Due to the improvement of living standards and life-style change today, high-quality, healthy food based consumption has emerged. The general manufacturing process of such fresh-cut vegetables consists of three stages: cutting, washing and packing. Specifically, fresh-cut lettuce may be vulnerable t...
Due to the improvement of living standards and life-style change today, high-quality, healthy food based consumption has emerged. The general manufacturing process of such fresh-cut vegetables consists of three stages: cutting, washing and packing. Specifically, fresh-cut lettuce may be vulnerable to oxidative browning, due to an increase in its tissue damage and respiration rate, while undergoing the processing procedures due to its weak tissues, thus leading to the lowering of its quality and a reduction in its storage time. Browning mechanism of lettuce entailed the generation of phenol materials by PAL activation within the plant body when its tissues were damaged and the generation of melanin caused by the oxidation of phenol materials by PPO activation. Thus, this study conducted a physiochemical treatment that could suppress the activation of PAL and PPO by minimizing the browning index, a quality-lowering aspect for fresh-cut lettuce. As an anti-browning agent, cinnamaldehyde was selected and it postponed the expiration date of fresh-cut lettuce by putting off the point when the initial browning began, by applying the material quality of appropriate knife blades, anti-browning agents with appropriate concentration, temperature of washing water and treatment time. In case of lettuce, the measurement of chromaticity was difficult due to the surface colors of its uneven leaves. This study measured its browning index, by using a colorimeter and a DW extract method that demonstrated a noticeable increase rate in absorbance value, according to the storage time. PAL activation of lettuce was confirmed by an increase in the total amount of total phenolic contents found in lettuce up to 18 hours after it was cut and stored. PPO activation control was measured through the anti-browning test. As a result, 83.27% of PPO activation control was shown in 50 ppm of cinnamaldehyde, signifying the effectiveness of browning control. In order to check the effects of the metal materials of the blades used in the cutting of lettuce on its browning index, the study measured it after cutting it with the blades made of steel, copper, stainless steel, aluminum, brass and ceramic. The results indicated that the ceramic blade resulted in the lowest browning index, thus being designated as the most effective blade material. In case of doing a mid-thermal treatment for lettuce at 40℃ during the washing procedure, there was an effect of browning control. Meanwhile, in order to select the appropriate temperature and time period for fresh-cut lettuce, the study applied various temperatures and immersion time zones. The results demonstrated that 30-second time zone with a temperature of 50℃ had a lower browning index, PPO and PAL activation and higher scores in sensory properties, thus becoming the most effective treatment zone. In the washing procedure, in order to find out the effects of browning control by applying an anti-browning agent into lettuce, the well-known anti-browning agents, such as 1% of ascorbic acid and 1% of citric acid were immersed into 0.1% of cinnamaldehyde and became dehydrated and stored. The results pointed out that the treatment sector with cinnamaldehyde had a lower browning index than other treatment sectors and a lower activation value in PPO and PAL activation measurement, meaning that it was more effective in controlling the browning than ascorbic acid and citric acid. However, the selection of optimal concentration was required in sensory properties, due to the unique odor of cinnamaldehyde. The concentrations used in the experiments as optimal were immersed in 1%, 0.5%, 0.1%, 0.05% of cinnamaldehyde and the changes in each of their browning indices were measured. The results revealed that there were no big differences in the browning indices, PPO and PAL activation between the treatment sectors of every concentration. 0.05% of cinnamaldehyde that had the higher scores in sensory properties on day 8 was selected as the optimal concentration. At 0.05%, the effects were good, but the concentration that was lower than 0.05% was chosen to conduct the combined treatment with mid-thermal treatment. The browning indices were measured at 0.01%, 0.02%, 0.03%, 0.04% and 0.05% of concentrations. The results showed that the treatment sectors at 0.04% and 0.05% had similar values of browning index, PPO and PAL activation and had higher scores in sensory properties than other treatment sectors. Thus, the study chose 0.04% of concentration, which was relatively low, and combined it with the final mid-thermal treatment. Lastly, for the physiochemical combined treatment, the selected ceramic knife blade was used to cut lettuce and it was treated with 0.04% concentrated cinnamaldehyde at the mid-temperature of 50℃ for 30 seconds. Then, it was compared to the control sector treated with 4℃. The results demonstrated that the control sector had its initial browning on day 6 and the combined treatment sector had its initial browning on day 12, thus signifying that the former was effective in extending 6 days of expiration period compared to the control sector.
