Bread from composite cassava-wheat flour: I. Effect of baking time and temperature on some physical properties of bread loaf

The use of composite cassava-wheat (CCW) flour for commercial breadmaking purposes and consumption of CCW bread are relatively new in Nigeria. This study investigated the effect of baking temperature and time on some physical properties of bread from composite flour made by mixing cassava and wheat flour at ratio of 10:90 (w/w). A central composite rotatable experimental design was used while the baking temperature and time investigated ranged from 190 to 240 °C and 20 to 40 min, respectively. Loaf volume, weight and specific volume varied significantly (p < 0.001) from 440 to 920 cm³, 162 to 183 g and 3.31 to 5.32 cm³/g, respectively. The tristimulus color parameters such as L¹ (lightness) and brownness index (BI) of the crust varied significantly (p < 0.01) from 31 to 72 and 68 to 123, respectively. Moreover, Fresh crumb moisture, density, porosity and softness as well as the dried crumb hardness were also significantly (p < 0.01) affected by both the baking temperature and time with values ranging from 34% to 39%, 0.16 to 0.20 g/cm³, 0.69 to 0.80, 13.00 to 18.05 mm and 0.90 to 2.05 kgf, respectively. Due to the complex effect of temperature and time combination, most of the measured properties could not be reliably predicted from the second order response surface regression equations except the loaf weight and crumb moisture. Further studies are required to optimize the CCW bread baking process based on some storage and consumption qualities.     

Migration of α-tocopherol from LDPE films to corn oil and its effect on the oxidative stability

The migration of α-tocopherol (α-T) from low density polyethylene (LDPE) films, added with 20 (film A) and 40 mg g^?1 (film B) to corn oil for 12 weeks at 5, 20 and 30 °C was determined. A LDPE film added with no α-T was used as control (film C). Diffusion coefficient (D) values for the film A system were 1.4 × 10^?11, 7.1 × 10^?11 and 30.3 × 10^?11 cm² s^?1 at 5, 20 and 30 °C, respectively. Meanwhile, D values for the film B system were 1.3 × 10^?11, 9.6 × 10^?11 and 51.1 × 10^?11 cm² s^?1 at the same temperatures. The activation energy (E_a) for the diffusion of α-T was 126.5 (film A) and 105.9 kJ mol^?1 (film B). The effect of the migration of α-T on the oxidative stability of corn oil was evaluated by monitoring hexanal content by solid phase micro-extraction (SPME) and gas chromatography. The hexanal content in the oil showed that both films added with α-T resulted suitable to maintain the oxidative stability of the oil for about 16 weeks at 30 °C, compared to 12 weeks for the oil in contact with the film C.     

Effect of Honey as Partial Sugar Substitute on Pasting Properties,Consumer Preference and Shelf Stability of Cassava-Wheat Composite Bread

The effect of partial substitution of sugar with liquid honey on the pasting properties of cooked dough made from cassava-wheat composite (10:90) flour as well as the sensory preference and shelf stability of its bread was investigated. Sucrose (S) in the bread recipe formulation was substituted with honey (H) at levels 0, 10, 20, 30, 40 and 50%, respectively to give 6 treatments, namely 0H:100S, 10H:90S, 20H:80S, 30H:70S, 40H:60S and 50H:50S. Amylograph pasting properties of the dried crumbs were determined using standard analytical procedures. Fresh bread samples were subjected to sensory evaluation and fungal count during storage (6 days). Peak, final and setback viscosities of bread crumb decreased (32.29 to 25.33, 58.54 to 43.00 and 30.96 to 23.66 RVU), respectively as the level of honey inclusion increased. Honey substitution levels used did not significantly (p > 0.05) affect aroma and texture of the bread samples but composite bread with 20% level of honey substitution was most preferred in terms of colour while composite bread with 30% level of honey substitution was most acceptable in terms of taste and overall acceptability. Fungal count in stored honey-cassava-wheat bread varied significantly (p < 0.05) from 0.6 to 4.0 × 10², 1.0 to 6.9 × 10², 2.2 to 57.0 × 10², 32.0 to 135.7 × 10², 34.0 to 140.0 × 10² and 42.0 to 159.3 × 10²) cfu/ml from day 1 to day 6, respectively. From the study, it was concluded that substitution of sugar with honey in dough formulations significantly (p < 0.05) affects dough pasting properties, improves acceptability of the composite bread and reduces staling rate.     

