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The production of composite or double-layer (DL) bread was optimized to reduce the amount of the chemical preservative calcium propionate. It was validated using sourdough (SD) in the crust (0–80 g/100 g crust dough). Par-baked (PB) and fully baked (FB) breads were evaluated based on their shelf-life extending, bread technological and sensorial properties. The shelf-life of PB bread was increased with ≥60 g SD/100 g crust dough for air packaged and ≥20 g SD for modified atmosphere packaged (MAP) breads. Use of 60 g SD/100 g crust dough was sufficient to achieve the same level of preservation with or without MAP. Par-baked and fully baked bread were mould free for respectively 7 and 30 days using 60 g sourdough in 100 g crust dough. Specific volume decreased for PB bread containing 40–60 g SD/100 g crust dough and for FB bread with 80 g SD/100 g crust dough. Accordingly, crumb hardness was impaired under the latter conditions.

The impact of processing conditions on the microbial quality of par-baked wheat and sourdough bread was investigated. Processing conditions included par-baking time (8 and 13 min), temperature (150 and 200 °C), amount of steam (200 and 600 mL), and packaging (air and modified atmosphere (MA)). Total anaerobic mesophilic plate counts, moulds and yeasts and spore-forming bacteria, together with pH and aw of the par-baked breads were evaluated. Data were used to make predictive models showing the impact of the main effects and their interactions. Sourdough addition could extend the time of acceptable bread quality based on the anaerobic counts from 8 to more than 13 days. Visual growth of moulds and yeasts (presence/absence of single spots) was most efficiently suppressed by the combination of MA-packaging and the highest baking temperature and time. Microbiological analysis of moulds and yeasts however, showed that again sourdough had the best preservation potential, followed by MA-packaging. This study showed that adjusting the par-baking conditions, bread composition and packaging can increase the shelf-life of par-baked bread in a natural way.

Plant oils have potential as antimicrobial ingredients in bread. However, they may influence bread production. This study compares the influence of blackcurrant (BC), cumin seed (CS), thyme (TH) and wheat germ (WG) oil on the technological quality of dough/bread, as well as their antifungal activity. The influence of the oils was tested on the water absorption and kneading properties of dough, elasticity, starch gelatinization and yeast activity and were compared with a control without oil and a reference with calcium propionate. Bread weight, volume, color and crumb texture were evaluated. The antifungal activity was tested through a shelf-life test of breads. Results showed that, generally, the addition of oils resulted in a decrease of dough consistency. WG showed the highest overall resemblance with the control concerning water absorption and kneading properties of the dough. Additionally, WG and TH were the only oils that could extend the shelf-life. WG caused a shelf-life increase of 3 days (+33%), TH 20 days (+100%). However, TH had a negative impact on dough rheology and yeast activity due to the high presence of thymol. In conclusion, it can be stated that WG showed the most promising combined technological and microbiological benefits in dough/bread.

This review addresses the recent advances of the application of essential oils (EOs) in in vitro systems and in bread systems for the reduction of fungal spoilage. Given the number of research articles concerning the use of EOs as potential antifungal food preservatives, it is generally accepted that they must be given further attention for use in specific food matrices. However, despite the numerous articles stating the antifungal effect of EOs, very few report the actual application in bread or other bakery products and the impact addition can have on dough and bread production, physico-chemical, microbiological and sensorial quality. Advances have been made in the area of food preservation, but further research is necessary to fully comprehend the mode of action and to establish actual food applications of EOs in the bread and bakery industry.

In this study, the incorporation of leek in wheat bread was explored. Green leek leaves were dried with two techniques to obtain leek powder after milling. The air-dried and freeze-dried powders were incorporated into wheat flour at five substitution levels (0, 0.5, 1, 1.5 and 2 g/100 g). The impact of leek powder on dough rheology, bread quality, sensory evaluation and mould-free shelf-life was investigated. Leek powder negatively impacted the mixing properties and significantly changed the viscoelastic properties of the wheat flour dough. At low levels, the dough was strengthened whereas at higher levels both dough resistance as extensibility decreased. Bread quality was also affected, resulting in lower bread volume and coarser crumb structure. The negative impact on dough and bread properties was more pronounced for freeze-dried powder. The result of the sensory study showed that wheat flour could be fortified by 1 g/100 g of leek powder without adverse effect on the consumer acceptability. Finally, the addition of leek powder did not impact the mould-free shelf-life of wheat bread.

