Ingredient Functionality During Foam-Type Cake Making: A Review.

Foam-type cakes are complex food systems. Their main ingredients are wheat flour, hen eggs, sugar, leavening agent, and, in some cases, oil and/or surfactants. In contrast to the vast amount of research outcomes on the contribution of ingredients to the quality of batter-type cake systems, information on the functionality and importance of the ingredients and their constituents in foam-type cake systems is lacking. This review defines foam-type cakes, describes how they are made, summarizes the current knowledge of factors determining their quality, and identifies the current knowledge gaps.

Conditions Governing Food Protein Amyloid Fibril Formation-Part I: Egg and Cereal Proteins.

Conditions including heating mode, time, temperature, pH, moisture and protein concentration, shear, and the presence of alcohols, chaotropic/reducing agents, enzymes, and/or salt influence amyloid fibril (AF) formation as they can affect the accessibility of amino acid sequences prone to aggregate. As some conditions applied on model protein resemble conditions in food processing unit operations, we here hypothesize that food processing can lead to formation of protein AFs with a compact cross ß-sheet structure. This paper reviews conditions and food constituents that affect amyloid fibrillation of egg and cereal proteins. While egg and cereal proteins often coexist in food products, their impact on each other's fibrillation remains unknown. Hen egg ovalbumin and lysozyme form AFs when subjected to moderate heating at acidic pH separately. AFs can also be formed at higher pH, especially in the presence of alcohols or chaotropic/reducing agents. Tryptic wheat gluten digests can form fibrillar structures at neutral pH and maize and rice proteins do so in aqueous ethanol or at acidic pH, respectively.

Conditions Governing Food Protein Amyloid Fibril Formation. Part II: Milk and Legume Proteins.

Both intrinsic and extrinsic factors impact amyloid formation of food proteins. We here review the impact of various conditions and food constituents on amyloid fibrillation of milk and legume proteins. Much less is known about casein and legume protein amyloid-like fibril formation than about that of whey proteins such as ß-lactoglobulin, α-lactalbumin, and bovine serum albumin. Proteins of both sources are often studied after heating under strong acidic (pH < 3) conditions. The latter induces changes in protein conformation and often peptide hydrolysis. At higher pH values, alcohols, chaotropic and/or reducing agents induce the conformational changes required to enhance fibrillation. Different types of food proteins can impact each other's fibrillation. Also, the presence of other food constituents can enhance or reduce it. No general conclusions on the mechanisms or impact of different food constituents on food proteins can be made. Optimal conditions for AF formation, that is, heating for several days at low pH, are rare in food processing. However, this does not exclude the possibility of AF formation in food products. For example, slow cooking of hydrolyzed proteins may enhance it. Future research should focus on the prevalence of AFs in complex food systems or model systems relevant for food processing.

Rational Design of Amyloid-Like Fibrillary Structures for Tailoring Food Protein Techno-Functionality and Their Potential Health Implications.

To control and enhance protein functionality is a major challenge for food scientists. In this context, research on food protein fibril formation, especially amyloid fibril formation, holds much promise. We here first provide a concise overview of conditions, which affect amyloid formation in food proteins. Particular attention is directed towards amyloid core regions because these sequences promote ordered aggregation. Better understanding of this process will be key to tailor the fibril formation process. Especially seeding, that is, adding preformed protein fibrils to protein solutions to accelerate fibril formation holds promise to tailor aggregation and fibril techno-functionality. Some studies have already indicated that food protein fibrillation indeed improves their techno-functionality. However, much more research is necessary to establish whether protein fibrils are useful in complex food systems and whether and to what extent they resist food processing unit operations. In this review the effect of amyloid formation on gelation, interfacial properties, foaming, and emulsification is discussed. Despite their prevalent role as functional structures, amyloids also receive a lot of attention due to their association with protein deposition diseases, prompting us to thoroughly investigate the potential health impact of amyloid-like aggregates in food. A literature review on the effect of the different stages of the human digestive process on amyloid toxicity leads us to conclude that food-derived amyloid fibrils (even those with potential pathogenic properties) very likely have minimal impact on human health. Nevertheless, prior to wide-spread application of the technology, it is highly advisable to further verify the lack of toxicity of food-derived amyloid fibrils.

