Keep Hot Food Hot, Cold Food Cold, Prof. Olanbiwoninu Warns

Nigerians have been warned to keep hot food hot and cold food cold to avoid time and temperature abuse and ensure food safety.

The warning was given by the 32nd Inaugural Lecturer of Ajayi Crowther University (ACU), Oyo, Prof. Afolake Atinuke Olanbiwoninu, while delivering a lecture titled Invisible Giants: The Microbial Forces Securing Food, Protecting Health and Sustaining Life on Earth, on Tuesday, October 6, 2026.

Prof. Olanbiwoninu, an expert in Food Microbiology, emphasised the 2-Hour/4-Hour Rule, explaining that time and temperature abuse occurs when food remains in the Temperature Danger Zone between 5°C and 60°C for too long.

"Food left in this zone for under 2 hours can be used or chilled; between 2 and 4 hours, it must be used right away, and after 4 hours, it must be thrown out. No seasoning, regardless of its antimicrobial properties, can replace sound food-handling practices," she said.

Her take-home message was: keep hot food hot, keep cold food cold, and do not rely on seasoning to make poorly stored food safe.

Illustrating her research with a study on the Survival Pattern and Toxin Production of Pathogens in Spiced and Non-Spiced Fried Rice, the don noted that ready-to-eat foods commonly served at Nigerian social gatherings such as weddings, conferences and religious celebrations are often prepared in large quantities well in advance and held at ambient temperature until serving.

She disclosed that findings from the study were both enlightening and troubling, as pathogenic organisms such as Escherichia coli, Salmonella typhi, Bacillus cereus and Staphylococcus aureus multiplied rapidly as holding temperatures declined and storage time increased.

She submitted that many outbreaks of food poisoning associated with social events do not result from inadequately cooked food, but rather from improper handling after cooking.

While acknowledging that traditional spices such as garlic, ginger, thyme and curry inhibited microbial growth to varying degrees, she warned that the antimicrobial properties of spices should not be misunderstood.

"Although they reduced microbial proliferation, they did not eliminate foodborne pathogens or prevent toxin formation during prolonged storage," she said.

Turning to fresh fruits and vegetables, she noted that unlike cooked foods, fruits do not undergo heat treatment that can destroy pathogenic microorganisms before consumption, yet many are consumed raw.

She cited her research on microorganisms associated with spoiled tomatoes sold in local markets, popularly called esha in Yoruba, revealing that financial constraints often lead consumers to buy partially spoiled tomatoes because they are cheaper.

According to her, investigations revealed numerous bacterial and fungal species associated with spoiled tomatoes, several of which exhibited high levels of antimicrobial resistance.

She stressed that consumer behaviour is influenced not only by scientific knowledge but also by economic circumstances, adding that effective food safety interventions must recognise the complex interactions between poverty, food security, market dynamics and public health.

In conclusion, she described microorganisms as invisible giants, saying: "Although invisible to the naked eye, microorganisms sustain ecosystems, recycle nutrients, enrich soils, preserve foods, improve nutrition, protect public health, and provide innovative solutions to challenges that confront every nation."

She called for microbiology and biotechnology to be central to national development strategies as Nigeria seeks to strengthen food security, improve public health, diversify its economy and build a resilient bioeconomy.

In her recommendations, she urged government, academia, industry and development partners to promote indigenous fermented foods, strengthen national food safety systems, increase investment in microbiology and biotechnology, address micronutrient deficiencies, strengthen antimicrobial resistance surveillance through a One Health approach, and recognise microbiology as a strategic national intellectual asset.

Earlier, the Vice-Chancellor, Prof. Ebunoluwa Oduwole, described the inaugural lecturer as a multiple research grant and award winner who has contributed significantly to the development of Ajayi Crowther University. The lecture was also graced by the immediate past Vice-Chancellor, Prof. Timothy Adebayo, among other dignitaries.

Photo Credit: Victorious Cinematography