Konjac (also known as arum, konjac, konjac, etc.) is an Araceae herbaceous plant with oblate spherical tubers underground. It is an emerging cash crop and has become an important agricultural product. It is mainly cultivated in southwest my country and the middle and lower reaches of the Yangtze River, and its resources are very rich. Konjac gum (also known as konjac powder) can be extracted from the tubers of konjac. Its main component, konjac glucomannan (KGM), is a non-ionic water-soluble polymer natural plant polysaccharide. Depending on its type and growth period, the content of konjac gum in konjac tubers is also different. It can reach 10% to 30% in fresh mature konjac, and it can reach 50% to 80% in crude konjac powder.
KGM has various characteristics such as gelling and edible properties, so it is widely used in food, biology, medicine and other fields. However, it has problems such as large molecular weight, high viscosity, low solubility, difficulty in digestion after consumption, and easy to cause abdominal distension. Therefore, Application in the food field has been subject to certain restrictions. However, by modifying its viscosity, konjac oligosaccharides with small molecular weights can be obtained, which can be used as ideal food raw materials or food additives. On November 26, 2013, the National Health and Family Planning Commission issued Announcement No. 4 of 2013, officially approving konjac oligosaccharide derived from konjac as a new food raw material. This will promote the use of konjac oligosaccharide as a new food raw material in food. Especially widely used in functional foods. Therefore, changing the viscosity of konjac gum is an effective way to broaden the application range of konjac gum. The structural properties, viscosity modification and application of konjac gum in food are reviewed below.
KGM is mostly white powder, has no peculiar smell, has strong swelling ability, and can absorb 80 to 100 times of its own weight in water. It is soluble in dilute acid and dilute alkali at room temperature, but insoluble in organic solvents such as ethanol and chloroform. Konjac gum is the most viscous edible gum among hydrophilic colloids. The viscosity of 1% konjac gum solution is 1000-40000 mPa·s. High-concentration (>1%) konjac gum solution is a typical pseudoplastic fluid. Konjac gum has various properties such as water retention, gelling, thickening, suspending and emulsifying properties. Compared with additives such as xanthan gum, guar gum, and locust bean gum, konjac gum is less affected by salt, and konjac gum is uncharged and is miscible with most cationic, anionic, and nonionic edible gums. Synergy or synergy. In addition, konjac gum also has some health care functions. It has certain curative effects on human digestive tract diseases, cardiovascular diseases, diabetes and some tumors, and can be used for weight loss.
2. Application of modified konjac gum in food
Konjac gum improves the quality of food through physical modification, chemical modification, and biological modification. KGM is processed through different modification methods to obtain konjac oligosaccharides with smaller molecular weights to reduce the viscosity of the colloid, thereby making it easier to stir during food production. Konjac oligosaccharide can be added to solid beverages, yogurt and ice cream as a thickener and stabilizer solution with low viscosity. Wu Yuejiao et al. have formulated konjac oligosaccharides to produce a konjac suspension drink with better stability. In addition, konjac oligosaccharides can be used to make konjac noodles, konjac vermicelli, konjac tofu and other foods with excellent elasticity and toughness; konjac oligosaccharides can also be used as excipients to make konjac jelly and konjac gummies with better transparency and chewiness. food.
3. Application of modified konjac gum in food preservation
Modified konjac gum can be used to make food preservation coatings. The film preservation method is a fruit and vegetable preservation technology widely used at home and abroad. This method is low-cost, easy to operate, has the effect of preservation and antisepsis, and can extend the shelf life of food. The edible film is covered on the surface of fruits and vegetables by brushing and spraying. It can not only reduce the loss of water in fruits and vegetables during storage, but also can regulate the spontaneous atmosphere of fruits and vegetables, weaken the respiration intensity of food, and inhibit the consumption of nutrients. At the same time, it can also isolate external pollution, inhibit the invasion and reproduction of germs, and play a certain mechanical protection role.
4. Application of modified konjac gum in low-fat foods
Sausage is a pork product prized for its unique cured meat flavor. In recent years, with the changes in people's consumption concepts, the consumption of sausage has gradually declined, mainly because of its high fat content, which is not good for human health and is not recommended for some special groups such as hyperlipidemia. The development of new food raw materials konjac oligosaccharides will contribute to the further development of the food industry. Research shows that konjac oligosaccharide can be used as a fat substitute to partially replace lard and be added to sausages to produce low-fat sausages without affecting its taste and flavor, thereby achieving the purpose of controlling the fat content in food. In addition, konjac can also be used as a food raw material to process and produce konjac bionic products with different flavors, such as bionic beef, vegetarian shrimp, etc., to meet a variety of consumer needs.
The konjac oligosaccharide obtained by modifying the viscosity of konjac gum is water-soluble and indigestible, and also has certain sugar properties such as sweetness and viscosity. It can be widely used as an excellent food ingredient in various foods. Our country is very rich in konjac resources, but the deep processing of konjac is far from enough. Modern high and new technologies are used to further conduct in-depth research on the functional properties, application forms and mechanisms of modified konjac gum, especially the research on enhanced functions and mechanisms. , prompting its wider application in food, health care products and other industries. Our country exports more than 10,000 tons of konjac products to Japan, Europe, the United States, South Korea and Taiwan through various channels every year. Especially in recent years, the market demand for healthy foods has been increasing day by day. Foods and food additives based on konjac have gradually replaced traditional carrageenan, agar, and expensive seaweed extracts. Conduct extensive research on the comprehensive utilization of konjac resources, utilize alkaloids, proteins, starch and other by-products in konjac, and continuously increase the added value of konjac. The konjac industry will have broader development prospects.