Ingredient Functionality in Multilayered Dough-margarine Systems and the Resultant Pastry Products: A Review.

Pastry products are produced from heterogeneous multilayered dough systems. The main ingredients are flour, water, fat and sugar for puff pastry, and the same plus yeast for fermented pastry. Key aspects in pastry production are (i) building laminated dough containing alternating layers of dough and bakery fat and (ii) maintaining this multilayered structure during processing to allow for steam entrapment for proper dough lift during baking. Although most authors agree on the importance of gluten and fat for maintaining the integrity of the different layers, detailed studies on their specific function are lacking. The exact mechanism of steam entrapment during dough lift and the relative contribution of water set free from the fat phase during baking also remain unclear. This review brings together current knowledge on pastry products and the factors determining (intermediate) product quality. Its focus is on flour constituents, fat, water, and (where applicable) yeast during the different production stages of pastry products. Future research needs are addressed as the knowledge on biochemical and physical changes occurring in flour constituents and other ingredients during pastry production and their effect on product quality is currently inadequate.

Relevance of the Functional Properties of Enzymatic Plant Protein Hydrolysates in Food Systems.

Proteins play a crucial role in determining texture and structure of many food products. Although some animal proteins (such as egg white) have excellent functional and organoleptic properties, unfortunately, they entail a higher production cost and environmental impact than plant proteins. It is rather unfortunate that plant protein functionality is often insufficient because of low solubility in aqueous media. Enzymatic hydrolysis strongly increases solubility of proteins and alters their functional properties. The latter is attributed to 3 major structural changes: a decrease in average molecular mass, a higher availability of hydrophobic regions, and the liberation of ionizable groups. We here review current knowledge on solubility, water- and fat-holding capacity, gelation, foaming, and emulsifying properties of plant protein hydrolysates and discuss how these properties are affected by controlled enzymatic hydrolysis. In many cases, research in this field has been limited to fairly simple set-ups where functionality has been assessed in model systems. To evolve toward a more widely applied industrial use of plant protein hydrolysates, a more thorough understanding of functional properties is required. The structure-function relationship of protein hydrolysates needs to be studied in depth. Finally, test model systems closer to real food processing conditions, and thus to real foods, would be helpful to evaluate whether plant protein hydrolysates could be a viable alternative for other functional protein sources.

Natural Additives in Wheat-Based Pasta and Noodle Products: Opportunities for Enhanced Nutritional and Functional Properties.

Pasta products and noodles have been staple foods since ancient times in many countries all over the world. These cereal products are still increasingly popular worldwide for their convenience, nutritional properties, special flavor, and taste. Pasta and noodles are essentially the same type of food but differ in their raw materials and shaping process, as well as the people and regions in the world consuming them. Many additives have been developed and are being used today in pasta and noodle products for various purposes. However, due to lack of knowledge about specific uses for some additives, they are sometimes misused by manufacturers. This can lead to opposite technological effects instead and may even cause damage to human health. Due to consumer demands, interest now focuses on natural "green" food additives with broad-spectrum functions, high effectiveness, and low toxicity. In order to provide detailed references for noodle and pasta production, as well as to provide ideas for developing new types of these products, here we summarize the types of natural additives that are being incorporated in pasta and noodle products, mainly for quality improvement and food preservation.

The effect of ultrasound on the extraction and foaming properties of proteins from potato trimmings.

High-intensity ultrasonication is an emerging technology for plant protein isolation and modification. In this study, the potential of temperature-controlled ultrasonication to enhance the recovery of functional proteins from potato trimmings was assessed. Different ultrasound energy levels [2000-40,000 J/g fresh weight (FW)] were applied during protein extraction at pH 9.0. True protein yields after ultrasonication significantly increased (up to 91%) compared to conventional extraction (33%). Microstructural analysis of the extraction residues showed more disrupted cells as ultrasonication time increased. Ultrasound treatments (10,000 and 20,000 J/g FW) increased the protein yield without affecting the foaming and air-water interfacial properties of protein isolates obtained after isoelectric precipitation (pH 4.0). However, proteins obtained after extended ultrasonication (40,000 J/g FW) had significantly slower early-stage adsorption kinetics. This was attributed to ultrasound-induced aggregation of the protease inhibitor fraction. In conclusion, ultrasonication shows potential to help overcome some challenges associated with plant protein extraction.

