Gas sensor, refrigerator having the gas sensor and method of controlling the refrigerator

1. A refrigerator comprising:

a storage chamber;

a cooling unit configured to supply cold air into the storage chamber;

a gas sensor configured to determine a state of a food in the storage chamber, the gas sensor comprising:

a hydrogel support including a dye configured to change color based on a pH change due to a reaction with a target gas;

an optical sensor configured to detect the color of the dye; and

a control unit configured to determine a state of a target food based on the color detected by the optical sensor and to control a temperature of the refrigerator by providing a control signal to the cooling unit according to the determined state of the target food,

wherein the hydrogel support includes a hydrogel including at least one of agar, agarose, sodium alginate, potassium alginate, rubidium alginate, calcium alginate, barium alginate, and propylene glycol alginate.

2. The refrigerator according to claim 1 , wherein the dye of the gas sensor comprises at least one of a natural dye and a synthetic dye.

3. The refrigerator according to claim 2 , wherein the natural dye comprises an anthocyanin-based dye.

4. The refrigerator according to claim 2 , wherein the natural dye comprises a dye extracted from at least one of red cabbage, blueberry, apple, pear, peach, asparagus, strawberry, pomegranate, and grape.

5. The refrigerator according to claim 2 , wherein the synthetic dye comprises at least one of chlorophenol red, methyl red, bromothymol blue, bromocresol green, nitrophenol, bromocresol purple, and alizarin.

6. The refrigerator according to claim 1 , wherein the target gas of the gas sensor comprises at least one of a volatile organic acid and a base.

7. The refrigerator according to claim 6 , wherein the volatile organic acid comprises at least one of carbon dioxide and acetic acid, and

the base comprises ammonia.

8. The refrigerator according to claim 1 , wherein the hydrogel support of the gas sensor is provided to solidify a hydrogel.

9. The refrigerator according to claim 1 , wherein the hydrogel support of the gas sensor has a cross-linked structure formed by a cross linking agent comprising a divalent cation.

10. The refrigerator according to claim 9 , wherein the divalent cation comprises calcium ion, and

the cross linking agent comprises calcium chloride.

11. The refrigerator according to claim 1 , wherein the hydrogel of the hydrogel support of the gas sensor comprises natural hydrogel.

12. The refrigerator according to claim 1 , wherein the hydrogel support of the gas sensor comprises at least one of glycerin, glycerol, propylene glycol, sorbitol, maltitol, polydextrose, triacetylglycerol, potassium lactate, isomalt, xylitol, sodium lactate, urea, glycosaminoglycan, poly vinyl alcohol, calcium chloride, and sodium chloride.

13. The refrigerator according to claim 1 , wherein the gas sensor is manufactured in a sheet.

14. The refrigerator according to claim 13 , further comprising a membrane coupled to one surface of the hydrogel support provided to contact the target gas.

15. The refrigerator according to claim 1 , wherein the gas sensor is used to measure at least one of a freshness, a degree of maturity, and a degree of fermentation of foods.

16. The refrigerator according to claim 1 , further comprising:

a storage container comprising a transparent section,

wherein the gas sensor is disposed inside the transparent section of the storage container.

17. The refrigerator according to claim 1 , further comprising:

a display unit configured to display the determined state of the food.

18. The refrigerator according to claim 1 , wherein the control unit stores information about a relation between a signal output from the optical sensor and the state of the food, and determines the state of the food according to the stored information.