Elke K. Arendt

Crust and crumb characteristics of gluten free breads

Gluten free breads often have poor crust and crumb characteristics and the current study was conducted to help alleviate this problem. A commercial wheat starch (Codex Alimentarius) gluten free flour was supplemented with seven dairy powders (0%, 3%, 6%, 9% inclusion rates based on flour weight). Initially a fixed water level was used (trial 1) and the resulting batters were proofed and baked. The breads were tested 24 h after baking. Powder addition reduced loaf volume by circa 6% (P < 0.001). Increasing the inclusion levels of the powders decreased loaf volume (P < 0.001) with a decrease of 8% for the highest level. Powder addition generally decreased the crumb L*/b* (white/yellow) ratio. Crust L* values were significantly reduced. All of the powders increased crumb hardness (P < 0.001) with the exception of demineralised whey powder. Ten and 20% additional water (trial 2) was added to the formulation and the resulting breads had higher volume, and a much softer crust and crumb texture. Sensory analysis revealed a preference for breads containing skim milk replacer, sodium caseinate and milk protein isolate.

Sourdough Bread Made from Wheat and Nontoxic Flours and Started with Selected Lactobacilli Is Tolerated in Celiac Sprue Patients

ABSTRACT This work was aimed at producing a sourdough bread that is tolerated by celiac sprue (CS) patients. Selected sourdough lactobacilli had specialized peptidases capable of hydrolyzing Pro-rich peptides, including the 33-mer peptide, the most potent inducer of gut-derived human T-cell lines in CS patients. This epitope, the most important in CS, was hydrolyzed completely after treatment with cells and their cytoplasmic extracts (CE). A sourdough made from a mixture of wheat (30%) and nontoxic oat, millet, and buckwheat flours was started with lactobacilli. After 24 h of fermentation, wheat gliadins and low-molecular-mass, alcohol-soluble polypeptides were hydrolyzed almost totally. Proteins were extracted from sourdough and used to produce a peptic-tryptic digest for in vitro agglutination tests on K 562(S) subclone cells of human origin. The minimal agglutinating activity was ca. 250 times higher than that of doughs chemically acidified or started with bakers yeast. Two types of bread, containing ca. 2 g of gluten, were produced with bakers yeast or lactobacilli and CE and used for an in vivo double-blind acute challenge of CS patients. Thirteen of the 17 patients showed a marked alteration of intestinal permeability after ingestion of bakers yeast bread. When fed the sourdough bread, the same 13 patients had values for excreted rhamnose and lactulose that did not differ significantly from the baseline values. The other 4 of the 17 CS patients did not respond to gluten after ingesting the bakers yeast or sourdough bread. These results showed that a bread biotechnology that uses selected lactobacilli, nontoxic flours, and a long fermentation time is a novel tool for decreasing the level of gluten intolerance in humans.

Characterization of proteolysis during the ripening of semi-dry fermented sausages

The respective contribution of indigenous enzymes and enzymes from starter bacteria to proteolysis in fermented sausages were determined by comparing the proteolytic changes occurring in sausages resulting from the presence of a proteolytic strain of Staphylococcus carnosus, i.e. S. carnosus MC 1 to the proteolytic changes occurring in control sausages containing glucono-δ-lactone (GDL) and an antibiotic mixture. Proteolysis was quantified by assaying for non-protein nitrogen (NPN) and free amino acids. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and reversed phase high performance liquid chromatography (RP-HPLC) were used to qualitatively assess the proteolytic changes in the sarcoplasmic and myofibrillar proteins as ripening progressed. The concentration of NPN and free amino acids increased in both sausages initially, but subsequently decreased towards the end of ripening in sausages inoculated with the starter culture. SDS-PAGE showed a similar pattern of proteolysis of sarcoplasmic proteins in both sausages, while of the two sausage types; the S. carnosus MC 1 inoculated sausages exhibited the most intense degradation of myofibrillar proteins, especially myosin and actin. RP-HPLC profiles of 2% trichloroacetic acid (TCA)-soluble peptides for the two sausage types were similar, with the production of numerous hydrophilic peptides. N-Terminal amino acid sequence analysis and sequence homology with proteins of known primary structure showed that six of the TCA-soluble peptides were released from the sarcoplasmic (myoglobin and creatine kinase) and myofibrillar (troponin-I, troponin-T and myosin light chain-2) proteins. In addition, the initial degradation of sarcoplasmic proteins was due to the activity of indigenous proteinases, while both indigenous and bacterial enzymes contributed to the initial degradation of myofibrillar proteins. Furthermore, indigenous enzymes were responsible for the release of TCA-soluble peptides, which, were further hydrolysed by bacterial enzymes.