Extractability and chromatographic separation of proteins from potato (Solanum tuberosum L.) trimmings.

By-products from the potato processing industry, like potato trimmings, are sustainable sources of proteins. Here, a size-exclusion high performance liquid chromatography (SE-HPLC) method was applied to simultaneously determine the extractability and aggregation state of proteins from three batches of potato trimmings of different cultivars. Obtained SE-HPLC profiles allowed distinguishing between the patatin and protease inhibitor fractions of potato proteins. Moreover, only 75% of the crude proteins could be extracted in phosphate buffer containing sodium dodecyl sulfate and a reducing agent, indicating the presence of physical extraction barriers. Ball milling for 5 min significantly increased protein extractability, but prolonged treatment resulted in aggregation of native patatin and a reduced protein extractability. Microwave-dried trimmings had a lower protein extractability than freeze-dried trimmings. In future research, the SE-HPLC method can be used to examine changes in potato protein (fractions) as a result of processing.

Varying precipitation conditions allow directing the composition and physical properties of soy protein concentrates.

Soy protein concentrates (SPCs) are common food ingredients. They typically contain 65% (w/w) protein and ∼30% (w/w) carbohydrate. SPCs can be obtained with various protein precipitation conditions. A systematic study of the impact of these different protein precipitation protocols on the SPC protein composition and physical properties is still lacking. Here, SPCs were prepared via three different protocols, that is, isoelectric (pH 3.5-5.5), aqueous ethanol (50%-70% [v/v]), and Ca2+ ion (5-50 mM) based precipitations, and analyzed for (protein) composition, protein thermal properties, dispersibility, and water-holding capacity. SPCs precipitated at pH 5.5 or by adding 15 mM Ca2+ ions had a lower 7S/11S globulin ratio (∼0.40) than that (∼0.50) of all other SPC samples. Protein in SPCs obtained by isoelectric precipitation denatured at a significantly higher temperature than those in ethanol- or Ca2+ -precipitated SPCs. Precipitation with 50%-60% (v/v) ethanol resulted in pronounced denaturation of 2S albumin and 7S globulin fractions in SPCs. Additionally, increasing the precipitation pH from 3.5 to 5.5 and increasing the Ca2+ ion concentration from 15 to 50 mM caused a strong decrease of both the dispersibility of the protein in SPC and its water-holding capacity at pH 7.0. In conclusion, this study demonstrates that the SPC production process can be directed to obtain ingredients with versatile protein physicochemical properties toward potential food applications. PRACTICAL APPLICATION: This study demonstrates that applying different protein precipitation protocols allows obtaining SPCs that vary widely in (protein) composition and physical properties (such as protein dispersibility and water-holding capacity). These varying traits can greatly influence the suitability of SPCs as functional ingredients for specific applications, such as the production of food foams, emulsions, gels, and plant-based meat alternatives. The generated knowledge may allow targeted production of SPCs for specific applications.

Sucrose substitution in cake systems is not a piece of cake.

Successful sucrose replacement in cake systems requires thorough understanding of its functionality. Time-domain 1H NMR showed that water in the viscous aqueous phase isolated from cake batter by ultracentrifugation [i.e. the batter liquor (BL)] exhibits low mobility by its low T2 relaxation time (T2,D RT). This is due to its interactions with sucrose or sucrose replacers. The T2,D RT itself is positively related with the effective volumetric hydrogen bond density of sucrose or sucrose replacers. Sucrose additionally co-determines the quantity and viscosity of cake BL and thereby how much air the batter contains at the end of mixing. Like sucrose, maltitol and oligofructose provide adequate volumes of BL with low water mobility and thus sufficient air in the batter, while the rather insoluble mannitol and inulin do not. Differential scanning calorimetry and rapid viscosity analysis revealed, however, that, in contrast to sucrose and maltitol, oligofructose fails to provide appropriate timings of starch gelatinisation and protein denaturation, resulting in poor cake texture. The shortcomings of mannitol and oligofructose in terms of respectively ensuring appropriate gas content in batter and biopolymer transitions during baking can be overcome by using mixtures thereof. This work shows that successful sucrose substitutes or substitute mixtures must provide sufficient BL with low water mobility and ensure appropriate timings of starch and protein biopolymer transitions during baking.

