Stress is a rather vague parameter. It should be clarified, and translated into hard and measurable parameters, e.g. high temperature, high humidity, lack of oxygen, lack of food – quantitatively and qualitatively, etc.
All these parameters not only have their influences on the bees, but also determine the fermentation processes inside the hive, such as the making of bee bread. But also take into account the fermentation of sugars by yeasts.
Thus, it is not only a matter of sufficient availability of food, but also of fermentation and the conditions which determine the fermentation processes and the production of odours.
Instead of looking at the micro organisms in the gut of the bees one can try to influence the fermentation in the right direction. See the sheets of my presentation for more about my work in this area:
http://ferrobee.com/wp-content/uploads/Presentationforbeekeeperassociationsversion02-02-2017-compressed.pdf

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