Glutinous rice paper made from sweet potato

Starch film, commonly known as glutinous rice paper, is a kind of edible film made of starch as raw material. it is used as a laminated packaging material for candy and pastry in the food industry.

The technological process of making glutinous rice paper: starch emulsification, sieving-mixing paste (phospholipid emulsion)-steam heat preservation-film-making-finished product

1. Starch emulsification and sieving: sweet potato starch is screened by 100 mesh and emulsified by adding water of 50 ~ 55 degrees Celsius. The water consumption is 2.5 ~ 3 times that of starch, and the concentration after preparation is 15,17 Baume degrees, so that the starch is uniformly dispersed in water. Then pass through a 100-mesh copper screen and pump into the gelatinization pot.

2. Paste: after the starch emulsion enters the gelatinization pot, turn on the mixer and add phospholipids to prepare phospholipid emulsion. Phospholipid is an indispensable raw material for the production of glutinous rice paper. in the process of making film, phospholipid can not only help to peel off the film and copper strip, but also prevent the adhesion between the film and the film. Phospholipids need to be dissolved in hot lye by heating 1%-2% caustic soda solution to 85 ℃ 100 degrees Celsius, adding phospholipids under stirring, and heating so that all of them are dissolved in lye. The phospholipid solution with a concentration of 1%-2% was prepared after cooling to 30-40 degrees Celsius, passing through a 100-mesh sieve, the dosage of caustic soda was 0.8%-1.8% of phospholipid, and the pH value of the phospholipid solution was 8-9, showing weak alkalinity.

3. Steam heat preservation: starch gelatinization process. Start stirring when the starch solution is heated to 50 degrees Celsius in a gelatinization pot, add 85-90 degrees Celsius hot water, control the starch concentration at 7%-8%, and keep it at 90 degrees Celsius for 1 hour. The stirring speed should be changed to 40 per minute.

4. Film copying machine: the film copying machine is composed of two aluminum dryers with a diameter of 600 mm, which are connected by a copper strip 13 meters long, 400 mm wide and 0.7 mm thick. The dryer is heated by steam and drives the copper belt forward at the speed of 1 turn per minute. The starch paste flows to the copper strip through a slit 0.14 to 0.15 mm wide, scrapes into a uniform film with a thickness of 2 to 3 silk meters, and is dried and wound on a reel. The film copying machine itself forms a sealing system to control a certain temperature and humidity. The steam pressure in the dryer is controlled at 0.15-0.25 gauge pressure, the pressure should not be too high, otherwise the film will produce many pores, if the pressure is too low, the film will not dry. To spray human steam to adjust humidity in the machine, the operation of the steam is difficult, and the small steam makes the film brittle. The water content of finished glutinous rice paper is not less than 10%. In order to improve the strength of glutinous rice paper, 1% algin can be added before starch gelatinization, and the tensile strength can be increased by about 10%.