Sugar reduction in sweet bakery products: sourdough technology as a novel technological approach to overcome quality loss

Sugar reduction in food and beverages represents one of the major trends followed by consumers. Sugar is one factor, which promotes non-communicable diseases, such as type-2- diabetes, obesity and cardiovascular health issues. This doctoral dissertation, firstly, highlights the need for sugar reduction in bakery products in form of a literature review. Commonly known strategies, such as the replacement of sugar by bulking agents and artificial sweeteners, are discussed and the potential of sourdough technology to overcome techno-functional limitations is introduced. Several lactic acid bacteria and yeast strains are natural polyol producers and, furthermore, are able to produce exopolysaccharides, which makes sourdough a functional ingredient. The essential role of sugar is shown by the simple reduction of sugar by wheat starch, a non-sweet bulking agent, in a burger bun system. Sugar reduction increased specific volume (+0.99 ml/g) and changed the texture and structure of the burger buns significantly. Furthermore, sweetness intensity decreased, and microbial shelf life was shortened (-6 days). The replacement of sugar by commercially available polyols, such as xylitol, maltitol or mannitol, instead of wheat starch, revealed a significantly lower specific volume (-30 to -48%) and a harder crumb texture (+135% to +678%) compared to the full-sugar control. Moreover, polyols did not contribute to Maillard browning resulting in lighter crust colour. Among all polyols tested, mannitol showed the most promising results as a partial sugar replacer. An alternative approach to overcome quality loss during sugar reduction is the application of mannitol-rich sourdough. The heterofermentative lactic acid bacteria (LAB) strain Leuconostoc citreum TR116 was isolated from a yellow pea sourdough and characterised as a high mannitol producing strain. Wheat sourdough fermented with this LAB strain was performed with fructose addition, which was converted to mannitol (yield: 87%). The optimal fermentation time for high mannitol production was 30 h and mannitol-rich sourdough showed a production of metabolites in the ratio 1:0.34:0.15 (mannitol:lactate:actate). The incorporation of sourdough into a 50%-sugar-reduced burger bun system caused the same effect on gluten network development and viscoelastic properties, as the full-sugar control. Furthermore, no differences in specific volume and crumb hardness occurred, and mannitol-rich sourdough also contributed to sweetness and flavour. Additionally, a prolonged microbial shelf life was achieved. The addition of 10% mannitol-rich sourdough in a burger bun system is recommended. Since mannitol-rich sourdough could compensate quality loss in sugar-reduced burger buns, its effect on a 50% -sugar-reduced cake was investigated. Mannitol-rich sourdough increased the specific volume and softened the crumb texture (-8.6 N) of a 50%- sugar-reduced cake. Furthermore, it increased the sweetness intensity by 93% and contributed to aroma (+30%) and flavour (+25.5%). In sugar-reduced cakes a sourdough addition level of less than 10% is recommended. The positive impact of sourdough technology on buns and cakes led to the investigation of the effect of mannitol-rich sourdough in low-sugar biscuits. Since Leuconostoc citreum TR116 is a multifunctional strain, which is also able to produce exopolysaccharides, a mannitol-rich sourdough and a mannitol-rich sourdough with exopolysaccharides was fermented and incorporated in the biscuits. Sourdough addition caused an improvement in biscuit spreading and hardening. Furthermore, it contributed to colour and increased sweetness and flavour intensity (+140%, +139% respectively). It has to be noted that sourdough incorporation did not negatively influence the predicted glycemic index of low-sugar biscuits. The outcome of this research thesis provides a starting point for the development of sugar-reduced, low-sugar, or even no-sugar, highly consumer accepted bakery products using natural functional ingredients

Functionalisation of wheat and oat bran using single-strain fermentation and its impact on techno-functional and nutritional properties of biscuits

