Journal of Food Hygiene and Safety (한국식품위생안전성학회지)

The Korean Society of Food Hygiene and Safety (한국식품위생안전성학회)
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Changes in Quality of Expired Tofu During Storage at Different Temperatures

유통기한이 경과된 포장두부의 저장온도에 따른 품질변화

  • Kim, Su-jin (Department of Food and Nutrition Yeungnam University) ;
  • Kim, Se-Hun (Food Microbiology Division Food Safety Evaluation Department National Institute of Food and Drug Safety Evaluation) ;
  • Bang, Woo-Suk (Department of Food and Nutrition Yeungnam University)
  • 김수진 (영남대학교 식품영양학과) ;
  • 김세훈 (식품의약품안전평가원 미생물과) ;
  • 방우석 (영남대학교 식품영양학과)
  • Received : 2022.03.23
  • Accepted : 2022.04.06
  • Published : 2022.04.30
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Abstract

The purpose of this study was to examine the microbiological and physicochemical changes on packaged tofu stored at temperatures of 5, 13, 23, and 30℃, and measure the consumable period from the expiry date to ultimately evaluate the microbiological safety on the extension of the consumable period. From the investigation, the pH value of tofu at each storage temperature (5, 13, and 23℃) showed a slight decrease over the storage period, although there was no significant change. The hardness of packaged tofu decreased more rapidly as temperature and storage time increased and the tofu started to show signs of decomposition at the same time. Analysis on the microbial change of tofu at different storage temperature revealed that the number of general bacteria also increased as the temperature increased. It was further found that packaged tofu takes 25 days at 5℃, 7 days at 13℃, and 1 day at 23℃ from the expiry date until the general bacteria count is at least at the early decomposition level which is 10℃ log CFU/g. However, no coliform bacteria was detected from tofu after storing at 5, 13 and 23℃. When packaged tofu was stored at 5℃, the L value changed significantly after 26 days, whereas the a and b values showed no significant change during the storage period (P>0.05). When storing tofu at 13℃ and 23℃ the L value decreased after 8 and 3 days, respectively. However, both a and b values increased (P<0.05).

본 연구는 시판 포장두부를 5, 13, 23, 30℃에 저장하면서 나타나는 미생물학적, 이화학적 변화를 조사하여 두부의 유통기한 경과 후 섭취 가능 기간을 측정하여 소비기한 연장에 대한 미생물학적 안전성에 대해 평가하고자 했다. 저장온도별(5, 13, 23℃) 두부의 pH 측정에 있어서 두부의 저장 기간이 길어질수록 다소 감소하는 경향을 나타냈으나, 큰 차이를 보이지 않았다. 포장두부의 hardness는 온도가 높을수록, 또 저장기간이 증가될수록 급격히 낮아지는 부패 현상을 보였다. 저장온도에 따른 두부의 미생물 변화는 온도가 증가할수록 일반세균수가 증가하였다. 5℃에 저장한 포장두부는 유통기한 경과 후 25일, 13℃에서는 7일, 23℃에서 1일 후 일반세균이 초기부패 수준인 106 log CFU/g이상 검출되었다. 그러나 두부를 5, 13, 23℃에 저장기간동안 대장균군은 음성으로 나타냈다. 포장두부를 5℃에서 저장했을 때 26일후 L 값의 유의적 차이를 나타냈으며, a, b 값은 저장 기간 동안 변화가 있었으나 유의적 차이가 나타나지 않았다(P>0.05). 13℃에서 8일, 23℃에서 3일간 저장하면서 L값은 낮아지고, a, b값은 증가하였다(P<0.05).