Influence of relative humidity on carbon dioxide sorption in wheat gluten films

The influence of relative humidity (RH) on carbon dioxide sorption at 10⁵ Pa in wheat gluten films (WGF) was investigated in the range of 0–96% RH at 25 °C. The amount of water sorbed by these protein based films reached up to 60% of the dry weight at 96% RH. Carbon dioxide sorption increased with water content, ranging from 2.8 × 10⁻⁴ to 1.9 × 10⁻² mol Pa⁻¹ m⁻³ respectively at 0% and 96% RH. This behavior was tentatively explained on the grounds that sorbed water enhanced carbon dioxide accessibility to protein active sorption sites. The dependence of both the solubility and the diffusivity coefficients of CO₂ and O₂ on WGF water content explains the very good permselectivity of these films observed at high RH values (22 at 93% RH and 25 °C).     

Influence of yeast and vegetable shortening on physical and textural parameters of frozen part baked French bread

The objective of this project was to study the influence of yeast and vegetable shortening on physical and textural parameters of frozen part baked French bread stored for 28 days and to produce a frozen part baked bread with physical and textural characteristics similar to those of the fresh one. Four formulations were used with different quantities of yeast and vegetable shortening. Dough was prepared by mixing all ingredients in a dough mixer at two speeds. After resting, the dough was divided into 60 g pieces, molded and proofed. The bread was partially baked for 7 min at 250°C, in a turbo oven. After cooling, it was frozen until the core temperature reached −18°C and stored at the same temperature up to 28 days. Once a week, samples were removed from the freezer to complete the baking process, without previous thawing. Mass, volume, water content, firmness, cohesiveness and springiness were measured 1 h after final baking. Resistance to extension and extensibility of dough were measured after mixing. Specific volume and chewiness were determined. Bread with higher yeast content presented a higher specific volume, whereas vegetable shortening reduced its crumb firmness and chewiness.     

The protective effect of monosodium glutamate on survival of Lactobacillus rhamnosus GG and Lactobacillus rhamnosus E-97800 (E800) strains during spray-drying and storage in trehalose-containing powders

The use of trehalose as a means of preserving Lactobacillus rhamnosus GG (LGG) and L. rhamnosus E-97800 (E800) during spray-drying and the effects of incorporated monosodium glutamate (MSG) in the carrier medium on the survival rates during drying and storage were examined. E800 was more resistant to heat than LGG in 20%, w/w, trehalose; the d-values at 65 °C were 14 s and 5.1 s, respectively. An air outlet temperature of 65–70 °C was taken as optimal for the drying process, as the resultant moisture levels in trehalose containing these bacteria were 4.1% (w/w) and 3.79% (w/w) with corresponding viable counts of 3.65 × 10⁸ cfu mL^?1 and 1.80 × 10⁹ cfu mL^?1, respectively. The presence of MSG increased the final viable counts of LGG and E800 to 3.05 × 10⁹ cfu mL^?1 and 1.30 × 10⁹ cfu mL^?1, respectively. Survival of LGG and E800 remained constant at a minimum level of ～10⁸ cfu mL^?1 during storage at 25 °C in trehalose–MSG medium.     

