Improving the baking aptitude of corn starch and rice flour by using high hydrostatic pressure treatments

High hydrostatic pressure (HHP) treatments are generally used to increase food shelf-life by inactivating microorganisms and enzymes without using high temperatures. This study represents an attempt to apply HHP as a non-conventional treatment to modify the technological properties of corn starch (CS) and rice flour (RF). These two raw materials, in fact, are the most common ingredients used in gluten-free (GF) bread production, largely responsible for the final product quality decay due to starch retrogradation. Each raw material was mixed with water and then treated at 600MPa for 5min at 40\ub0C, below the gelatinization temperature of the samples at atmospheric pressure. Different pasting behaviours and solvent retention capacities of the treated (t) materials, with respect to the raw ones, were evidenced. In particular, both CSt and RFt showed a higher retention capacity in carbonate and lactic acid solvents, related to starch and protein properties, respectively. The different materials were properly combined (CS-RF; CSt-RF; CS-RFt; CSt-RFt), and each mixture was then used as the basic ingredient of a GF bread recipe. The properties of the resulting doughs were investigated both during mixing and leavening. The corresponding GF breads were evaluated for specific volume, crust and crumb color, moisture and aw. Bread crumb hardness (force at 25% of deformation) was determined, both on fresh and stored (20\ub0C, 72h; paper bags) samples: fresh breads had similar crumb hardness (0.25-0.32N), but significant differences (p<0.05) came out after 3 days of storage: CS-RF, 3.06\ub10.52N; CSt-RFt, 2.37\ub10.52N; CSt-RF, 1.58\ub10.32N; CS-RFt, 1.58\ub10.36N. Therefore, the presence of CSt and/or RFt flours decreased the staling rate of GF breads, after 72h of storage, suggesting that the HHP treatment may be successfully used to improve GF bread shelf-life

Can high hydrostatic pressures modify the technological properties of gluten-free raw materials?

Gluten-free (GF) baked goods contain a large amount of starch whose behavior during processing and storage greatly influences their quality and shelf-life. Even if high hydrostatic pressures (HHP) are generally used to inactivate microorganisms and enzymes, they were here employed as a non-conventional treatment to modify the technological aptitude of corn starch (CS), rice flour (RF) and waxy rice flour (WRF), raw materials commonly used in GF products. The samples were pre-conditioned up to 40% moisture content and then treated with HHP. The following parameters were considered: pressure (400MPa; 600MPa), pressure holding time (5min; 10min) and temperature (20\ub0C; 40\ub0C). The untreated and treated samples were evaluated for their viscoamylographic features, solvent retention capacity (SRC), thermal properties, X-ray diffractive and ultrastructural characteristics. According to the pressure applied, different pasting behaviours and SRC were evidenced. RF-starch was partially de-structurated at both the pressures applied, as highlighted by the lower peak values obtained (650 and 620BU, respectively) in comparison to that of the untreated sample (756BU). Few differences were found for WRF, indicating a lower susceptibility to pressure. CS treated at 600MPa presented diminished pasting properties in comparison to the untreated CS and to CS treated at 400MPa: even if the gelatinization temperature of all these samples was around 70\ub0C, a clear shift of the 600MPa treated CS viscoamylographic curve was evidenced. Furthermore, both CS and RF treated at 600MPa showed a higher retention capacity of carbonate and lactic acid solvents, respectively related to starch and protein properties. HHP treatments thus seem to be able to change the technological behaviour of RF and CS, and this potential positive effect has been actually evidenced in preliminary breadmaking trials

Effect of high pressure processing on the baking aptitude of corn starch and rice flour

The effectiveness of high pressure treated ingredients in slowing down the staling kinetic of gluten-free breads, in comparison with their untreated counterparts, was investigated. In terms of high pressure processing, both corn starch (CS) and rice flour (RF) were treated (CSt; RFt) at 600 MPa for 5 min at 40 C; a very high sample-to-water concentration level was used. Four different bread recipes were then tested, starting from the following mixtures: CS \ufe RF for the control sample, CSt \ufe RFt, CSt \ufe RF and CS \ufe RFt. The properties of the doughs during mixing and leavening were investigated, as well as the GF breads characteristics during storage. In regard to crumb softness, similar results were evidenced among the four recipes just after baking, while during 3 days of storage at controlled conditions, the presence of high pressure treated corn starch or rice flour was effective in slowing down the staling rate of bread crumb. High pressure treatment applied to raw materials could therefore be successfully used to improve gluten-free bread shelf-life, and these results could assist in advancing the quality of gluten-free bread for the celiac consumer

Pressure and temperature combination for inactivation of soymilk trypsin inhibitors

High hydrostatic pressure (HHP) processing, an emerging technology for food preservation, in combination with thermal treatment (250/50, 550/19, 550/65, and 550/80 MPa/�C) was applied to soymilk made from previously soaked soybeans (in distilled water or 0.5% sodium bicarbonate solution). First order kinetics constants ranging from 0.081 to 0.217 min-1, for residual trypsin, were estimated in soymilk from soaked soybeans at selected pressure-temperature combinations. Residual trypsin, at 550 MPa and 80 �C, was high at higher HHP holding times. The highest percentage of residual trypsin (76%) was estimated after a 15 min holding time. The use of sodium bicarbonate for soaking of soybeans synergistically decreased the trypsin inhibitor activity in soymilk in comparison with residual trypsin using distilled water alone. � 2009 Elsevier Ltd. All rights reserved

Optimization of spray-drying process conditions for the production of maximally viable microencapsulated L. acidophilus NCIMB 701748

Inrecent years, the use of spray drying for the production of anhydrobiotics has gained the interest of functional food manufacturers, mainly due to cost efficiencies and enhanced product and process flexibility (e.g., enhanced shelf life). In the present work, spray-drying conditions (air inlet temperature and feed flow rate) were optimized for the microencapsulation of the thermo sensitive probiotic lactobacilli strains Lactobacillus acidophilus stabilized in a 60:20:20 (w/w) maltodextrin: whey protein concentrate: D-glucose carrier. A 23 full-factorial experimental design was constructed with air inlet temperature (120, 140, and 160°C) and feed flow rate (6, 7.5, and 9.0 mL/min) as the independent variables and total viable counts (TVC), water activity (a w ), and cyclone recovery (CR) defined as the dependent variables. The increase in air inlet temperature from 120 to 160°C induced a significant (p < 0.001) reduction in the TVC from 9.02 to 7.20 log cfu/g, which corresponds to a97.5% loss of the L. acidophilus viable counts. On the other hand, the increase in the feed flow rate from 6 to 7.5 mL/min significantly reduced (p < 0.001) the heat-induced viability loss. A further increase in the feeding rate did not further modify the achieved thermo protection, and a detrimental impact of cyclone recovery (reduction) and water activity (increase) of the powder was observed. Using pruned quadratic mathematical models, the optimum spray-drying conditions for the production of maximally viable microencapsulated L. acidophilus were 133.34°C and 7.14 mL/min. The physicochemical and structural characteristics of the powders produced were acceptable for application with regards to residual water content, particles mean size, and thermo physical properties to ensure appropriate storage stability under room temperature conditions, with a low inactivation rate of L. acidophilus. Microcapsules appeared partially collapsed by scanning electron microscope with a spherical shape with surface concavities