 – 5ºC, storage losses caused by respiration and fungal or bacterial infection are smallest. But both sugar concentrations and fries color increase with declining storage temperatures. Therefore it is advisable to store potatoes that are intended for the processing industry at relatively high temperatures. Most potatoes for frozen French fries production are stored relatively warm at approximately 7.2-10.0 °C. Some varieties can be stored slightly cooler without sugar buildup and subsequent darkening of fries while others should be stored slightly warmer.
During the first two weeks of storage, potatoes are typically held at about 12.8 °C and high relative humidity (90-95%) to favor suberizing or wound-healing. Then temperatures are slowly dropped ( 0.3 °C per day) until the final holding temperature ( at approximately 7.2-10.0 °C) is reached.
Potatoes form chlorophyll and turn green only when exposed to light. Therefore, greening is controlled by keeping storages dark as much as possible. At a storage temperature of 3 – 4ºC , sprout formation is minimal. However, for decreasing the browning reaction, potatoes for frozen French fry processing should be stored relatively warm at approximately 7.2-10.0 °C . Therefore for potatoes stored more than three months, some method of sprout control is needed. Two chemical sprout inhibitors, CIPC/IPC and Carvone, are in common use for this purpose.
CIPC is quite effective when potatoes are stored at temperatures up to about 12ºC and can be commercially applied any time after the “curing period” but before sprouting begins. The application of Carvone as a biological sprout inhibitor is a new development. It also has a positive effect on the controlling of various storage diseases and it even kills slugs.
Conditioning before Delivery
Potatoes with a high dry matter (high starch) content are more susceptible to black spot. By heating before size grading or delivering, this phemonen will be effectively eased. Allocate at least three days to the heating process with the air temperature not exceeding 20ºC. Potatoes intended for the processing industry should be heated to at least 15ºC. Those with a high susceptibility to black spot should be heated to 18ºC before unloading out of the store.
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