Claudia Axel

Antifungal sourdough lactic acid bacteria as biopreservation tool in quinoa and rice bread.

The use of sourdough fermented with specific strains of antifungal lactic acid bacteria can reduce chemical preservatives in bakery products. The main objective of this study was to investigate the production of antifungal carboxylic acids after sourdough fermentation of quinoa and rice flour using the antifungal strains Lactobacillus reuteri R29 and Lactobacillus brevis R2Δ as bioprotective cultures and the non-antifungal L. brevis L1105 as a negative control strain. The impact of the fermentation substrate was evaluated in terms of metabolic activity, acidification pattern and quantity of antifungal carboxylic acids. These in situ produced compounds (n=20) were extracted from the sourdough using a QuEChERS method and detected by a new UHPLC-MS/MS chromatography. Furthermore, the sourdough was applied in situ using durability tests against environmental moulds to investigate the biopreservative potential to prolong the shelf life of bread. Organic acid production and TTA values were lowest in rice sourdough. The sourdough fermentation of the different flour substrates generated a complex and significantly different profile of carboxylic acids. Extracted quinoa sourdough detected the greatest number of carboxylic acids (n=11) at a much higher concentration than what was detected from rice sourdough (n=9). Comparing the lactic acid bacteria strains, L. reuteri R29 fermented sourdoughs contained generally higher concentrations of acetic and lactic acid but also the carboxylic acids. Among them, 3-phenyllactic acid and 2-hydroxyisocaproic acid were present at a significant concentration. This was correlated with the superior protein content of quinoa flour and its high protease activity. With the addition of L. reuteri R29 inoculated sourdough, the shelf life was extended by 2 days for quinoa (+100%) and rice bread (+67%) when compared to the non-acidified controls. The L. brevis R2Δ fermented sourdough bread reached a shelf life of 4 days for quinoa (+100%) and rice (+33%). However, the shelf life was similar to the chemically acidified control indicating that the preservation effect of the carboxylic acids seems to have a minor contribution effect on the antifungal activity in gluten-free breads.

Ecofriendly control of potato late blight causative agent and the potential role of lactic acid bacteria: a review

In times of increasing societal pressure to reduce the application of pesticides on crops, demands for environmentally friendly replacements have intensified. In the case of late blight, a devastating potato plant disease, the historically most widely known plant destroyer has been the oomycete Phytophthora infestans. To date, the most important strategy for control of this pathogen has been the frequent application of fungicides. Due to the aforementioned necessity to move away from traditional chemical treatments, many studies have focused on finding alternative ecofriendly biocontrol systems. In general, due to the different modes of actions (i.e. antagonistic effects or induction of plant defence mechanisms), the use of microorganisms as biological control agents has a definite potential. Amongst them, several species of lactic acid bacteria have been recognised as producers of bioactive metabolites which are functional against a broad spectrum of undesirable microorganisms, such as fungi, oomycetes and other bacteria. Thus, they may represent an interesting tool for the development of novel concepts in pest management. This review describes the present situation of late blight disease and summarises current literature regarding the biocontrol of the phytopathogen P. infestans using antagonistic microorganisms.

Mould spoilage of bread and its biopreservation: A review of current strategies for bread shelf life extension

ABSTRACT Microbial spoilage of bread and the consequent waste problem causes large economic losses for both the bakery industry and the consumer. Furthermore the presence of mycotoxins due to fungal contamination in cereals and cereal products remains a significant issue. The use of conventional chemical preservatives has several drawbacks, necessitating the development of clean-label alternatives. In this review, we describe current research aiming to extend the shelf life of bread through the use of more consumer friendly and ecologically sustainable preservation techniques as alternatives to chemical additives. Studies on the in situ-production/-expression of antifungal compounds are presented, with special attention given to recent developments over the past decade. Sourdough fermented with antifungal strains of lactic acid bacteria (LAB) is an area of increasing focus and serves as a high-potential biological ingredient to produce gluten-containing and gluten-free breads with improved nutritional value, quality and safety due to shelf-life extension, and is in-line with consumers demands for more products containing less additives. Other alternative biopreservation techniques include the utilization of antifungal peptides, ethanol and plant extracts. These can be added to bread formulations or incorporated in antimicrobial films for active packaging (AP) of bread. This review outlines recent progress that has been made in the area of bread biopreservation and future perspectives in this important area.