The main objectives of this study were to investigate the antifungal activity of thyme essential oil (Thymus zygis) in-vitro and to validate its activity in par-baked wheat and sourdough bread (in-vivo) using the fungal strains Aspergillus niger and Penicillium paneum. The impact of thyme oil was evaluated in-vitro with the macro-dilution method with modified pH (4.8, 5.0, 5.5 & 6.0), aw (0.95 & 0.97) and temperature (22 & 30 °C) to mimic the conditions of wheat and sourdough par-baked bread stored at room temperature. Furthermore, the oil was applied in par-baked bread (0, 15 and 30 g sourdough/100 g dough). Challenge and shelf-life tests were performed to investigate the biopreservative potential of thyme oil in par-baked wheat and sourdough bread. Despite the promising in-vitro potential of thyme oil, no clear shelf-life extension was observed for par-baked bread which could be attributed to the oil. More research on food applications of essential oils is necessary to give the abundance of in-vitro studies industrial relevance. The use of sourdough, on the contrary, resulted in much more promising shelf-life extending properties. In both in-vitro as in-vivo assays, pH and aw showed no significant effect on fungal growth.

Sourdough is a very interesting natural preservation system to prolong mould free shelf-life of bread. Numerous studies have reported that the antifungal activity of sourdough is mainly correlated with the presence of lactic (LA) and acetic acid (AA), but very few information is available on the effect of undissociated acid concentrations in the aqueous phase of bread (C-HA; mmole/L). This study was conducted to provide additional information about the mode of action of the acids in sourdough bread, enabling a better shelf-life prediction. This study was divided into two parts. In part 1, three industrial biological sourdoughs were characterized (dough yield, pH, a(w), fermentation quotient, microbiota). During 7 weeks, a shelf-life test with natural flora was conducted with daily checks of visible mould growth (21 degrees C). In part 2, the effect of the acids present in the antifungal active sourdough breads was validated in chemically acidified wheat breads. Complete growth inhibition was observed in full-baked sourdough bread (30 g/100 g dough) containing Lactobacillus sanfranciscensis and Saccharomyces cerevisiae as dominant sourdough micro-organisms, whereas in control bread the shelf-life was limited to 4.4-9.2 days. These full-baked sourdough breads contained 36 mmole undissociated LA/L and 220 mmole undissociated AA/L. The data were used to make General Linear Regression models for shelf-life prediction and resulted in a fit of R-2 = 0.79 when expressing the shelf-life in function of C-HA,C- LA and C-HA,C-AA. In acidified breads, the role of lactic acid was not significant and only impacted shelf-life indirectly through acidification. No difference between antifungal activity of sourdough breads and chemically acidified bread with comparable C-HA,C- AA concentrations was observed. Shelf-life increased when 150-200 mmole undissociated AA/L aqueous phase in bread was present. To conclude, this study showed the importance of the undissociated acid fraction of acetic acid in relation to bread shelf-life, together with bread pH and moisture content.

EU regulation No. 1169/2011 states that foods that have been frozen and thawed before being sold, the name shall be accompanied by the designation ‘defrosted’. This requirement does not apply when defrosting has no negative impact on their safety and quality. Producers should be able to show that defrosting has no negative impact during the shelf-life. Therefore, the impact of temporary frozen storage on the quality and safety of industrially produced bakery products, including wholemeal bread, sandwich rolls, sponge cake and pie, was studied in comparison with non-frozen products. Total plate count, aw, texture analysis and sensory analysis were applied to assess microbial, physico-chemical quality and consumer acceptability of the products. All tests were performed before and after the defrosted shelf-life period. Freezing and defrosting of bakery products did not enhance microbial spoilage. All values remained under the maximal limit of microbial contamination, respectively 5 log CFU/g for bread products and 4 log CFU/g for sponge cake and pie. Texture analysis and aw showed only limited differences between fresh and defrosted products. Although a slight difference in texture was observed for sandwich rolls, sponge cake and pie through sensory trials, all products were found acceptable for consumption.

The main objectives were to investigate the antifungal effect of lactic (LA) and acetic acid (AA) and the fermentation quotient (FQ, mol/L ratio of LA over AA) towards Penicillium paneum and Aspergillus niger through growth/no-growth modelling of in-vitro data and to validate its effect in chemically acidified bread by performing challenge tests. Results have shown that AA has strong antifungal activity towards both bread moulds, albeit that P. paneum is ten times more resistant compared to A. niger. Complete growth inhibition of A. niger on chemically acidified bread was observed during 35 days at 21 °C for concentrations of AA ≥ 33 mmol/kg dough or ≥165 mmol undissociated AA/L water phase in bread. Whereas for A. niger the FQ must be close to zero and the concentration of AA in bread 33 mmol/kg dough to achieve complete growth inhibition, very high concentrations of AA and LA were needed to prevent growth of P. paneum (>100 mmol/kg dough). The acids also affected yeast activity in dough resulting in lower specific volumes and harder bread crumb. To conclude, the antifungal activity of the FQ cannot be generalized because its antifungal power depends on the sensitivity of the mould species towards LA and AA.