Impact of starter culture, ingredients, and flour type on sourdough bread volatiles as monitored by selected ion flow tube-mass spectrometry.

This study deals with the detection of volatile compounds originating from the crumb of breads made with sourdoughs obtained through starter culture-initiated fermentations, which differed in flour type (wheat and teff), ingredients (citrate and malate), fermentation time (24h or 72h), and starter culture strains (homo- and heterofermentative lactic acid bacteria species and acetic acid bacteria species) applied. Therefore, selected ion flow tube-mass spectrometry (SIFT-MS) was used. SIFT-MS is an easy-to-use and promising technique in the field of food and flavor analysis. Volatile compounds of crumb samples from the breads with sourdough were measured and compared with those of reference bread crumb samples. In general, sourdough addition had a positive effect on the concentrations of the volatile compounds measured by SIFT-MS. Furthermore, a trend toward higher concentrations of several volatiles was seen upon the addition of sourdoughs that were fermented up to 72h, compared to the addition of sourdoughs that were fermented for a shorter time. Ethanol was the major volatile compound identified tentatively, next to alcohols, aldehydes, esters, terpenes, and heterocyclic compounds. Also acetoin/ethyl acetate could be identified, but these compounds could not be distinguished. Higher alcohols showed an increase upon the use of sourdough fermented for a long time. High concentrations of acetic acid were found in breads made with Gluconobacter oxydans IMDO A845-initiated sourdough, indicating its potential for sourdough production. Breads made with teff sourdoughs were distinct from wheat-based sourdough breads as to their volatile compound profiles.

Van Kerrebroeck S ，Comasio A ，Harth H ，De Vuyst L ... -  《-》

Monitoring of starter culture-initiated liquid wheat and teff sourdough fermentations by selected ion flow tube-mass spectrometry.

Selected ion flow tube-mass spectrometry (SIFT-MS) is a direct-injection mass spectrometric technique that has been introduced recently into the field of food and flavor analysis. It also shows potential for use in the monitoring of food fermentations. Therefore, this study aimed at the online monitoring of different volatile compounds produced during starter culture-initiated liquid sourdough fermentations by SIFT-MS, for which a new workflow was developed. The online monitoring of the volatile sample compounds acetoin and ethyl acetate, diacetyl, and ethanol was made possible during the production of sourdoughs obtained through fermentation with several interesting strains belonging to the species Lactobacillus crustorum, Lactobacillus fermentum, Lactobacillus hilgardii, Lactobacillus nagelii, Lactobacillus sakei, and Gluconobacter oxydans. Acetoin and ethyl acetate could not be distinguished based solely on SIFT-MS data. Diacetyl production was monitored in the case of Lb. crustorum LMG 23699 as a starter culture strain, thereby making the distinction between those volatiles produced in sourdough without extra ingredients added or after the addition of citrate or malate. Starter culture-initiated liquid sourdough fermentations were monitored successfully. The volatile compound production of the different starter culture strains tested reflected differences in their metabolism and/or competitiveness in a sourdough matrix. © 2018 Society of Chemical Industry.

Van Kerrebroeck S ，Harth H ，Comasio A ，De Vuyst L ... -  《-》

Impact of sourdough culture on the volatile compounds in wholemeal sourdough bread.