Due to the improvement of living standards and life-style change today, high-quality, healthy food based consumption has emerged. The general manufacturing process of such fresh-cut vegetables consists of three stages: cutting, washing and packing. Specifically, fresh-cut lettuce may be vulnerable to oxidative browning, due to an increase in its tissue damage and respiration rate, while undergoing the processing procedures due to its weak tissues, thus leading to the lowering of its quality and a reduction in its storage time. Browning mechanism of lettuce entailed the generation of phenol materials by PAL activation within the plant body when its tissues were damaged and the generation of melanin caused by the oxidation of phenol materials by PPO activation. Thus, this study conducted a physiochemical treatment that could suppress the activation of PAL and PPO by minimizing the browning index, a quality-lowering aspect for fresh-cut lettuce. As an anti-browning agent, cinnamaldehyde was selected and it postponed the expiration date of fresh-cut lettuce by putting off the point when the initial browning began, by applying the material quality of appropriate knife blades, anti-browning agents with appropriate concentration, temperature of washing water and treatment time. In case of lettuce, the measurement of chromaticity was difficult due to the surface colors of its uneven leaves. This study measured its browning index, by using a colorimeter and a DW extract method that demonstrated a noticeable increase rate in absorbance value, according to the storage time. PAL activation of lettuce was confirmed by an increase in the total amount of total phenolic contents found in lettuce up to 18 hours after it was cut and stored. PPO activation control was measured through the anti-browning test. As a result, 83.27% of PPO activation control was shown in 50 ppm of cinnamaldehyde, signifying the effectiveness of browning control. In order to check the effects of the metal materials of the blades used in the cutting of lettuce on its browning index, the study measured it after cutting it with the blades made of steel, copper, stainless steel, aluminum, brass and ceramic. The results indicated that the ceramic blade resulted in the lowest browning index, thus being designated as the most effective blade material. In case of doing a mid-thermal treatment for lettuce at 40℃ during the washing procedure, there was an effect of browning control. Meanwhile, in order to select the appropriate temperature and time period for fresh-cut lettuce, the study applied various temperatures and immersion time zones. The results demonstrated that 30-second time zone with a temperature of 50℃ had a lower browning index, PPO and PAL activation and higher scores in sensory properties, thus becoming the most effective treatment zone. In the washing procedure, in order to find out the effects of browning control by applying an anti-browning agent into lettuce, the well-known anti-browning agents, such as 1% of ascorbic acid and 1% of citric acid were immersed into 0.1% of cinnamaldehyde and became dehydrated and stored. The results pointed out that the treatment sector with cinnamaldehyde had a lower browning index than other treatment sectors and a lower activation value in PPO and PAL activation measurement, meaning that it was more effective in controlling the browning than ascorbic acid and citric acid. However, the selection of optimal concentration was required in sensory properties, due to the unique odor of cinnamaldehyde. The concentrations used in the experiments as optimal were immersed in 1%, 0.5%, 0.1%, 0.05% of cinnamaldehyde and the changes in each of their browning indices were measured. The results revealed that there were no big differences in the browning indices, PPO and PAL activation between the treatment sectors of every concentration. 0.05% of cinnamaldehyde that had the higher scores in sensory properties on day 8 was selected as the optimal concentration. At 0.05%, the effects were good, but the concentration that was lower than 0.05% was chosen to conduct the combined treatment with mid-thermal treatment. The browning indices were measured at 0.01%, 0.02%, 0.03%, 0.04% and 0.05% of concentrations. The results showed that the treatment sectors at 0.04% and 0.05% had similar values of browning index, PPO and PAL activation and had higher scores in sensory properties than other treatment sectors. Thus, the study chose 0.04% of concentration, which was relatively low, and combined it with the final mid-thermal treatment. Lastly, for the physiochemical combined treatment, the selected ceramic knife blade was used to cut lettuce and it was treated with 0.04% concentrated cinnamaldehyde at the mid-temperature of 50℃ for 30 seconds. Then, it was compared to the control sector treated with 4℃. The results demonstrated that the control sector had its initial browning on day 6 and the combined treatment sector had its initial browning on day 12, thus signifying that the former was effective in extending 6 days of expiration period compared to the control sector.
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