Quantification of cyclic dipeptides from cultures of Lactobacillus brevis R2Δ by HRGC/MS using stable isotope dilution assay

Lactic acid bacteria (LAB) play an important role as natural preservatives in fermented food and beverage systems, reducing the application of chemical additives. Thus, investigating their antifungal compounds, such as cyclic dipeptides, has gained prominence. Previous research has primarily focussed on isolation of these compounds. However, their precise quantification will provide further information regarding their antifungal performance in a complex system. To address this, deuterated labelled standards of the cyclic dipeptides cyclo(Leu-Pro), cyclo(Pro-Pro), cyclo(Met-Pro) and cyclo(Phe-Pro) were synthesized, and stable isotope dilution assays were developed, enabling an accurate quantification of cyclo(Leu-Pro), cyclo(Pro-Pro), cyclo(Met-Pro) and cyclo(Phe-Pro) in MRS-broth and wort. Quantitative results showed that, in the Lactobacillus brevis R2Δ fermented MRS-broth, the concentrations of cyclo(Leu-Pro), cyclo(Pro-Pro) and cyclo(Phe-Pro) were significantly higher (P < 0.05), than in wort for cyclo (Leu-Pro) when compared with their controls. This indicates that the formation of these three cyclic dipeptides is related to L. brevis R2Δ metabolism. Furthermore, this represents the first report of cyclic dipeptides quantification using stable isotope dilution assays in LAB cultures both in vitro and in a food system.

Correlation of Flavor Profile to Sensory Analysis of Bread Produced with Different Saccharomyces cerevisiae Originating from the Baking and Beverage Industry

Aroma is an important quality parameter for wheat bread, and most of the aroma compounds in yeast-fermented bread are caused by the fermentative action of yeast. In this study, the impact of various strains of Saccharomyces cerevisiae, originating from the beverage industry, were investigated on the aroma profile of wheat bread. Seven volatiles were analyzed by gas chromatography–mass spectrometry after thermal desorption (GC-MS TD) from the bread crumb. The results showed yeast strain-dependent production of aroma compounds. Descriptive sensory analysis resulted in an overall taste acceptance by the panelists for breads baked with S. cerevisiae baker’s yeast, T-58, and Blanc. The panel acceptance can be explained by the production of sensory-active compounds such as 3-methyl-1-butanol and 2,3-butandiol. Furthermore, the panelists preferred bread samples with a less bitter (r = –0.934, P < 0.01) and less cheesy taste (r = –0.865, P < 0.03). Also the visual aspects play an important role, shown by correlat...

Effect of salt reduction on wheat-dough properties and quality characteristics of puff pastry with full and reduced fat content

Puff pastry is a major contributor of fat and sodium intake in many countries. The objective of this research was to determine the impact of salt (0-8.4g/100g flour) on the structure and quality characteristics of puff pastry with full and reduced (-40%) fat content as well as the rheological properties of the resulting dough. Therefore, empirical rheological tests were carried out including dough extensibility, dough stickiness and GlutoPeak test. The quality of the puff pastry was characterized with the VolScan, Texture Analyzer and C-Cell. NaCl reduction significantly changed rheological properties of the basic dough as well as a number of major quality characteristics of the puff pastry. Significant differences due to NaCl addition were found in particular for dough resistance, dough stickiness, Peak Maximum Time and Maximum Torque (p<0.05). Peak firmness and total firmness decreased significantly (p<0.05) with increasing salt levels for puff pastry containing full fat. Likewise, maximal lift, specific volume, number of cells and slice brightness increased with increasing NaCl at both fat levels. Although a sensorial comparison of puff pastries revealed that salt reduction (30%) was perceptible, no significant differences were found for all other investigated attributes. Nevertheless, a reduction of 30% salt and 40% fat in puff pastry is achievable as neither the perception and visual impression nor attributes such as volume, firmness and flavour of the final products were significantly affected.