Study of the Fermentation Characteristics of Non-Conventional Yeast Strains in Sweet Dough.

Despite the diverse functions of yeast, only a relatively homogenous group of Saccharomyces cerevisiae yeasts is used in the baking industry. Much of the potential of the natural diversity of yeasts has not been explored, and the sensory complexity of fermented baked foods is limited. While research on non-conventional yeast strains in bread making is increasing, it is minimal for sweet fermented bakery products. In this study, the fermentation characteristics of 23 yeasts from the bakery, beer, wine, and spirits industries were investigated in sweet dough (14% added sucrose w/w dm flour). Significant differences in invertase activity, sugar consumption (0.78-5.25% w/w dm flour), and metabolite (0.33-3.01% CO2; 0.20-1.26% ethanol; 0.17-0.80% glycerol; 0.09-0.29% organic acids) and volatile compound production were observed. A strong positive correlation (R2 = 0.76, p < 0.001) between sugar consumption and metabolite production was measured. Several non-conventional yeast strains produced more positive aroma compounds and fewer off-flavors than the reference baker's yeast. This study shows the potential of non-conventional yeast strains in sweet dough.

Impact of process parameters on the specific volume of wholemeal wheat bread made using sourdough- and baker's yeast-based leavening strategies.

The final quality of wholemeal wheat bread is determined by the process parameter settings and leavening strategy. We hypothesise that the used leavening strategy may influence the optimal process parameter settings and, as such, the specific volume of the bread loaf. To analyse this interaction, bread was leavened with (i) a type 1 sourdough (SB), (ii) a type 1 sourdough combined with baker's yeast (YSB), or (iii) baker's yeast (YB). For each leavening strategy, the specific volume of bread, in response to variations in mixing time (4-10/4-14 min), water absorption (60-85 %), and proofing time (1-7/1-3 h), was analysed using an I-optimal response surface experimental design. Data modelling identified a substantially lower maximal specific volume of SB (2.13 mL/g), compared to YSB (3.30 mL/g) and YB (3.26 mL/g). The proofing time and water absorption mostly influenced the specific volume of the SB and YSB, respectively. However, the mixing and proofing times mainly affected the specific volume of YB. The type 1 sourdough reduced the mixing time and water absorption required for an optimal specific volume of bread compared to baker's yeast. These results challenge the idea of yielding higher volumes upon using sourdough compared to baker's yeast and highlight the importance of optimisation of bread dough formulations and breadmaking processes.

Cross-linking of wheat gluten proteins during production of hard pretzels.

The impact of the hot alkaline dip, prior to pretzel-baking, on the types and levels of cross-links between wheat proteins was studied. Protein extractability of pretzel dough in sodium dodecyl sulfate containing buffer decreased during alkaline dipping [45 s, 1.0% (w/v) NaOH, 90°C], and even more during baking (3 min at 250°C) and drying (10 min at 135°C). Reducing agent increased the extractability partly, indicating that both reducible (disulfide, SS) and non-reducible (non-SS) protein cross-links had been formed. The decrease in cystine levels suggested ß-elimination of cystine releasing Cys and dehydroalanine (DHA). Subsequent reaction of DHA with Lys and Cys, induced the unusual and potentially cross-linking amino acids lysinoalanine (LAL) and lanthionine (LAN), respectively, in alkaline dipped dough (7 µmol LAN/g protein) and in the end product (9 µmol LAL and 50 µmol LAN/g protein). The baking/drying step increased sample redness, decreased Lys levels more than expected based on LAL formation (57 µmol/g protein), and induced a loss of reducing sugars (99 µmol/g protein), which suggested the potential contribution of Maillard-derived cross-links to the observed extractability loss. However, levels of Maillard products which possibly cross-link proteins, are small compared to DHA-derived cross-links. Higher dipping temperatures, longer dipping times, and higher NaOH concentrations increased protein extractability losses and redness, as well as LAL and LAN levels in the end product. No indications for Maillard-derived cross-links or LAL in pretzel dough immediately after dipping were found, even when severe dipping conditions were used.