Keywords

References

  1. Hwang, T.H., Park, K.H., Harmonization of date marketing for export of Korean foods. Food. Ind. Nutr., 12, 12-18 (2007).
  2. Ministry of Food and Drug Safety (MFDS), Shelf-life guideline (2011).
  3. Korea Food Security Research Foundation (2022, January 27), Forum on occurrence status and reduction method for wasted food. available from: http://www. foodsecurity.or.kr.
  4. Codex., General standard for the labeling of prepackaged foods. CXS 1-1985 (2018).
  5. Ministry of Food and Drug Safety (MFDS), (2011, October 07), Labeling Standards for Food etc. (2021).
  6. Min, Y.H., Kim, J.Y., Park, L.Y., Lee, S.H., Park, G.S., Physicochemical quality characteristics of tofu prepared with turmeric (Curcuma aromatica Salab). Korean J. Food Cookery Sci., 23, 502-510 (2007).
  7. Hwang, T.H., Improvement of shelf-life labeling for effective food distribution management. MS Thesis, Chung Ang University Seoul, Korea (2006).
  8. Korea Consumer Agency (KCA)., The result report on survey for suitability of intake of food that passed the shelf life. (2009).
  9. Korea Consumer Agency (KCA)., The result report on survey for suitability of intake of food that passed the shelf life. (2010).
  10. Korea Consumer Agency (KCA)., The result report on survey for suitability of intake of food that passed the shelf life. (2011).
  11. Ministry of Food and Drug Safety (MFDS)., Shelf life standards for food, food additives and health functional foods (2019).
  12. Ryu, Y.G., Tofu's manufacturing system and market situations. Food Ind. Nutr., 10, 6-10 (2005).
  13. Kim, K.S., Assessment of the shelf lives of packed tofu products. MS thesis, Sunchon National University, Suncheon, Korea (2000).
  14. Shin, H.Y., Ku, K.J., Park, S.K., Song, K.B., Use of freshness indicator for determination of freshness and quality change of tofu during storage. J. Korean Soc. Appl. Biol. Chem., 49, 158-162. (2006).
  15. Lee, Y.B., Kim, T.S., Yeo, I.H., Study on the change of quality index of packed tofu. Korea Soybean Digest., 12, 56-60 (1995).
  16. Wang, C., Zhou, S., Qinling, D., Qin, W., Wu, D., Raheem, D., Yang, W., Zhang, Q., Shelf life prediction and food safety risk assessment of an innovative whole soybean curd based on predictive models. J. Food Sci. Technol., 56, 4233-4241 (2019). https://doi.org/10.1007/s13197-019-03893-5
  17. Lee, K.S., Kim, D.H., Baek, S.H., Choun, S.H., Effects of coagulants and soaking solutions of Tofu (soybean curd) on extending its shelf life. Korean J. Food Sci. Technol., 22, 116-122 (1990).
  18. An, J.H., Park, J.M., Gu, J.G., Yoon, S.J., Lee, J.S., Kim, J.M., Kim, S.H., Kim, R.J., Park, J.W., Song, S.O., Wee, S.H., Kim, J.M., A study of establishment and exploitation of bio-markers for determination of shelf-life of eggs and egg products. Korean J. Food Sci. Ani. Resour., 32, 354-363 (2012). https://doi.org/10.5851/KOSFA.2012.32.3.354
  19. Lee, H.J., Sul, M.S., Cha, B.S., Yook, H.S., Tofu Qualities as influenced by soybeans storage temperatures. J. Korean Soc. Food Sci. Nutr., 27, 833-839 (1998).
  20. Shin, M.K., A study on development of functional tofu by using natural hamcho and deep water-solidifier. PhD Thesis, Kyonggi University, Suwon, Kyeonggi, Korea (2009).
  21. Park, L.Y. Kim SJ. Lee SH., Effect of surface treatment with chitosan on shelf-life of soybean tofu. Korean J. Food Preserv., 12, 516-521 (2005).
  22. Hwang, T.I., Kim, S.K., Park, Y.S., Byoun, K.E., Studies on the storage of functional red soybean curd. J. Korean Soc. Food Sci. Nutr., 30, 1115-1119 (2001).
  23. Ministry of Food and Drug Safety (MFDS)., Korean Food Codex. (2021).
  24. Kim, J.H., Woo, E.Y., Kim, K.H., A study on the soy bean curd(tofu) made from defatted soybean flour. Korean. J. Food Nutr., 19, 22-27 (2006).
  25. Shin, I.S., Development of shelf-life prediction model of tofu using mathematical quantitative assessment model. Food Ind. Nutr., 10, 11-16 (2005).
  26. Kim, J.N., Lee, Y.S., Three dimensional mathematical simulation for predicting the shelf life of tofu packaged in a semirigid plastic container. Korean J. Food Sci. Technol., 41, 272-277 (2009).