Study Of The Taste Improvement Of Old Rice Processed By Ultra-high Pressure Technology

Instant rice are welcomed by more and more consumers because of its convenient to carry, safety and health nutrition, shelf-stable and can be ready to eat in the wild environment. Producing instant rice with stale rice can realize the value of stale rice while reducing production costs. Its prospect market is wide. But the poor grain quality results from poor palatability and easy retrogradation. Instant rice produced by conventional method are difficult to be accepted by consumers. Therefore, to improve the eating quality of instant rice has been concerned by the industry.As a new food processing technology, the ultra-high pressure (UHP) can not only maintain the original flavor and nutrition, but also can make the starch into paste, the protein into gel, making the material surface luminescence and fine texture. Therefore, this paper takes the 1-3 year-old rice purchased from Hefei Changfeng food stores as the research object; it is designed to develop a new instant rice with good aroma and taste by UHP, with improving the eating quality and partially inhibited the rice retrogradation. The main contents and results are as follows.1. The relationship between the sensory index and physicochemical index of the old rice was analyzed, and then the taste evaluation system of instant rice cooked with old rice was constructed.V odor =412.28+2.596 ABS(water absorption)-0.184 HA(hardness);V apparent structure=99.92+0.082 ST(stickiness)-0.044 SE(setback)+0.491 ABS(water absorption);V palatability =22.38-0.03 SE(setback)+301.875 BV(blue value);V taste =154.5+0.09 ST(stickiness)-0.065 SE(setback);V looseness =14.81+0.442 ABS(water absorption)-0.007 SE(setback);Total score=V odor +V apparent structure +V palatability +V taste +V looseness.2. The instant rice taste of 1 year-old and 2 year-old rice can be significantly improved by UHP treatment.The impact of the pressure, pressure sustaining time and pressure sustaining temperature on the eating quality improvement of the 1 and 2 year-old steamed rice was significant, but the impact on the 3 year-old steamed rice was not significant.3. The best UHPP condition for instant rice of 1 year-old and 2 year-old rice was optimized based on the taste score.Results showed that the optimum UHPP parameters for instant rice of 1 year-old rice were pressure of 300 MPa, holding time of 15 min, co-temperature of 50℃. Under the above conditions, the taste score of 1 year-old steamed instant rice increased to 82.54 points from 71.42 points.Results showed that the optimum UHPP parameters for instant rice of 2 year-old rice were pressure of 400 MPa, holding time of 20 min, co-temperature of 50℃. Under the above conditions, the taste score of 2 year-old steamed instant rice increased to 52.53 points from 38.77 points.4. Compound food additives cooperated with UHP can further improve the eating quality of 2 year-old instant rice.Compound food additives (0.80% glycerel monostearte and 0.40% gluconic acid-δ-lactone) cooperated with UHP can further improve the eating quality of 2 year-old steamed instant rice. Under the above conditions, the taste score of 2 year-old steamed rice was 68.61 points, which basically reached the taste score of the un-processed 1 year-old steamed rice(71.41 points). And the score (68.61 points) was equivalent to 74.55% of the taste score of the un-processed steamed new rice.