Manuela Mariotti

Influence of Psyllium, sugar beet fibre and water on gluten-free dough properties and bread quality

Celiac patients generally have a low intake of protein and fibre attributed to their gluten-free (GF) diet. To satisfy the increasing demand for healthier products, this research focused on the effects of the supplementation of Psyllium (P) and sugar beet fibre (SB) on the mixing and leavening behaviour of gluten-free doughs. Four doughs, having different consistencies that made them suitable to be poured into moulds or to be shaped, and their corresponding breads were evaluated. The results obtained suggested that a lower consistency is preferred to assure good dough performances during leavening, in particular when ingredients having a high water affinity are included into the recipe. Both P and SB improved the workability of the doughs, but P played a central role on GF bread development, thanks to its film forming ability, and evidenced a more effective antistaling effect, thanks to its high water binding capacity.

Macromolecular interactions and rheological properties of buckwheat-based dough obtained from differently processed grains.

The physicochemical properties of the protein and starch fractions of flour obtained from buckwheat grains that were previously dehulled or puffed after dehulling were investigated. Dehulling removed most of the nonprotein, nonstarch components of the grain, without affecting the chemical and structural features of the protein and starch components, as made evident by microstructural and spectroscopic measurements. Puffing resulted in extensive modifications of the interprotein network as well as in most of the properties of the buckwheat starch. Flours obtained from dehulled or puffed after dehulling grains were blended with 60-80% wheat flour and tested for their dough-making ability. Blends containing dehulled and puffed buckwheat flours gave dough of much lower quality than dehulled, but had water-holding properties that may be of interest for the shelf life of baked products.

Physical and structural changes induced by high pressure on corn starch, rice flour and waxy rice flour

The impact of high pressure (HP) processing on corn starch, rice flour and waxy rice flour was investigated as a function of pressure level (400MPa; 600MPa), pressure holding time (5min; 10min), and temperature (20°C; 40°C). Samples were pre-conditioned (final moisture level: 40g/100g) before HP treatments. Both the HP treated and the untreated raw materials were evaluated for pasting properties and solvent retention capacity, and investigated by differential scanning calorimetry, X-ray diffractometry and environmental scanning electron microscopy. Different pasting behaviors and solvent retention capacities were evidenced according to the applied pressure. Corn starch presented a slower gelatinization trend when treated at 600MPa. Corn starch and rice flour treated at 600MPa showed a higher retention capacity of carbonate and lactic acid solvents, respectively. Differential scanning calorimetry and environmental scanning electron microscopy investigations highlighted that HP affected the starch structure of rice flour and corn starch. Few variations were evidenced in waxy rice flour. These results can assist in advancing the HP processing knowledge, as the possibility to successfully process raw samples in a very high sample-to-water concentration level was evidenced. INDUSTRIAL RELEVANCE This work investigates the effect of high pressure as a potential technique to modify the processing characteristics of starchy materials without using high temperature. In this case the starches were processed in the powder form - and not as a slurry as in previously reported studies - showing the flexibility of the HP treatment. The relevance for industrial application is the possibility to change the structure of flour starches, and thus modifying the processability of the mentioned products.

Development of a Type I gluten‐free sourdough

The aim of this study was the setting up of a gluten‐free sourdough from selected lactobacilli and yeasts isolated from a traditional wheat‐based Type I sourdough. A gluten‐free matrix was inoculated with Lactobacillus sanfranciscensis and Candida humilis, fermented to pH 4·0, and constantly propagated for ten times. A stable association between micro‐organisms was observed from the second refreshment with mean values of 9·08 ± 0·25 log CFU g−1 for lactobacilli and 7·81 ± 0·07 log CFU g−1 for yeasts. In order to have a good workability of the dough, a 230 BU consistency was considered. Rheofermentographic indices remained constant over the ten refreshments, showing an average value of 23·2 mm dough height in about 7·5 h. The CO2 production and retention volumes reached average values of 1430 and 1238 ml respectively. The microbiological and technological data obtained highlighted that a GF sourdough was effectively developed.

Tuning Physical Properties of Tomato Puree by Fortification with Grape Skin Antioxidant Dietary Fiber

Grape skins recovered from winemaking by-products were investigated for use as sustainable, antioxidant fiber-rich ingredient for the innovation of low-energy dense tomato puree. Six tomato purees fortified with grape skin antioxidant fiber, with varying particle size distribution, and two control tomato purees were studied. Physical parameters of purees were analyzed upon mixing and either an intensive heat treatment or an optimized heat treatment designed to achieve six decimal reductions of a target microorganism (Alicyclobacillus acidoterrestris) as recommended for pasteurization of acidic fruit products. Mixing of grape skin antioxidant fiber with tomato purees led to a decrease in both surface-weighted mean diameter (Sauter mean diameter, d(3,2)) and volume-weighted mean diameter (d(4,3)) values and an increase in span. Changes in these descriptors were most significant in purees added with the smallest particle sizes. Thermal stabilization of purees slightly decreased the d(3,2) values further and increased d(4,3) values, suggesting concomitant occurrence of particle disaggregation and formation of flocs within the food matrix. Phenolic solubility was inversely correlated to d(3,2) values. Bostwick consistency, storage (G′) and loss (G″) moduli, and complex viscosity (η*) increased in the fortified purees. The η* values displayed a positive correlation with d(4,3) values. Variations in Hunter colorimetric parameters were within the acceptability threshold. Overall, the information obtained provides knowledge to assist development of fiber-rich, low-energy dense fruit purees.

Technology of Baked Goods

The chapter describes the main ingredients (wheat flour, water, salt, sugar, and fats) and the different steps of the chain used for making baked goods, from milling to the baking process (mixing, leavening, proofing, dough makeup and baking operations). An overview of the main analytical methods used to determine the quality of baked goods (e.g. fundamental rheology, descriptive empirical measurements, and innovative approaches) is also included.

Gluten-Free Bread : Influence of Sourdough and Compressed Yeast on Proofing and Baking Properties

The use of sourdough is the oldest biotechnological process to leaven baked goods, and it represents a suitable technology to improve traditional bread texture, aroma, and shelf life. A limited number of studies concerning the use of sourdough in gluten-free (GF) breadmaking have been published in comparison to those on traditional bread. The aim of this study was to compare the properties of GF breads obtained by using a previously in-lab developed GF-sourdough (SD), compressed yeast (CY; Saccharomyces cerevisiae) or their mixture (SDCY) as leavening agents; more specifically, it aims to confirm the findings of a previous studies and to further improve (both in terms of recipe and process) the features of the resulting GF breads. Dough pH and rheological properties were measured. Fresh and stored breads were characterized for weight, height, specific volume, crust and crumb color, moisture, water activity, crumb hardness, and porosity. The combination SDCY was effective in improving bread volume and softness when compared to SD only. Furthermore, SD- and SDCY-crumbs exhibited a less crumbly behavior during storage (69 h, 25 °C, 60% of relative humidity) in comparison to CY-breads. This study confirms the positive effect of SD in GF breadmaking, in particular when used in combination with CY.