435 student brothers showcase 307 innovative achievements
How can vegetables be processed to reduce the loss of vitamin C? How do the disposable chopsticks on the market exceed the bacteria standard, and can it be effectively reduced by rinsing with tea or warm water? The 29th Guangdong Youth Science and Technology Innovation Competition was held in Guangzhou No. 6 Middle School from March 29th to 30th. 435 students from cities across the province presented 307 innovative achievements at the venue. The reporter found that many of them are closely related to daily life.
Why is the boiling water not sterilized thoroughly?
◆ 1. Although the boiling water temperature is high, the processing time is too short to be well sterilized
◆ 2. The temperature of tea and warm water is too low, it is difficult to kill microorganisms on chopsticks
Three students, Liu Jiale, Gong Wenyuan, and Liu Xiangyi from Wenyuan Middle School in Zhuhai, studied the use of disposable chopsticks and the microbial content of wooden and bamboo disposable chopsticks. "We hope to reveal the true face of disposable chopsticks and keep more people away from disposable chopsticks." Gong Wenyuan said.
For the use of disposable chopsticks, the research team issued a total of 165 questionnaires and recovered 160. When investigating the reasons for choosing disposable chopsticks, it was found that 15.63% of people chose "for convenience", 78.13% chose "last resort", and only 6.25% chose disposable chopsticks because of "sanitation". It can be seen that most people are "forced" to use disposable chopsticks, which coincides with the fact that many restaurants only provide disposable chopsticks. After being informed of the dangers of disposable chopsticks, 91.88% of the surveyed people said they would "not use them as much as possible", but 8.13% would continue to use them because of their convenience.
"The survey results show that it is feasible to uncover the hygiene status of disposable chopsticks and guide the public away from disposable chopsticks accordingly." The research team believes.
The study carried out microbiological detection on disposable chopsticks made of different materials. The study found that, whether it is wooden or bamboo disposable chopsticks, the bacteria and mold content are seriously exceeded (the national health standard stipulates that the total number of bacteria per milligram sample is less than 200 and the mold per milligram sample is less than 50). Calculated by a pair of chopsticks at about 10 grams, the disposable bacteria content of wooden disposable chopsticks exceeds the standard by nearly 24 times and the mold content exceeds 32 times. The disposable bacteria content of bamboo disposable chopsticks exceeds the standard by nearly 52 times and the mold content exceeds the standard by 32 times. The research team also found that larvae were grown in the culture medium, so it can be inferred that disposable chopsticks also contain worm eggs. If the human body intakes them, the incidence of parasitic diseases is greatly increased.
The experiment also found that the bacteria content of chopsticks decreased after boiling water treatment but still maintained a high level. After conversion, the number of bacteria per pair of chopsticks after boiling water treatment is 3.6 × 107, which is 18 times the national health standard content. The bacterial content of chopsticks treated with tea and warm water is 21 times and 26 times the hygienic standard, respectively.
"It can be seen that the disposable chopsticks rinsed before meals in daily life have a certain effect on reducing the bacterial content, but the effect is not ideal. Main reasons: 1. Although the boiling water temperature is high, the processing time is too short to play a Good sterilization effect; 2. The temperature of tea and warm water is too low, it is difficult to kill the microorganisms on the chopsticks. "The experimental team members explained.
How to reduce vitamin C loss in vegetables?
Experimental results Wash → Hand tear → Instant cooking (fried)
Jiang Zezhou, Ye Zilin, and Zhu Huatao from the Children's Palace of Yuexiu District of Guangzhou, three fourth-grade students, studied the effects of different processing methods on the loss of vitamin C in vegetables. They concluded that tearing by hand and cooking immediately after washing can improve the preservation of vitamin C. Their group is called "Zhu Jiang Ye You".
The "Zhu Jiang Ye You" group first selected spinach and Chinese cabbage as research objects. They bought these two vegetables from a nearby vegetable market, and then did 9 steps of processing: including selecting vegetables, washing vegetables, weighing samples, cooking vegetables, grinding samples, preparing centrifugation, centrifuging (extracting Vitamin C), Take the supernatant and titrate (measure the vitamin C content in 1 ml of the supernatant).
After experiments, it was found that the results of spinach and cabbage were roughly the same. Compared with spinach and Chinese cabbage when not cooked, the vitamin C content of all spinach and Chinese cabbage after treatment decreased. This shows that various pre-cooking processes and re-cooking processes will cause loss of vitamin C. "It can be seen from the experiments that in order to preserve as much vitamin C as possible after cooking spinach and cabbage, the best way to prepare spinach and cabbage before cooking is: wash → tear by hand → cook immediately (fried)." They introduced.
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