How long can sealed yogurt be unrefrigerated?
By
Dr Tayse Ferreira F. Da Silveira PhD
| Reviewed by
Dr Anny Manrich (PhD)
The contents of this article are fact-based except otherwise stated within the article.
Author bio
Dr Tayse has extensive experience in Food Science, especially through studying the chemical composition and stability of foods, as well as their bioactive properties. She writes and reviews content on these topics.
Dr Tayse da Silveira´s Highlights:
- Lecturer at the State University of São Paulo (Unesp), Brazil, for Food Engineering students
- Post-doctorate in Food Science, with a one-year training period at Cirad – France.
- PhD in Food Science, with a one-year scholarship at the University of Reading/United Kingdom.
- Bachelor of Food Engineering at the Federal University of Pará, Brazil.
“Food Science is exciting because it touches our lives in such personal and intimate ways. Understanding food systems and gaining knowledge of how to manipulate them, helps society evolve as a whole” – Dr Tayse da Silveira.
Professional experience:
In her doctorate at the University of Campinas, Dr Tayse studied the effect of emergent preservation techniques, such as high-pressure processing, on the chemical and microbial properties of foods.
After completing her doctorate, Tayse da Silveira worked as a postdoctoral fellow in the Pharmaceutical Science Department at the University of São Paulo (USP), with a one-year training at CIRAD, Montpellier, France.
During this period, Dr Tayse worked on the development and evaluation of innovative antioxidant molecules for the preservation of fatty food products.
Dr Tayse also taught in public and private universities in Brazil for Nutrition, Food Engineering, and Enology students, always on food science and food technology-related subjects, including microbiology, milk technology, and wine-making technology.
She has also been involved in a number of studies evaluating the chemical composition and bioactive properties of food products, with emphasis on the development of analytical techniques to achieve that.
Currently, Dr Tayse works at the Centro de Investigação de Montanha (MRC), Portugal. She continues to work on the study of the chemical composition of foods, with a focus on identifying and isolating molecules with potential for application as food ingredients.
In her research, she targets molecules able to provide health and nutritional improvement, and antioxidant and antimicrobial properties (natural food additives).
She regularly publishes in high-impact, specialized scientific journals in her field, and feels encouraged to expand her knowledge domain by doing new scientific partnerships.
Education
- 2017 – PhD in Food Science at the University of Campinas Brazil, with a one-year training period at the University of Reading/United Kingdom.
- 2013 – Master’s Degree in Food Science at the University of Campinas, Brazil.
- 2011 – Bachelor of Food Engineering at the Federal University of Pará, Brazil.
Relevant Published work
- Roschel GG, da Silveira TFF, Cajaíba LM, Ferrari RA, Castro IA. Combination of natural strategies to improve the oxidative stability of echium seed oil. Journal of Food Science. 2021;86(2):411-9.
- de Moraes MR, da Silveira TFF, Coutinho JP, Souza DS, Duarte MCT, Duarte RT, et al. Bioactivity of atemoya fruits and by-products. Food Bioscience. 2021;41:101036.
- Ferreira da Silveira TF, Laguerre M, Bourlieu-Lacanal C, Lecomte J, Durand E, Figueroa-Espinoza MC, et al. Impact of surfactant concentration and antioxidant mode of incorporation on the oxidative stability of oil-in-water nanoemulsions. LWT. 2021;141:110892.
- da Silveira TFF, Cajaíba LM, Valentin L, Baréa B, Villeneuve P, Castro IA. Effect of sinapic acid ester derivatives on the oxidative stability of omega-3 fatty acids rich oil-in-water emulsions. Food Chemistry. 2020;309:125586.
- Roschel GG, da Silveira TFF, Cajaiba LM, Castro IA. Combination of Hydrophilic or Lipophilic Natural Compounds to Improve the Oxidative Stability of Flaxseed Oil. European Journal of Lipid Science and Technology. 2019;121(5):1800459.