Sugar Levels Determine Fermentation Dynamics during Yeast Pastry Making and Its Impact on Dough and Product Characteristics.

Fermented pastry products are produced by fermenting and baking multi-layered dough. Increasing our knowledge of the impact of the fermentation process during pastry making could offer opportunities for improving the production process or end-product quality, whereas increasing our knowledge on the sugar release and consumption dynamics by yeast could help to design sugar reduction strategies. Therefore, this study investigates the impact of yeast fermentation and different sugar concentrations on pastry dough properties and product quality characteristics. First, yeasted pastry samples were made with 8% yeast and 14% sucrose on a wheat flour dry matter base and compared to non-yeasted samples. Analysis of saccharide concentrations revealed that sucrose was almost entirely degraded by invertase in yeasted samples after mixing. Fructans were also degraded extensively, but more slowly. At least 23.6 ± 2.6% of the released glucose was consumed during fermentation. CO2 production during fermentation contributed more to product height development than water and ethanol evaporation during baking. Yeast metabolites weakened the gluten network, causing a reduction in dough strength and extensibility. However, fermentation time had a more significant impact on dough rheology parameters than the presence of yeast. In balance, yeast fermentation did not significantly affect the calculated sweetness factor of the pastry product with 14% added sucrose. Increasing the sugar content (21%) led to higher osmotic stress, resulting in reduced sugar consumption, reduced CO2 and ethanol production and a lower product volume. A darker colour and a higher sweetness factor were obtained. Reducing the sugar content (7%) had the opposite effect. Eliminating sucrose from the recipe (0%) resulted in a shortened productive fermentation time due to sugar depletion. Dough rheology was affected to a limited extent by changes in sucrose addition, although no sucrose addition or a very high sucrose level (21%) reduced the maximum dough strength. Based on the insights obtained in this study, yeast-based strategies can be developed to improve the production and quality of fermented pastry.

The influence of varying levels of molecular oxygen on the functionality of azodicarbonamide and ascorbic acid during wheat bread making.

Air, and thus also molecular oxygen (O2), is incorporated in wheat flour dough during mixing. O2 participates in several (enzymatic) reactions, including those resulting in the oxidation of free sulfhydryl groups, thereby increasing dough strength and bread volume. We here incorporated different O2 levels in dough by mixing dough samples for a fixed time under different modified atmospheres which led to significant changes in dough free sulfhydryl contents and bread volumes. Although altering the mixing time not only impacted how much O2 was incorporated in dough but also the mechanical input, the changes in dough and bread properties when using different mixing times, largely depended on differences in O2 uptake. When used in bread recipes, redox agents such as azodicarbonamide (ADA) and ascorbic acid (AH2) impact the dough sulfhydryl contents and bread volumes. The effect of different levels of O2 incorporation on dough samples which contained ADA or AH2 was studied by altering the mixing time or the O2 content in the mixing atmosphere. Lower ADA levels were needed when dough was mixed under an atmosphere enriched in O2. As AH2 requires O2 to be converted to dehydroascorbic acid (DHA) to exert its improver effect, it came as a surprise that when it was included in a dough which was prepared under O2 enriched conditions, no additional impact was obtained and that, even under reduced O2 conditions, its use still resulted in an increased bread volume. These findings suggest that AH2 oxidase very effectively uses O2 to form DHA.

Mutational analysis of wheat (Triticum aestivum L.) nucleotide pyrophosphatase/phosphodiesterase shows the role of six amino acids in the catalytic mechanism.