The adequate intake of dietary fbre is linked to several health benefts, for example, reducing the risk of non-communicable diseases, such as cardiovascular disease and diabetes. However, the population’s intake of dietary fbre is below the dosage recommended by the World Health Organisation. The incorporation of fbre ingredients, such as bran, in cereal based products afects the techno-functional and sensory properties, resulting in inferior product quality. To compensate quality loss, wheat bran (WB) and oat bran (OB) were fermented using the lactic acid bacterium strain Leuconostoc citreum TR116 prior to the application in a biscuit system. Two types of fermentation, one without any addition of sugars (FB) and one with the supplementation of 5% fructose and 5% sucrose to trigger the production of mannitol (FB+), were conducted and sugar and acid profles as well as pH and total titratable acids (TTA) were evaluated. Fermented WB showed a higher TTA (+58%) compared to fermented OB. Furthermore, FOB+resulted in higher microbial cell count and higher residual sugars after 48 h of fermentation. The application of fermented brans in a biscuit system showed a decrease in dough stickiness (− 41.7%) and an increase in dough hardness (+32%). The type of bran (WB and OB) as well as the type of fermentation (FB or FB+) infuenced the results of biscuit dough and biscuit quality (p<0.005). Fermentation increased biscuit spreading, infuenced biscuit snap force, enhanced crunchiness and colour formation, and lowered the predicted glycaemic index. Fermented OB (FOB+) resulted in a sensory profle comparable to the control

Functional properties of brewer’s spent grain protein isolate. The missing piece in the plant protein portfolio

Plant protein sources, as a part of developing sustainable food systems, are currently of interest globally. Brewer’s spent grain (BSG) is the most plentiful by-product of the brewing industry, representing ~85% of the total side streams produced. Although nutritionally dense, there are very few methods of upcycling these materials. High in protein, BSG can serve as an ideal raw material for protein isolate production. This study details the nutritional and functional characteristics of BSG protein isolate, EverPro, and compares these with the technological performance of the current gold standard plant protein isolates, pea and soy. The compositional characteristics are determined, including amino acid analysis, protein solubility, and protein profile among others. Related physical properties are determined, including foaming characteristics, emulsifying properties, zeta potential, surface hydrophobicity, and rheological properties. Regarding nutrition, EverPro meets or exceeds the requirement of each essential amino acid per g protein, with the exception of lysine, while pea and soy are deficient in methionine and cysteine. EverPro has a similar protein content to the pea and soy isolates, but far exceeds them in terms of protein solubility, with a protein solubility of ~100% compared to 22% and 52% for pea and soy isolates, respectively. This increased solubility, in turn, affects other functional properties; EverPro displays the highest foaming capacity and exhibits low sedimentation activity, while also possessing minimal gelation properties and low emulsion stabilising activity when compared to pea and soy isolates. This study outlines the functional and nutritional properties of EverPro, a brewer’s spent grain protein, in comparison to commercial plant protein isolates, indicating the potential for the inclusion of new, sustainable plant-based protein sources in human nutrition, in particular dairy alternative applications

From waste to taste. Application of fermented spent rootlet ingredients in a bread system

The process of upcycling and incorporating food by-products into food systems as functional ingredients has become a central focus of research. Barley rootlets (BR) are a by-product of the malting and brewing industries that can be valorised using lactic acid bacteria fermentation. This research investigates the effects of the inclusion of unfermented (BR-UnF), heat-sterilised (BR-Ster), and five fermented BR ingredients (using Weissella cibaria MG1 (BR-MG1), Leuconostoc citreum TR116 (BR-TR116), Lactiplantibacillus plantarum FST1.7 (BR-FST1.7), Lactobacillus amylovorus FST2.11 (BR-FST2.11), and Limosilactobacillus reuteri R29 (BR-R29) in bread. The antifungal compounds in BR ingredients and the impact of BR on dough rheology, gluten development, and dough mixing properties were analysed. Additionally, their effects on the techno-functional characteristics, in vitro starch digestibility, and sensory quality of bread were determined. BR-UnF showed dough viscoelastic properties and bread quality comparable to the baker's flour (BF). BR-MG1 inclusion ameliorated bread specific volume and reduced crumb hardness. Breads containing BR-TR116 had comparable bread quality to BF, while the inclusion of BR-R29 substantially slowed microbial spoilage. Formulations containing BR-FST2.11 and BR-FST1.7 significantly reduced the amounts of sugar released from breads during a simulated digestion and resulted in a sourdough-like flavour profile. This study highlights how BR fermentation can be tailored to achieve desired bread characteristics