- da Silveira TFF, Cristianini M, Kuhnle GG, Ribeiro AB, Filho JT, Godoy HT. Anthocyanins, non-anthocyanin phenolics, tocopherols and antioxidant capacity of açaí juice (Euterpe oleracea) as affected by high pressure processing and thermal pasteurization. Innovative Food Science & Emerging Technologies. 2019;55:88-96.
- da Silveira TFF, de Souza TCL, Carvalho AV, Ribeiro AB, Kuhnle GGC, Godoy HT. White açaí juice (Euterpe oleracea): Phenolic composition by LC-ESI-MS/MS, antioxidant capacity and inhibition effect on the formation of colorectal cancer related compounds. Journal of Functional Foods. 2017;36:215-23.
You can view some of Dr Tayse´s work below and links to her professional profile:
ResearchGate: https://www.researchgate.net/profile/Tayse-Ferreira?ev=hdr_xprf
Scopus: https://www.scopus.com/authid/detail.uri?authorId=55901968900
Google Scholar: https://scholar.google.com/citations?user=l4zi0d8AAAAJ&hl=pt-PT
Linkedin: https://www.linkedin.com/in/tayse-ferreira-a2311947/
Reviewer bio
Dr Anny Manrich PhD is a food Engineer with expertise in Food Technology, Natural Polymers, Edible Films, Enzymes, and Nanotechnology. She writes and reviews content on these topics.
Dr Anny Manrich’s Highlights:
- Research and Technology at the Brazilian Agricultural Research Corporation
- PhD in Chemical Engineering with a focus on Biochemistry at the Federal University of Sao Carlos/ Brazil and a one-year scholarship at the Technical University of Munich/ Germany
- Bachelor of Food Engineering at the University of Campinas/ Brazil and a one-year scholarship at the Technical University of Munich/ Germany
“To solve a problem, global vision and multifactorial understanding are necessary. Therefore, in addition to expertise, one should seek multidisciplinary thinking connected with science and reality” – Dr Anny Manrich, PhD.
Professional Experience:
Dr Anny Manrich’s Experience Joining the Brazilian Agricultural Research Corporation, as soon as she completed her doctorate,
Dr Anny Manrich has worked on several projects, including the more than three-year partnership project with BRF, a major food producer in Brazil. As a postdoctoral fellow.
Dr Anny Manrich has also contributed to several business consultancies and research projects of the National Nanotechnology Laboratory System in areas such as food technology, fibres, films and coatings and Nanotechnology; in a very determined way, having a great team relationship, being creative and committed.
Growing concerns about the safe introduction of nanomaterials into today’s life emphasises the need to create regulatory documentation in front of characterising, using and testing them. Dr Anny Manrich worked for two years on a characterization project for nanoscale materials, with the aim of exploring their possible health effects.
Despite not having specific academic training in packaging or polymeric films, Dr Anny Manrich works at the Brazilian Agricultural Research Corporation in areas of edible and biodegradable films produced from agricultural waste and in the development of films with greater resistance to water, having articles published in renowned scientific journals, which demonstrates her multidisciplinary understanding and creativity.
In addition, she worked for four years as a consultant to a food company to develop a line of snacks that are healthy and that add functional ingredients, physiologically active compounds that bring health benefits, made from fruits and vegetables, enabling diet improvement, disease prevention and reduction of nutritional deficiencies.
Dr Anny Manrich participated as a member of the examination board for two Master’s exams and one PhD exam at the Department of Chemical Engineering of the Federal University of São Carlos.