Xylitol, mannitol and maltitol as potential sucrose replacers in burger buns

Burger buns are a source of added sugar, containing 7-12%, in order to ensure their unique texture and taste. Hence, suitable sugar substitutes for burger buns are urgently needed. This study aimed to elucidate the effect of three different polyols on dough and product quality of burger buns. Xylitol, mannitol and maltitol were incorporated individually in a burger bun system, by replacing added sucrose by 30%, 50% and 100%. Wheat starch was used to compare the impact of polyols with another non-sweet bulking agent. The effects on dough properties as well as on the burger buns themselves were investigated. Compared to sugar-rich doughs, polyols lowered the fermentation quality, resulting in lower dough development (-37 to -81%) and poorer gaseous release (-62 to -87%). Furthermore, a delay in gluten network development (+50 to +161%) and a decrease in extensibility (-14 to -18%) with increasing concentrations were detected. Interestingly, maltitol and xylitol did not affect the pasting properties, whereas mannitol increased pasting temperature (+15 °C). Moreover, polyols did not influence the viscoelastic properties of the dough. The incorporation of sugar alcohols led to a significant decrease in specific volume (-30 to -48%), and to a harder crumb texture (+135 to +678%). Moreover, the L*-value increased with increasing amount of polyols, resulting in a very pale crust colour. In conclusion, a reduction of 50% added sucrose by polyols was applicable, whereas mannitol was the most suitable sugar replacer amongst the polyols tested.

Sodium Chloride and Its Influence on the Aroma Profile of Yeasted Bread

The impact of sodium chloride (NaCl) concentration on the yeast activity in bread dough and its influence on the aroma profile of the baked bread was investigated. Key aroma compounds in the bread samples were analysed by two-dimensional high-resolution gas chromatography-mass spectrometry in combination with solvent-assisted flavour evaporation distillation. High-sensitivity proton-transfer-reaction mass spectrometry was used to detect and quantify 2-phenylethanol in the headspace of the bread dough during fermentation. The analyses revealed significant (p < 0.05) changes in the aroma compounds 2-phenylethanol, (E)-2-nonenal, and 2,4-(E,E)-decadienal. Descriptive sensory analysis and discriminating triangle tests revealed that significant differences were only determinable in samples with different yeast levels but not samples with different NaCl concentrations. This indicates that a reduction in NaCl does not significantly influence the aroma profile of yeasted bread at levels above the odour thresholds of the relevant compounds, thus consumers in general cannot detect an altered odour profile of low‑salt bread crumb.

Optimization of Fat-Reduced Puff Pastry Using Response Surface Methodology

Puff pastry is a high-fat bakery product with fat playing a key role, both during the production process and in the final pastry. In this study, response surface methodology (RSM) was successfully used to evaluate puff pastry quality for the development of a fat-reduced version. The technological parameters modified included the level of roll-in fat, the number of fat layers (50–200) and the final thickness (1.0–3.5 mm) of the laminated dough. Quality characteristics of puff pastry were measured using the Texture Analyzer with an attached Extended Craft Knife (ECK) and Multiple Puncture Probe (MPP), the VolScan and the C-Cell imaging system. The number of fat layers and final dough thickness, in combination with the amount of roll-in fat, had a significant impact on the internal and external structural quality parameters. With technological changes alone, a fat-reduced (≥30%) puff pastry was developed. The qualities of fat-reduced puff pastries were comparable to conventional full-fat (33 wt %) products. A sensory acceptance test revealed no significant differences in taste of fatness or ‘liking of mouthfeel’. Additionally, the fat-reduced puff pastry resulted in a significant (p < 0.05) positive correlation to ‘liking of flavor’ and overall acceptance by the assessors.

Modulation of in vitro predicted glycaemic index of white wheat bread by different strains of Saccharomyces cerevisiae originating from various beverage applications

A low glycaemic index (GI) in bakery products can be associated with a decrease of cardiovascular disease and a protective role against the development and management of non-insulin-dependent diabetes. In this study, the impact of different Saccharomyces cerevisiae strains applied to the bread-making process on the GI of bread was investigated. The GI was measured using an in vitro enzymatic model system in relation to the metabolic patterns of the different yeast strains and the compositional analysis of the breads. Although total and resistant starch contents of the breads were similar, a significant reduction in GI was obtained for breads fermented with S. cerevisiae s-23, wb-06 and Blanc. Differences in the amount of protein and fat were observed. However, their proportion when related to carbohydrate content was not high enough to effectively alter the GI of the breads. Considering the fermentation process, S. cerevisiae wb-06, Blanc and to some extent s-23 were characterised by slower fermentation rates. The resulting breads were reduced in GI with lower specific volumes as well as firmer crumb structures. Breads high in GI were either characterised by an increased glucose content (S. cerevisiae us-05) or high specific bread volumes and soft crumbs (S. cerevisiae Baker’s yeast and T-58) indicating a relationship between complete starch gelatinisation during baking and starch digestibility. Conclusively, the GI of white wheat bread can be significantly decreased using different strains from the species S. cerevisiae.