Development of bioactive food packaging materials using immobilised bacteriocins lacticin 3147 and nisaplin.

Immobilisation of the bacteriocins nisin and lacticin 3147 to packaging materials was investigated. Stability of both cellulose-based bioactive inserts and anti-microbial polyethylene/polyamide pouches was examined over time. Anti-microbial activity against the indicator strain Lactococcus lactis subsp. lactis HP, in addition to Listeria innocua DPC 1770 and Staphylococcus aureus MMPR3 was observed for all bacteriocin-adsorbed materials. Activity retention of the inserts showed an initial decrease in the first week of storage but remained stable for the remaining 3 months of the trial. However, adsorption of lacticin 3147 to plastic film was unsuccessful, nisin bound well and the resulting film maintained its activity for 3-month period, both at room temperature and under refrigeration. When applied to food systems, the anti-microbial packaging reduced the population of lactic acid bacteria in sliced cheese and ham stored in modified atmosphere packaging (MAP) at refrigeration temperatures, thus extending the shelf life. Nisin-adsorbed bioactive inserts reduced levels of Listeria innocua by > or = 2 log units in both products, and Staphylococcus aureus by approximately 1.5 log units in cheese, and approximately 2.8 log units in ham. Similar reductions were observed in cheese vacuum-packaged in nisin-adsorbed pouches.

Network Formation in Gluten-Free Bread with Application of Transglutaminase

ABSTRACT One of the main problems associated with gluten-free bread is obtaining a good structure. Transglutaminase (TGase), an enzyme that catalyzes acyl-transfer reactions through which proteins can be cross-linked could be a way to improve the structure of gluten-free breads. The objective of this study was to evaluate the impact of TGase at different levels (0, 0.1, 1, and 10 U of TGase/g of protein) on the quality of gluten-free bread. The recipe consisted of white rice flour (relative amount: 35), potato starch (30), corn flour (22.5), xanthan gum (1), and various protein sources (skim milk powder [SMP] [12.5], soya flour, and egg powder). The influence of the various proteins in combination with the different addition levels of TGase on bread quality (% bake loss, specific volume, color, texture, image characteristics, and total moisture) was determined. Confocal laser-scanning microscopy (CLSM) was used to evaluate the influence of TGase on the microstructure of the bread. Baking tests showed that...

Gluten-Free Bread from Sorghum: Quality Differences Among Hybrids

ABSTRACT Gluten-free breadmaking quality of 10 sorghum flours was compared using (relative basis) decorticated sorghum flour (70), corn starch (30), water (105), salt (1.75), sugar (1), and dried yeast (2). Batter consistency was standardized by varying water levels to achieve the same force during extrusion. Crumb properties were evaluated by digital image analysis and texture profile analysis (TPA). Significant differences (P < 0.001) in crumb grain were found among the hybrids with mean cell area ranging from 1.3 to 3.3 mm2 and total number of cells ranging from 13.5 to 27.8/cm2. TPA hardness values of the crumb also varied significantly (P < 0.001). Based on significant correlations (P < 0.01), starch damage, influenced by kernel hardness, was identified as a key element for these differences. Breads differed little in volume, height, bake loss, and water activity. Investigation of added ingredients on bread quality was conducted using response surface methodology (RSM) with two sorghum hybrids of opp...