Education:
- 2001 Bachelor in Food Engineering at the State University of Campinas, Brazil
- 1999 One year scholarship at the Technical University of Munich
- 2004 Master in Chemical Engineering at the Federal University of São Carlos, Brazil
- 2012 PhD in Chemical Engineering at the Federal University of São Carlos, Brazil
- 2010 One year scholarship at the Technical University of Munich
The main publications of Dr. Anny Manrich are:
Articles
Manrich, A., Moreira, F. K., Otoni, C. G., Lorevice, M. V., Martins, M. A., & Mattoso, L. H. (2017). Hydrophobic edible films made up of tomato cutin and pectin. Carbohydrate Polymers, 164, 83-91.
Mendes, J. F., Norcino, L. B., Martins, H. H. A., Manrich, A., Otoni, C. G., Carvalho, E. E. N., … & Mattoso, L. H. C. (2020). Correlating emulsion characteristics with the properties of active starch films loaded with lemongrass essential oil. Food Hydrocolloids, 100, 105428.
Norcino, L. B., Mendes, J. F., Natarelli, C. V. L., Manrich, A., Oliveira, J. E., & Mattoso, L. H. C. (2020). Pectin films loaded with copaiba oil nanoemulsions for potential use as bio-based active packaging. Food Hydrocolloids, 106, 105862.
Manrich, Anny, et al. Immobilization of trypsin on chitosan gels: Use of different activation protocols and comparison with other supports. International Journal of Biological Macromolecules 43.1 (2008): 54-61.
Manrich, Anny; Komesu, Andrea ; Adriano, Wellington Sabino; Tardioli, Paulo Waldir ; Giordano, Raquel Lima Camargo . Immobilization and Stabilization of Xylanase by Multipoint Covalent Attachment on Agarose and on Chitosan Supports. Applied Biochemistry and Biotechnology, v. 161, p. 455-467, 2010.
Mendes, J. F., Martins, J. T., Manrich, A., Neto, A. S., Pinheiro, A. C. M., Mattoso, L. H. C., & Martins, M. A. (2019). Development and physical-chemical properties of pectin film reinforced with spent coffee grounds by continuous casting. Carbohydrate polymers, 210, 92-99..
Milessi, T. S., Kopp, W., Rojas, M. J., Manrich, A., Baptista-Neto, A., Tardioli, P. W., … & Giordano, R. L. (2016). Immobilization and stabilization of an endoxylanase from Bacillus subtilis (XynA) for xylooligosaccharides (XOs) production. Catalysis Today, 259, 130-139.
Mendes, J. F., Norcino, L. B., Manrich, A., Pinheiro, A. C. M., Oliveira, J. E., & Mattoso, L. H. C. (2020). Development, physical‐chemical properties, and photodegradation of pectin film reinforced with malt bagasse fibers by continuous casting. Journal of Applied Polymer Science, 137(39), 49178.
Mendes, J. F., Martins, J. T., Manrich, A., Luchesi, B. R., Dantas, A. P. S., Vanderlei, R. M., … & Martins, M. A. (2021). Thermo-physical and mechanical characteristics of composites based on high-density polyethylene (HDPE) e spent coffee grounds (SCG). Journal of Polymers and the Environment, 29, 2888-2900..
Mendes, J. F., Norcino, L. B., Martins, H. H., Manrich, A., Otoni, C. G., Carvalho, E. E. N., … & Mattoso, L. H. C. (2021). Development of quaternary nanocomposites made up of cassava starch, cocoa butter, lemongrass essential oil nanoemulsion, and brewery spent grain fibers. Journal of Food Science, 86(5), 1979-1996.
Manrich, A., Martins, M. A., & Mattoso, L. H. C. (2021). Manufacture and performance of peanut skin cellulose nanocrystals. Scientia Agricola, 79.
Nascimento, V. M., Manrich, A., Tardioli, P. W., de Campos Giordano, R., de Moraes Rocha, G. J., & Giordano, R. D. L. C. (2016). Alkaline pretreatment for practicable production of ethanol and xylooligosaccharides. Bioethanol, 2(1)..