Investigation of different dietary-fibre-ingredients for the design of a fibre enriched bread formulation low in FODMAPs based on wheat starch and vital gluten

Consumption of fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) often induces symptoms of irritable bowel syndrome (IBS). Since FODMAPs and dietary fbre (DF) share certain characteristics, IBS-patients have a limited intake of DF. Therefore, enrichment of a low FODMAP model bread (based on 84% wheat starch and 16% vital gluten) with various fbres (bamboo, cellulose, psyllium, guar gum) in two diferent concentrations (3 g/100 g and 6 g/100 g) was investigated. Physico-chemical properties of doughs and breads were analysed (fermentation quality, gluten development, specifc volume and hardness), as well as the release of reducing sugars during in vitro digestion. High performance anion exchange chromatography with coupled pulsed amperometric detection (HPAEC-PAD) was used to determine the FODMAP levels (contents of mannitol, sorbitol, fructose in excess of glucose, fructans and α-galactooligosaccharides) of both dough and bread. Prototypes were compared with wheat four-based breads (bakers’ four with and without wheat bran addition) to assess the performance of these prototypes. Prototypes showed a decreased quality compared to a baker’s four control, however, a quality comparable to commercial wheat bran breads was found. This in combination with a lower release of reducing sugars during in vitro digestion underline the potential of fbre enriched breads as part of a healthier and more palateable low FODMAP diet. Furthermore, this study highlights the importance of the type (viscous and insoluble) and the concentration of fbres used. Application of psyllium in a concentration of 3 g/100 g showed the most benefcial impact on both physical (specifc volume, hardness after 0 h and 24 h) and nutritional aspects of bread

Evaluation of a new method to determine the water addition level in gluten-free bread systems

The water content in gluten-free recipes plays an essential role in the resulting product quality. Up to date the water adjustment is conducted mainly by trial-and-error. Brabender GmbH & Co. KG developed an attachment for the Farinograph, which makes the measurement of batter consistencies feasible. The water content was adjusted using this new tool and compared to the water determined based on the water hydration capacity (WHC) of the single bulking ingredients. Furthermore, bread quality characteristics were analysed. Five different hydrocolloids were tested in a gluten-free system based on rice flour. Water levels differed significantly, when guar gum (20% water) or sodium alginate (18% water) were incorporated. The use of Farinograph resulted generally in a higher specific volume (+0.63 ml/g) and a softer crumb (−16 N). On the contrary, the WHC-method only gave an indication about the water addition but did not consider temperature changes during mixing and its effect on the hydration. In conclusion, Farinograph can be considered as a useful tool for the determination of the optimal water content, and additionally provides useful information about batter stability and dough development time

Nutritional properties and health aspects of pulses and their use in plant-based yogurt alternatives

Plant-based yogurt alternatives are increasing in market value, while dairy yogurt sales are stagnating or even declining. The plant-based yogurt alternatives market is currently dominated by products based on coconut or soy. Coconut-based products especially are often low in protein and high in saturated fat, while soy products raise consumer concerns regarding genetically modified soybeans, and soy allergies are common. Pulses are ideally suited as a base for plant-based yogurt alternatives due to their high protein content and beneficial amino acid composition. This review provides an overview of pulse nutrients, pro-nutritional and anti-nutritional compounds, how their composition can be altered by fermentation, and the chemistry behind pulse protein coagulation by acid or salt denaturation. An extensive market review on plant-based yogurt alternatives provides an overview of the current worldwide market situation. It shows that pulses are ideal base ingredients for yogurt alternatives due to their high protein content, amino acid composition, and gelling behavior when fermented with lactic acid bacteria. Additionally, fermentation can be used to reduce anti-nutrients such as a-galactosides and vicine or trypsin inhibitors, further increasing the nutritional value of pulse-based yogurt alternatives