Nutritive value and chemical composition of pseudocereals as gluten-free ingredients

The only treatment available for patients with coeliac disease is a lifelong elimination of food products containing gluten. The gluten-free products currently available in the market are considered of low quality and poor nutritional value. In the present study, the pseudocereals amaranth, quinoa and buckwheat were studied as potential healthy ingredients for improving the nutritional quality of gluten-free breads. The pseudocereal seeds and pseudocereal-containing gluten-free breads were evaluated in terms of their protein, fat, total starch, dietary fibre, ash and mineral content as well as their fatty acid composition. The pseudocereal containing gluten-free breads showed significantly higher levels of protein, fat, fibre and minerals than the control bread. The attributes of these breads conform to the experts nutritional recommendations for the gluten-free diet and gluten-free foods. These results suggest that the pseudocereals amaranth, quinoa and buckwheat can represent a healthy alternative to frequently used ingredients in gluten-free products.

Textural Comparisons of Gluten-Free and Wheat-Based Doughs, Batters, and Breads

ABSTRACT Studies were conducted with two newly developed gluten-free bread recipes. One was based on corn starch (relative amount 54), brown rice (25), soya (12.5), and buckwheat flour (8.5), while the other contained brown rice flour (50), skim milk powder (37.5), whole egg (30), potato (25), and corn starch (12.5), and soya flour (12.5). The hydrocolloids used were xanthan gum (1.25) and xanthan (0.9) plus konjac gum (1.5), respectively. Wheat bread and gluten-free bread made from commercial flour mix were included for comparison. Baking tests showed that wheat and the bread made from the commercial flour mix yielded significantly higher loaf volumes (P < 0.01). All the gluten-free breads were brittle after two days of storage, detectable by the occurrence of fracture, and the decrease in springiness (P < 0.01), cohesiveness (P < 0.01), and resilience (P < 0.01) derived from texture profile analysis. However, these changes were generally less pronounced for the dairy-based gluten-free bread, indicating ...

Sourdough in gluten-free bread-making: an ancient technology to solve a novel issue?

The increasing demand for high quality gluten-free (GF) bread, clean labels and natural products is raising the need for new approaches in GF bread-making. Sourdough is the foremost fermentation used for baking purposes and it has been proven to be ideal for improving the texture, palatability, aroma, shelf life and nutritional value of wheat and rye breads. These characteristic features derive from the complex metabolic activities of the sourdough-resident lactic acid bacteria and yeasts, e.g. acidification, production of exopolysaccharides, proteolytic- amylolytic- and phytase activity, and production of antimicrobial substances. These effects have been extensively studied and well described for traditional baking, whereas little is known about the role of sourdough in GF baking. Yet, the microbiological and qualitative characterisation of local GF fermented products indicate an overlap with the microbiota of wheat/rye fermentation and suggest that the positive metabolic activities of the sourdough microbiota are still retained during fermentation of GF crops. Thus, the use of sourdough in GF baking may be the new frontier for improving the quality, safety and acceptability of GF bread.

Application of Response Surface Methodology in the Development of Gluten-Free Bread

ABSTRACT The formulation of gluten-free (GF) bread of high quality presents a formidable challenge as it is the gluten fraction of flour that is responsible for an extensible dough with good gas-holding properties and baked bread with good crumb structure. As the use of wheat starch in GF formulations remains a controversial issue, naturally GF ingredients were utilized in this study. Response surface methodology was used to optimize a GF bread formulation primarily based on rice flour, potato starch, and skim milk powder. Hydroxypropylmethylcellulose (HPMC) and water were the predictor variables. Analyses of the treatments from the design were made 24 hr after baking. Specific volume and loaf height increased as water addition increased (P 4 mm2) decreased with increasing levels of HPMC and water. Optimal ing...