Manrich, Anny, de Oliveira, J. E., Martins, M. A., & Mattoso, L. H. C. Physicochemical and Thermal Characterization of the Spirulina platensis. J. Agric. Sci. Technol. B, v. 10, p. 298-307, 2020.
Book Chapter
Terra, I. A. A., Aoki, P. H., Delezuk, J. A. D. M., Martins, M. A., Manrich, A., Silva, M. J., … & Miranda, P. B. (2022). Técnicas de Caracterização de Polímeros. Nanotecnologia Aplicada a Polímeros, 614.
Conference Papers
Ferreira, L. F., Luvizaro, L. B., Manrich, A., Martins, M. A., Júnior, M. G., & Dias, M. V. (2017). Comparação da estabilidade de suspensões poliméricas de amido/tocoferol e quitosana/tocoferol. In: CONGRESSO BRASILEIRO DE POLÍMEROS, 14., 2017, Águas de Lindóia, SP.
Manrich, A., Hubinger, S. Z., & Paris, E. C. (2017). Citotoxicidade causada por nanomateriais: avaliação do micronúcleo. In: WORKSHOP DA REDE DE NANOTECNOLOGIA APLICADA AO AGRONEGÓCIO, 9., 2017, São Carlos. Anais… São Carlos: Embrapa Instrumentação, 2017. p. 655-658.
Manrich, Anny, et al. Immobilization and Stabilization of Xylanase by multipoint covalent attachment on Glyoxyl Agarose Support. The 31st Symposium on Biotechnology for Fuels and Chemicals. 2009.
Manrich, Anny, et al. Application of immobilized xylanase on hydrolysis of soluble wood hemicelluloses after using microwave and organosolv pre-treatments. The 32nd Symposium on Biotechnology for Fuels and Chemicals. 2010.
You can view some of Dr Anny’s work below and links to her professional profile.
Research Gate: https://www.researchgate.net/profile/Anny-Manrich-2
Scopus: https://www.scopus.com/authid/detail.uri?authorId=23103497100
Google Scholar: https://scholar.google.com/citations?hl=en&user=Ea9qpr0AAAAJ
Linkedin: https://br.linkedin.com/in/anny-manrich-20693129
In this brief guide, we are going to answer the question “How long can sealed yogurt be unrefrigerated?”, and discuss other questions like how to store the yogurt, and how to know if your yogurt is good to eat or not.
How long can sealed yogurt be unrefrigerated?
You can keep your yogurt unrefrigerated for 2 hours [1], after that, it can start to undergo undesirable alterations and be no longer safe to consume.
If the room temperature is 30°C or higher, unwanted alterations can occur even faster, and that two-hour window is shortened to one hour. This applies to all forms of yogurt.
Yogurt generally is acidic and is not spoiled by most bacteria. The acid also restricts the growth of most food-poisoning bacteria. The high acidity makes yeast the major spoilage organisms of yogurt, together with molds [2].
Upon temperatures between 4-60°C, microbes’ growth takes place at a faster pace [1]. Therefore, yogurt should be refrigerated at 4°C to achieve a shelf life of 7 to 14 days, otherwise, it will spoil and become unsafe.
What are the risks of leaving yogurt unrefrigerated for too long?
Some people might say they keep their yogurt unrefrigerated for 6-8 hours mostly when they bring it to work and it tastes good. Indeed, yogurt going bad depends on temperature and other factors like acidity, and sugar content.
Additionally, the high acidity of yogurt inhibits the growth of most harmful bacteria. But, we would recommend you refrigerate yogurt within two hours. It may not taste bad, but still, there might be spoilage that you can not see.
According to Bozoglu [2], two harmful bacteria, namely Escherichia coli O157:H7 and some strains of Listeria monocytogenes are able to survive or adapt to acidity and remain in yogurt during the storage period.
These microorganisms can cause diarrhea, stomach cramps, vomiting and even death.
Recent outbreaks involving Greek yogurt contaminated with E.coli O157:H7 have been reported [3]. Sixteen people were affected, among them, some children.
