The Effect Of External Airflow Velocity On Product Quality In PM-MAP Packaging

The physiological and biochemical activities of fresh fruits and vegetables during circulation can cause nutrient loss and reduce appearance quality.Perforation-Mediated Modified Atmosphere Packaging(PM-MAP)can slow down the metabolic rate of fruits and vegetables and extend their shelf life by effectively controlling the packaging inner environment.The gas atmosphere inside the package is crucial in maintaining the freshness and quality of fruits and vegetables.However,due to the impact of perforation,the packaging inner environment can experience alterations caused by interference from external airflow,potentially affecting the gas composition inside.This work systematically investigates the effect of external airflow velocity on the quality of fruits and vegetables in PMMAP using simulation modeling and experimental testing.The main research focus and findings are as follows:(1)Using FLUENT software for computational fluid dynamics,the viscous fluid model and SIMPLE algorithm to investigate the impact of various packaging perforation parameters(perforation size and perforation number)and external flow velocity on mass transfer rates inside and outside the packaging as well as airflow processes within the packaging.Simulation results indicate that when the perforation of PM-MAP is located at the top of the packaging,the packaging results in significant airflow obstruction.At an external flow velocity of 1 m/s,the mean wind speed inside the container is approximately 0.074 m/s.At this wind speed,the mass transfer rate inside and outside the packaging is 0.01999 g/s,which is significantly higher than the rate associated with free diffusion through an equivalent-sized perforation.The impact of external gas flow velocity on changes in the internal environment of the packaging is mainly achieved by increasing the mass transfer rate of gas inside and outside the packaging and changing the composition and distribution of gas inside the packaging.Simulations also reveals the influence of various parameters on mass transfer rate:the rate increases with a higher number and larger size of perforations in the packaging,as well as an increase in external flow velocity.(2)Developing a PM-MAP experimental platform for fresh fruits and vegetables,designing air ducts and modified atmosphere boxes,and using 3D printing technology for production.Two typical fruit and vegetable products(brassica chinensis and strawberries)were selected for packaging purposes.The influence of external air velocity on the quality of fruits and vegetables was investigated by measuring weight loss rate,total solids soluble,vitamin C,titratable acid,chlorophyll,leaf chlorosis rate,and sensory quality during storage.(3)Different velocity fields were applied to PM-MAP and quality indicators of brassica chinensis and strawberries were tested.The results showed that PMMAP with an external airflow velocity of 0.5m/s exhibited the best storage quality.At a storage period of 96 hours,the sensory quality of the experimental group was rated at 6.7 points,while the weight loss was 5.678%,the chlorophyll content was 42.4 SPAD,the total soluble solid content was 4.25°Bx,and the ascorbic acid content was 32.93mg/100g.Compared to the control group,storage life was extended by 24 hours.In the modified atmosphere packaging of strawberries,the group with an airflow velocity of 0.5m/s showed better quality.At 60 hours of storage life,the sensory quality scored 5.4 out of 10,the weight loss was 6.54%,the hardness measured 0.99 kg/cm~2,the total soluble solid content was 9.65°Bx,and the ascorbic acid content reached 57.83mg/100g.These results extended storage life by an additional 12 hours compared to the control group.(4)During the experiment,quality indicators such as weight loss rate,chlorophyll content,and leaf chlorosis rate of brassica chinensis deteriorated with the increase of external airflow velocity.The experimental group with lower wind speeds performed better on the two indicators of total solids and sensory quality.Vitamin C content was better maintained as air flow increased.In the experiment,most indicators of strawberries showed the best results at an airflow speed of 0.5 m/s with others;the control group with no airflow and the experimental group with an airflow speed of 2.0 m/s had the worst indicators with others;titratable acid content,which was least affected by airflow speed,was also better than that of the airless control group in all experimental groups.Due to different physiological and biochemical characteristics,brassica chinensis and strawberries have different responses to changes in the external environment of packaging.The impact of external airflow velocity on their quality indicators varies.However,during the experimental process of packaging and storing these types of fruits and vegetables,a lower external airflow velocity(0.5m/s)was beneficial for maintaining most quality indicators.