Estimation of the diffusivities of sodium chloride,potassium sorbate and sodium bisulphite in mango slices processed by hurdle technology

The fractional amount of sodium chloride, potassium sorbate and sodium bisulphite were evaluated in mango slices immersed in limited volumes of syrup at 25, 50 and 70 °C. The syrup contained 250 g sucrose, 1.5 g sodium chloride, 0.5 g potassium sorbate and 0.25 g sodium bisulphate per kilogram of solution. The sodium chloride concentration in the syrup was confirmed with a flame photometer, and the concentrations of potassium sorbate and sodium bisulphite were determined using high-performance liquid chromatography (HPLC). Fick’s second law was used to calculate effective diffusion coefficients and to predict solute content in the mango slices. Diffusion coefficients were affected by temperature and were correlated by the Arrhenius equation. The experimental data fit the proposed mathematical model well, allowing prediction of the system’s behavior at different temperatures. The resultant diffusivities ranges were 2.63–3.54 × 10^?9 m²/s for sodium chloride, 3.88 × 10^?9–8.3 × 10^?10 m²/s for potassium sorbate and 1.83 × 10^?7–5.98 × 10^-8 m²/s for sodium bisulphite.     

Aluminium contents in baked meats wrapped in aluminium foil

In this investigation, the effect of cooking treatments (60 min at 150 °C, 40 min at 200 °C, and 20 min at 250 °C) on aluminium contents of meats (beef, water buffalo, mutton, chicken and turkey) baked in aluminium foil were evaluated. Cooking increased the aluminium concentration of both the white and red meats. The increase was 89–378% in red meats and 76–215% in poultry. The least increase (76–115%) was observed in the samples baked for 60 min at 150 °C, while the highest increase (153–378%) was in samples baked for 20 min at 250 °C. It was determined that the fat content of meat in addition to the cooking process affected the migration of aluminium (r² = 0.83; P < 0.01). It was also found that raw chicken and turkey breast meat contained higher amounts of aluminium than the raw chicken and turkey leg meat, respectively. Regarding the suggested provisional tolerable daily intake of 1 mg Al/kg body weight per day of the FAO/WHO Expert Committee on Food Additives, there are no evident risks to the health of the consumer from using aluminium foil to cook meats. However, eating meals prepared in aluminium foil may carry a risk to the health by adding to other aluminium sources.     

Time–temperature study of the kinetics of migration of DPBD from plastics into chocolate,chocolate spread and margarine

Migration of low molecular weight substances into foodstuffs is a subject of increasing interest and an important aspect of food packaging because of the possible hazardous effects on human health.The migration of a model substance (diphenylbutadiene) from low-density polyethylene (LDPE) was studied in foodstuffs with high fat contents: chocolate, chocolate spread and margarines (containing 61% and 80% fat).A simplifying mathematical model based on Fick’s diffusion equation for mass transport processes from plastics was used to derive effective diffusion coefficients which take also kinetic effects in the foods into account and to determine partition coefficients between plastic and food. With this model migration levels obtainable under other storage conditions can be predicted. The effective diffusion coefficients for both margarines stored at 5 °C (3.0–4.2 × 10⁻¹⁰ cm² s⁻¹) and at 25 °C (3.7–5.1 × 10⁻⁹ cm²  s⁻¹) were similar to each other, lower than for chocolate spread stored at 5 °C (9.1 × 10⁻¹⁰ cm² s⁻¹) and higher than the diffusion coefficient for chocolate stored at 25 °C (2.9 × 10⁻¹⁰ cm² s⁻¹). Good agreement was found between the experimental and the estimated data, allowing validation of this model for predicting diffusion processes in foodstuffs with high fat contents.     