Nucleotide pyrophosphatases/phosphodiesterases (NPPs, PF01663) release nucleoside 5'-monophosphates from a wide range of nucleotide substrates. Only very recently, the first plant members of the NPP family were characterised (Joye et al. J Cereal Sci 51: 326-336, 2010), and little is known about their substrate-specifying residues. We elucidated the role of six amino acid residues of the recently identified and characterised Triticum aestivum L. NPP (Joye et al. J Cereal Sci 51: 326-336, 2010). Substitution of the highly conserved catalytic Thr132 into Ser or Ala completely abolished enzyme activity. Mutation of a highly conserved His255 residue into an apolar Ala suprisingly increased enzyme activity against most phosphodiester substrates. Four other residues moderately to highly conserved over NPPs of different organisms were studied as well. Mutation of the Asn153, Asn165 and Glu199 into an Arg, Ser and Asp residue, respectively, increased the relative enzyme activity against p-nitrophenyl phosphate. Furthermore, mutation of Phe194 into Ser increased the relative enzyme activity against adenosine 5'-monophosphate-containing substrates, although the overall enzyme activity of this mutant enzyme decreased. We conclude that the structural requirements and the conservation of the amino acids of the catalytic site of TaNPPr and, by extension, probably of all NPPs, are very stringent.

Redox agents and N-ethylmaleimide affect the extractability of gluten proteins during fresh pasta processing.

The gluten protein network is of great importance for pasta cooking quality. Redox agents were used as a tool to impact the protein network formation during laboratory scale fresh pasta making (mixing and sheet rolling) and cooking. SE- and RP-HPLC data showed that disulphide bonds are formed in the pre-existing gluten protein network during cooking of fresh pasta and that, in the process, glutenin polymerisation occurs faster than gliadin-glutenin copolymerisation. The thiol blocking agent N-ethylmaleimide (245ppm, expressed on semolina, dry basis) and, to a lesser extent, the oxidising agent potassium iodate (70ppm), hindered glutenin polymerisation and gliadin-glutenin copolymerisation during cooking. However, the introduction of reactive thiol groups, by addition of the reducing agent glutathione (100ppm), resulted in faster gliadin-glutenin copolymerisation during cooking.

The Role of Intact and Disintegrated Egg Yolk Low-Density Lipoproteins during Sponge Cake Making and Their Impact on Starch and Protein Mediated Structure Setting.

The main sponge cake ingredients are flour, sucrose, eggs and leavening agents. Exogenous lipids (e.g., monoacylglycerols) are often used to increase air-liquid interface stability in the batter. There is a consumer trend to avoid foods containing such additives. We here reasoned that egg yolk may be an alternative source of surface-active lipids and set out to study the role of egg yolk lipids during sponge cake making. This was done by relocating or removing them prior to batter preparation using ethanol treatments and examining how this affects cake (batter) properties and structure setting during baking. Most egg yolk lipids occur within spherical low-density lipoproteins (LDLs) which were disintegrated by the ethanol treatments. Results showed that egg yolk lipids impact air-liquid interface stability and less so cake structure setting. To prepare high-quality sponge cakes by multistage mixing preferably intact LDLs or, alternatively, their components are needed to incorporate sufficient air during mixing and to stabilize it after mixing. It was also shown that the batter contains intact LDLs in the continuous phase and disintegrated LDLs at air-liquid interfaces. Sponge cake contains intact LDLs in the cake matrix, disintegrated LDLs at air-crumb interfaces and disintegrated LDLs incorporated into the protein network.

Free wheat flour lipids decrease air-liquid interface stability in sponge cake batter.

The impact of free wheat flour lipids on air-liquid interface stability during sponge cake making was investigated. Therefore, the molecular population at the air-liquid interface in batters prepared with flour of which part of the lipids had been either relocated or removed prior to batter preparation was determined. Surface-active molecules were isolated from batter using a foam separation protocol. Diluted batter was whipped and the resulting foam was used as model system for the air-liquid interface in sponge cake batter. Relocating flour lipids prior to batter making enabled them to adsorb at the air-liquid interface in the foam. This limited the degree of protein adsorption at the air-liquid interface, but it did not impact the composition of the adsorbed protein population. Removing flour lipids prior to batter making resulted in foam containing relatively higher levels of lipids mainly originating from egg yolk. Prior removal of flour lipids impacted neither foam protein content nor foam protein composition. The resultant molecular population improved air-liquid interface stability in sponge cake batter. Thus, free wheat flour lipids and wheat flour lipids set free by solvent treatment decrease air-liquid interface stability in sponge cake batter mainly because they limit protein adsorption and, as such, interfere with the protein-dominated interface.