If you can smell the scent of food in a thoroughly cleaned container, does that imply trace amounts of food particles remain?
It goes without saying that our sense of smell is commonly used in helping identify undesirables in day-to-day life, and as such it's understandable to correlate certain smells to hygiene effectiveness. However, I'd like to definitively understand whether or not the presence of odorants unequivocally indicates ineffective or insufficient sanitation (in particular, on direct food-contact processing utensils and containers in a commercial/industrial environment). E.g., coffee mugs with lingering scent of coffee despite repeated washing.
From the standpoint of HACCP/HARPC, I've always been slightly curious about the absence of "smell" as a modus operandi for pre-operational inspection (visual is the go-to). I've always made the assumption that it simply isn't a reliable sensory indicator (despite visual being the same, in that sense), but I'm not fond of assuming. I have a physics background, but I am unfortunately a bit lacking in biology / chemistry knowledge (beyond food safety-related microbiology).
I'd like to understand from a scientific stand-point: is there an exclusively causal relationship between the two? Are there possible scenarios where we can detect odorants despite having met sanitation performance standards? For the sake of this question, I'd like to preclude the hypothetical possibility that "there were traces of debris/microbiological activity/etc., only they were within the tolerable limit defined".
I'm sure there might be a lot of complexities I am glossing over in my question, for which I apologize; e.g., I am aware in the framing of my question, I am holding some prejudice that the hazards of concern are microbiological -- whether pathogenic or not -- wherein the results from an adenosine triphosphate swab may be used as a quantified measure for overall activity. For the sake of keeping this question from becoming too technical and convoluted to answer, and to also simplify and make measurable the criteria for "sufficient sanitation", please advise from the microbiological stand-point, but if relevant please advise from other standpoints as well (under HACCP/HARPC, the remaining potential hazard categories would be physical and chemical [includes radiological]).