Impact of the Baking Duration on Bread Staling Kinetics

This paper presents a study on the impact of the duration of the baking plateau on staling kinetics in the case of bread crumb made of sourdough; it follows Le-Bail et al. Journal of Cereal Science 50:235–240, (2009)a previous study proposed by Le-Bail et al. Journal of Cereal Science 50:235–240, (2009) on the impact of heating rate during baking on staling parameters. Degassed bread dough was baked in a miniaturized baking system with baking plateau of 0, 4, and 8 min at 98 °C corresponding to a total baking time of 10, 14 and 18 min respectively (simulating from underbaked to fully baked bread). Results showed that longer baking time resulted in the higher Young’s modulus of the baked dough at the end of staling was. It was observed as in Le-Bail et al. Journal of Cereal Science 50:235–240, (2009) that the crystallization of amylopectin occurred a few days before the hardening of the baked crumb during staling. The amount of freezable water decreased during staling (over 10 days period), which was in agreement with the increase in amylopectin crystallites during staling which trap water. The amount of soluble amylose increased with increasing duration of the baking plateau at 98 °C, indicating that for prolonged baking, an increasing amount of amylose is leached outside of the starch granules. This was proposed as an explanation for the higher Young’s modulus of the crumb at the end of staling.     

A risk characterization model of Salmonella Typhimurium in Irish fresh pork sausages

A second-order simulation model was built to estimate the risk of Salmonella Typhimurium associated with the consumption of Irish fresh pork sausages. To select appropriate hazard characterization models, an initial appraisal of the current dose-response models was conducted. The cooking modality of grilling was associated with a higher mean risk of infection per serving (1.399 × 10^? 6; 95% CI: 7.54 × 10^? 7–2.65 × 10^? 6) than frying (6.246 × 10^? 7, 95% CI: 2.78 × 10^? 7–1.17 × 10^? 6). When the risk was extrapolated over the consumption in a year period, the mean risk of infection increased considerably to 8.541 × 10^? 5 with an expected number of infections and illnesses of 184.3 (95% CI: 26–664) and 17 (95% CI: 2–63), respectively. Results highlighted the importance of consumer education, as scenario analysis predicted that, for the current level of Salmonella in pork sausage, decreasing the product's cold storage by approximately 8 h and cooking for an additional half minute can reduce the current risk level by ～ 50%.     

Enzymatic synthesis of banana flavour (isoamyl acetate) by Bacillus licheniformis S-86 esterase

New carboxylesterase from organic-solvent-tolerant Bacillus licheniformis S-86 strain was characterized. The enzyme named as type II esterase showed an optimal activity in the temperature range 60–65 °C and pH 8.0. The enzyme was moderatly thermostable (half-life of 1 h at 50 °C), but remarkable stable at extremely alkaline pH, retaining 100% of its activity at pH 10.0–11.0. Furthermore, the esterase showed high stability in detergents (86% residual activity in 10% SDS), and also 0.1% ionic and non-ionic detergents are inducers of enzyme activity. PMSF, a serine protease inhibitor, did not show any effect on the activity. The immobilized type II esterase was able to synthesize isoamyl acetate from isoamyl alcohol and p-nitrophenyl acetate (acyl donor) in n-hexane. The resulting ester yield (42.8%), obtained at a low temperature (28 °C) and with a very low amount of enzyme (4.6 × 10^?5 mg ml^?1), indicates a high potential for type II esterase in isoamyl acetate synthesis for production purposes.     

Effect of Lactobacillus brevis-based bioingredient and bran on microbiological,physico-chemical and textural quality of yeast-leavened bread during storage