Barley protein properties, extraction and applications, with a focus on brewers’ spent grain protein

Barley is the most commonly used grain in the brewing industry for the production of beer-type beverages. This review will explore the extraction and application of proteins from barley, particularly those from brewers’ spent grain, as well as describing the variety of proteins present. As brewers’ spent grain is the most voluminous by-product of the brewing industry, the valorisation and utilisation of spent grain protein is of great interest in terms of sustainability, although at present, BSG is mainly sold cheaply for use in animal feed formulations. There is an ongoing global effort to minimise processing waste and increase up-cycling of processing side-streams. However, sustainability in the brewing industry is complex, with an innate need for a large volume of resources such as water and energy. In addition to this, large volumes of a by-product are produced at nearly every step of the process. The extraction and characterisation of proteins from BSG is of great interest due to the high protein quality and the potential for a wide variety of applications, including foods for human consumption such as bread, biscuits and snack-type products

Brewer’s spent yeast (BSY), an underutilized brewing by-product

The repurposing of by-products and the reduction of waste from food processing streams is an ever-increasing area of interest. Brewer’s spent yeast (BSY) is a prevalent by-product of the brewing industry. The spent yeast cells are removed at the end of the bulk fermentation. A small amount of it is used to start the next batch of fermentation; however, the majority of the spent yeast is discarded. This discarded yeast is high in nutrients, in particular proteins, vitamins and minerals, as well as containing functional and biologically active compounds such as polyphenols, antioxidants, β-glucans and mannoproteins. At present, BSY is mainly used in animal feed as a cheap and readily available source of protein. This review explores alternative, value-added applications for brewer’s spent yeast including nutritional ingredients, functional food additives as well as non-food applications. A major challenge in the utilization of BSY in food for human consumption is the high level of RNA. An excess of RNA in the diet can lead to an increase in uric acid in the bloodstream, potentially causing painful health conditions like gout. This issue can be overcome by RNA degradation and removal via additional treatment, namely heat treatment and enzymatic treatment. There is potential for the use of BSY ingredients in various food applications, including meat substitutes, bakery products and savory snacks

Fermentation as a tool to revitalise brewers' spent grain and elevate techno-functional properties and nutritional value in high fibre bread

Recycling of by-products from the food industry has become a central part of research to help create a more sustainable future. Brewers' spent grain is one of the main side-streams of the brewing industry, rich in protein and fibre. Its inclusion in bread, however, has been challenging and requires additional processing. Fermentation represents a promising tool to elevate ingredient functionality and improve bread quality. Wheat bread was fortified with spray-dried brewers' spent grain (BSG) and fermented brewers' spent grain (FBSG) at two addition levels to achieve "source of fibre" and "high in fibre" claims according to EU regulations. The impact of BSG and FBSG on bread dough, final bread quality and nutritional value was investigated and compared to baker's flour (BF) and wholemeal flour (WMF) breads. The inclusion of BSG and FBSG resulted in a stronger and faster gluten development; reduced starch pasting capacity; and increased dough resistance/stiffness. However, fermentation improved bread characteristics resulting in increased specific volume, reduced crumb hardness and restricted microbial growth rate over time. Additionally, the inclusion of FBSG slowed the release in reducing sugars over time during in vitro starch digestion. Thus, fermentation of BSG can ameliorate bread techno-functional properties and improve nutritional quality of breads