Related symptoms included severe stomach cramps, bloody diarrhea, fever, and, in severe cases, kidney failure complication [3].
In another recent product recall, a blueberry yogurt was detected contaminated with molds. Although no confirmed illnesses had been reported, molds can produce toxins that pose a risk to human health [2,3].
We can say that cases like those are not usual in the dairy industry, but you never know when they could happen. Thus, it is better not to take the risk and protect yourself from unpleasant surprises with your yogurt.
Besides safety issues, the quality of the yogurt can be damaged, as the yogurt bacteria continue to produce acids, which are boosted by high temperatures, causing an objectionable sharp acid taste [2].
Bozoglu [2] also stated that some spoilage yeast species, such as Rhodotorula glutinis, Yarrowia lipolytica, may cause quality problems in yogurt stored at relatively higher temperatures (such as 15–20 °C).
How to know if your yogurt is good to eat or not?
Yes, you can decide if your yogurt is good to eat or not just by looking for some signs. Let’s find out what are those changes that indicate the yogurt has gone bad.
1. Too acidic taste
If you feel your yogurt is more acidic than normal, this can be the result of bacteria in yogurt continuing to produce acid. Bacillus is the predominant type of spoilage bacterium in yogurt, followed by Lactobacillus, Streptococcus, and Actinomyces [2].
When leaving your yogurt unrefrigerated, these microorganisms multiply faster. But they are not harmful to your health. In this case, your yogurt is still safe to consume, it just does not taste as good as before.
2. Detection of off-flavors and off-odors
Yeasty, fermented, or fruity off-flavors are the result of yeast growth, the main spoilage microorganism in yogurts [2]. If you are able to detect these signs this indicates a high contamination by yeasts.
The most common yeast spoilage is caused by S. cerevisiae (the same one used to produce beer, bread, and wine). Higher temperatures stimulate the growth of yeasts.
It is advisable to discard the yogurt if you find it like this.
3. Presence of gas
A gassy appearance shows up due to the production of gas (carbon dioxide) by yeasts [2]. It is advisable to discard the yogurt if you find it like this.
4. Presence of molds
The molds can grow on the surface of yogurts stored for a longer time. When you open a container and you see green, off-white, black growth on the yogurt surface it is mold. It will kill all the good bacteria and will have a foul smell.
You should immediately discard the yogurt container.
5. Color change
According to Bozoglu [2], the growth of yeasts and molds in yogurt causes heterogeneous color distribution on the surface of yogurt, particularly when stored at higher temperatures than recommended.
If you notice any color change in your yogurt, discard it.
How to store your yogurt?
· Store your yogurt in the refrigerator at 4°C. Unopened it will last for 7 to 14 days. After opening, it lasts for about 2 days.
While in the refrigerator, keep the yogurt well sealed. This will avoid contamination and the yogurt pick up odors from the surrounding.
· If you do not wish to finish the whole yogurt container at once then make sure to use a different spoon and not one you are eating with. Take out the portion on a plate, seal the container, and keep it back in the fridge.
For liquid yogurts, take a serving in a glass and do not drink directly from the bottle top, it will bring contamination to the remaining content in the bottle.
· While making yogurt at home, always use pasteurized milk. Make sure to sanitize all the utensils you use, to avoid the addition of unwanted bacteria.
· If you leave your yogurt out by mistake make sure to refrigerate it within 2 hours.
Frozen yogurt can have a shelf life of 1 to 2 months. But may lose texture and color after thawing.
Conclusion
In this brief guide, we answered the question “How long can sealed yogurt be unrefrigerated?”, and discussed other questions like how to store the yogurt, and how to know if your yogurt is good to eat or not.
Citations
2. (2016). Spoilage of Milk and Milk Products. In Food Microbiology: Principles into Practice (eds O. Erkmen and T.F. Bozoglu)