The effects of wheat bran and of a Lactobacillus brevis-based bioingredient (LbBio), obtained after growth in flour-based medium, on quality of yeast-leavened wheat bread (WWB) were investigated. Bran was used in bread formulation by substituting a part (20 g/100 g) of white wheat flour (WBB), while LbBio was used instead of the water content (WWB + LbBio and WBB + LbBio). The use of LbBio in WWB resulted in the biological acidification of the dough due to lactic, phenyllactic and OH-phenyllactic acid contents determining a high fermentation quotient value and an improved bread texture and microbiological quality. Conversely, wheat bran reduced the specific volume and crumb hardness during storage at 25 °C, and affected the antibacterial ability of LbBio during 30 °C storage. Our findings demonstrated that LbBio counteracted the negative effects of bran and allowed to obtain an enriched fibre bread with specific volume and soft crumb comparable to bread without bran.Industrial relevanceBread is a perishable food with a short microbiological and physico-chemical shelf-life. The main microbiological alteration occurring into few days after baking is the “rope spoilage” caused by spore-forming bacteria originating from raw materials. This phenomenon, often misinterpreted as a sign of unsuccessful dough leavening and not visible from outside, is more common under industrial production conditions during the hot season causing large economic losses in the warm climates of Mediterranean countries, Africa and Australia. The use of sourdough often controls this alteration even if the industrial application of this traditional process is limited by the long leavening times. In this study, an innovative procedure for the preparation of yeast-leavened bread comprising the addition of a fermentation product from Lactobacillus brevis grown in a flour-based medium has been applied. The resulting fermentation product (LbBio bioingredient) acts as a sourdough acidifying the dough and improving the textural, physico-chemical and microbiological properties of the resulting bread. The application of bioingredient LbBio could represent an innovative strategy in industrial bread production to obtain acidified yeast-leavened products, thus, preventing the ropy spoilage and reducing the negative effects of bran addition.     

Moisture diffusivity and shrinkage of broad beans during bulk drying in an inert medium fluidized bed dryer assisted by dielectric heating

Drying behavior of broad beans (Vicia faba) was studied in a pilot scaled fluidized bed dryer with inert particles assisted by dielectric heating. The effective diffusion coefficient of moisture transfer was determined by Fickian method at four different air drying temperatures of 35, 45, 55 and 65 °C. Correlations for moisture diffusivity as a function of moisture content and temperature of the drying medium were developed. The values of moisture diffusivity were obtained within the range of 1.27 × 10^?9–6.48 × 10^?9 m²/s and the activation energies for FBD and FBD + DE were found to be 27.71 and 17.10 kJ/mol, respectively. The shrinkage behavior of the broad beans was also investigated by considering the volume ratio of (V/V_O) to be function of moisture content alone and fitting a polynomial of the third order. The dielectric heating power was also found to be effective on the rate of drying.     

Monitoring nisin desorption from a multi-layer polyethylene-based film coated with nisin loaded HPMC film and diffusion in agarose gel by an immunoassay (ELISA) method and a numerical modeling

Polyethylene-based films coated with nisin loaded HPMC films were put in contact with food simulants, i.e. agarose gels with 5 or 30% (w/w) fat. Nisin desorption from the multi-layer films and diffusion in agarose gels were monitored by ELISA (Enzyme Linked ImmunoSorbent Assay). The data obtained after 2 or 6 days of contact between antimicrobial films and agarose gels were employed to determine nisin mass transfer by numerical modeling following Fick's second law. The values were in the range from 0.87 × 10^? 3 m s^? 1 to 4.30 × 10^? 3 m s^? 1 and 6.5 × 10^? 11 m² s^? 1 to 3.3 × 10^? 10 m² s^? 1, for nisin apparent desorption and diffusion coefficients, respectively. The diffusion process was governed by interactions between food matrix simulant and nisin. Moreover, it was observed that the polymer in the coating did not modify plastic film initial mechanical resistance and water vapor permeability.Industrial relevanceThis paper concerns active packaging, considered as a new approach to preserve food shelf life. Active packaging is a real gain for plastic and Food industrials. The paper deals with coating as a manner to activate packaging. The impact of coating on film properties is investigated.Also, predictive models are proposed to determine antimicrobial agent desorption and diffusion during some storage conditions.     