Sourdough bread has a complex flavour profile, which is strongly influenced by the compounds generated during fermentation by the diverse array of microorganisms present, mainly yeasts and lactic acid bacteria (LAB). Twelve complex sourdough cultures, comprised of mixtures of yeast and bacteria, were propagated using wholemeal flour and used in the production of sourdough breads. The volatile organic compounds (VOCs) present in the sourdough bread crumb were characterised by gas chromatography-mass spectrometry (GC-MS) and proton transfer reaction-mass spectrometry (PTR-MS). Multiple factor analysis (MFA) relating the VOCs and physicochemical features of the sourdough breads (pH, TTA, lactic acid, colour and size) identified three distinct clusters. Cluster 1 was distinguished by VOCs, such as ethanol, 3-methyl-1-butanol, phenylethanol, 2-methyl-1-propanol, acetaldehyde and 2,3-butanedione, along with size related measures and increased production of lactic acid, indicating that yeast activity and homofermentative or facultative heterofermentative LAB were dominant. In contrast, cluster 2 was associated with acetic acid and acetate esters along with acidity related measures indicating a dominance of obligate heterofermentative LAB. Cluster 3 was also related to yeast fermentation activity, but particularly fermentation of lipids with greater production of aldehydes and lactones. The distinct differences between clusters of sourdough breads in their volatile and non-volatile features could be attributed to their fermentation activity and whether the culture was dominated by yeast or the different classes of LAB.

Warburton A ，Silcock P ，Eyres GT 《-》

The addition of citrate stimulates the production of acetoin and diacetyl by a citrate-positive Lactobacillus crustorum strain during wheat sourdough fermentation.

In traditional sourdough fermentation recipes of artisan bakeries, often extra ingredients are added to the flour-water mixture. This may accentuate the aroma and taste of the baked products produced from such sourdoughs. This is made possible, for instance, by stimulating certain microbial activities during fermentation. This study examined the effects of the addition of citrate (a food-grade organic acid present in milk and lemons) on wheat sourdough fermentation in the presence of a citrate-positive, homofermentative, lactic acid bacterial starter culture strain, namely Lactobacillus crustorum LMG 23699. Both liquid and firm wheat sourdoughs were produced. The starter culture strain was able to steer all wheat sourdough fermentations performed, as it always prevailed due to its competitiveness, as shown through culture-dependent microbiological plating and culture-independent bacterial community profiling. Moreover, it possessed all enzyme-encoding genes (as unraveled through genome mining) necessary to convert citrate into desirable compounds such as lactic acid, acetic acid, succinate, acetoin, diacetyl, and 2,3-butanediol. Indeed, citrate addition to the wheat flour-water mixture had an impact on the sourdough fermentation dynamics and thus on the aroma profile of the liquid and firm sourdoughs produced and breads made thereof. A higher final pH, higher total titratable acidity values, and low yeast counts were found in wheat sourdoughs produced with citrate. In particular, the starter culture strain added converted the supplemented citrate into more l-lactic acid as well as acetoin and diacetyl (buttery aroma compounds), which was independent of the dough yield. The buttery aroma compounds were also accentuated in the concomitant breads produced. Further, organic acid production was stimulated in the sourdoughs, whereas increased pyrazine concentrations occurred in the breads. Consequently, citrate supplementation to wheat sourdoughs could be of interest to produce baked goods with enhanced buttery aroma compounds and notes.

Comasio A ，Harth H ，Weckx S ，De Vuyst L ... -  《-》

Effect of a novel Lactobacillus paracasei starter on sourdough bread quality.

The novel Lactobacillus paracasei K5 strain, recently isolated from Greek cheese, was evaluated as potential sourdough bread starter. Breads were made using different amounts of L. paracasei sourdoughs as well as traditional sourdough for comparison. Quality characteristics of the breads (acidity and rising) were examined, as well as rope spoilage through macroscopic observations and molecular analysis (PCR-DGGE). The highest acidity levels (3.15 g lactic acid and 1.13 g acetic acid per kg of bread) and better resistance to rope spoilage were observed when bread contained 30% w/w L. paracasei K5 sourdough. Spoilage in the L. paracasei K5 breads was observed at 15-16 days, 5 days later than the control breads. In addition, L. paracasei K5 sourdough improved the bread sensory properties, as reflected by consumer preference and GC/MS analysis of aroma volatiles. Therefore, L. paracasei K5 can be successfully used for sourdough bread making with good quality and extended shelf-life.

Mantzourani I ，Plessas S ，Odatzidou M ，Alexopoulos A ，Galanis A ，Bezirtzoglou E ，Bekatorou A ... -  《-》