Can instrumental characterization help predicting sour taste perception of wheat sourdough bread?

The highlights posted above tell you most of what you (I) want to know. Here is a bit more that I found interesting.

Acidity actually constitutes the only requirement for a bread to be sold under the denomination “Pain au levain” (sourdough bread) in France, i.e. bread must have a pH below 4.3 and an endogenic acetic acid content superior to 0.9 g/kg.

For this study, four different sourdoughs were used for breadmaking. They were traditional sourdoughs, selected for their diversity in terms of microbial composition, acidity and FQ (data not shown), coming from four different bakeries of the area

I was surprised at the amounts of "sourdough" (I assume starter) they used. 

The recipe for bread dough varied according to sourdough DY as shown in Table 1. Doughs were prepared by mixing firstly flour and water for 4 min at 80 rpm and 1 min at 120 rpm with a Diosna spiral mixer (Dierks & Söhne GmbH, Germany). After 30 min of resting, sourdough, salt and potentially yeast (B4) were added to the dough and mixed for 8 min at 80 rpm and 4 min at 120 rpm. After a rest of 60 min at 20 °C and Relative Humidity (RH) of 80%, the dough was divided into 500 g loaves and moulded manually. The duration of second proofing at 20 °C, RH 80%, varied from one formulation to the other as shown in Table 1. The loaves for B5 bread were degassed manually before baking by flattening them with the palm of the hand to artificially increase its density. All loaves were partially baked at 220 °C for 20 min, left to cool for 3 h, packaged in protective atmosphere and stored at 4 °C. Prior to analysis, loaves of pre-baked bread were fullybaked at 230 °C for 20 min and left 2 h to cool.

Bread acidity was determined by measurements of pH, Total Titratable Acidity (TTA) and organic acid quantitation. Ten grams of bread crumb were homogenised with 90 mL of distilled water in a Stomacher for 2 min. Then, 25 mL of the mixture was used for pH and TTA determination with an automatic titrator

The sour taste of breads obtained as described previously was evaluated by two types of sensory analysis: Progressive Profiling (PP) and Quantitative Descriptive Analysis (QDA). A panel of 15 healthy volunteers (10 women and 5 men, aged between 23 and 62) was recruited based on their motivation and discrimination abilities

 Surprisingly, acetic acid content of breads related to the Fermentation Quotient showed no effect on sour taste perception neither statically (QDA), nor dynamically (PP).

Finally, from all the physicochemical characteristics monitored, bread pH was the best correlated to sour taste, explaining up to 97% of sour taste variations evaluated by QDA. Measuring bread pH could therefore constitute a quick and easy way to predict bread sour taste perception.

Seems like a carefully done study. The "Progressive Profiling" was new to me; I'm amazed you could get people to report that finely on their perceptions.

Seems like the French rule makers knew what they were doing.