Yukwa — A Traditional Korean Puffed Rice Snack

Yukwa, a traditional Korean puffed snack made from waxy rice, has long been a popular snack item because of its unique texture and sweet flavor, which results from a coating made with honey or starch syrup (5). Some yukwa products are also coated with puffed or roasted cereal grits for added nutrition and attractiveness. Koreans have traditionally prepared yukwa for festive occasions such as birthdays and weddings, as well as for ancestral memorial services. Today, yukwa has become a popular daily food for many, and there are approximately 200 yukwa factories in Korea (17). Yukwa is made from ground waxy rice with a low amylose content (36). The rice must be steeped in water for a prolonged period of time to produce an optimal texture with small cell structure. Because its qualities depend greatly on processing, it is necessary to identify the optimum conditions for producing yukwa. In recent years, there have been numerous research studies on methods for quality improvement and standardization of the production process for Korean yukwa (3,7,12,15,35). Park et al. (27), Lee et al. (21), and Yu et al. (45) have reported on the physicochemical properties of hydroxypropylated waxy rice starches and their application in yukwa. The influence of steeping and mixing time on quality has been studied by Kang et al. (11), who found that steeping of waxy rice at 15°C for more than 6 days was required to produce a soft texture and small air cell distribution. Mixing of nonwaxy rice with waxy rice has been attempted (36), and different waxy rice cultivars have been compared for their resulting yukwa quality characteristics (2,10). The color, texture, and volatile flavor compounds of traditional Korean yukwa also are affected by the type of packaging material and length of storage (42). Kum et al. (19) and Park et al. (31) found that the addition of antioxidants (tocopherol, oxyfos, or g-oryzanol) to yukwa was effective in extending the shelf life of the product. The effects of microorganism inoculation and enzyme treatment on yukwa characteristics also have been studied (5,29). During production, additives such as rice wine (30), soybean (39), green tea powder (16), and safflower (28) have been mixed with waxy rice flour to create desirable properties in the resulting products.