HPLC of proteose peptones for evaluating ageing of packaged pasteurized milk

The proteolysis of casein (CN) occurring in packaged pasteurized milk (PM) during refrigerated storage was studied with relation to hygienic and microbiological characteristics of starting raw milk. Six batches of raw milk having standard plate count (SPC) from 1.5×10⁴ to 2.5×10⁵ cfu mL⁻¹ and somatic cell count (SCC) from 1.6×10⁵ to 4.4×10⁵ units mL⁻¹ were pasteurized (73 °C for 15 s), packaged and stored at 4 °C for 12 days. Capillary zone electrophoresis of CN showed breakdown of β-CN in all PM samples during storage. An HPLC method for monitoring proteose peptones (PP) formation was developed. Level of PP in PM samples increased, with keeping time from 667–789 to 947–1383 mg L⁻¹ and PP formation was significantly (P<0.05) related to SCC of starting raw milk. Electrospray ionization–mass spectrometry showed that PP were mainly represented by PP-5 from either A¹ or A² variants of β-CN. Five commercial samples of PM were analysed for PP formation during 14-day storage at 4 °C. Commercial samples prepared by microfiltration process or bactofugation combined with pasteurization showed the slowest formation of PP. The effect of storage temperature on PP formation was evaluated by keeping a conventional PM sample at either 8 or 12 °C for 12 days. Proteolysis of all major CNs upon action of plasmin and bacterial proteinases was observed under these conditions. PP level thus proves to be a reliable analytical index for evaluating the ageing of packaged PM during refrigerated storage.     

Effect of ultrasound on the mass transfer and physical changes in brine bell pepper at different temperatures

Mass transfer and physical attributes of red bell pepper were evaluated. Pepper strips were placed into brine of constant concentration at different temperatures (25–55 °C) with immersion times ranging from 15 to 480 min with and without ultrasound treatment. Diffusion coefficients were evaluated for calcium, sodium, citric acid, soluble and total solids, impregnation and water loss. Firmness, kinetic coefficients and color were determined for each treatment. Ultrasound increased the uptake of solutes (p < 0.05) with the exception of calcium, sodium ions, and acidity, where diffusion coefficients did not significantly differ among treatments. Loss of water, total and soluble solids in tissue significantly increased at 55 °C with 47 kHz, with diffusion coefficients of 13.23 × 10⁻¹⁰ m²/s, 7.26 × 10⁻¹⁰ m²/s and 14.42 × 10⁻¹⁰ m²/s, respectively. These increases may be attributed to increased cell wall permeability, facilitating transport of water and solute, as evidenced by product firmness, where ultrasound treatments had a negative effect on firmness.     

Antimicrobial plastic film: Physico-chemical characterization and nisin desorption modeling

Antimicrobial active films represent an innovative concept in food packaging, developed to answer to consumer's expectation for better microbiological safety. In this study, the growth of pathogenic micro-organisms on the surface of food is proposed to be controlled by coating, on the surface of polyethylene/polyamide/polyethylene film (PE/PA/PE), a film-forming solution containing Nisaplin, a commercial form of bacteriocin produced by Lactococcus lactis subsp. lactis: nisin. The bioactivity of these multi-layer films coated with Nisaplin loaded HydroxyPropylMethylCellulose film is based on the release of this antimicrobial molecule towards a food simulant. Nisin mass transfer was studied and modeled, for different operating conditions, generally encountered in food products. pH didn't seem to interfere with nisin release kinetics, while the variation of NaCl concentration between 0.8% and 3.2% decreased the desorption coefficient (k_d) by 18% and the temperature increase from 10 °C to 28 °C resulted in an increase of k_d from 1.78 × 10^? 2 m s^? 1 to 2.10 × 10^? 2 m s^? 1. Coating of PE/PA/PE film with this antimicrobial layer induced little mechanical properties modifications without compromising industrial applications. Water barrier capacity was not altered.Industrial relevanceThis paper concerns active packaging, considered as a new approach to preserve food shelf life. Active packaging is a real gain for plastic and Food industrials. Coating was used to obtain antimicrobial packaging. The impact of coating on film characteristics is investigated.Also, antimicrobial agent desorption is determined during storage conditions.     

Fermentative ability of alginate-prebiotic encapsulated Lactobacillus acidophilus and survival under simulated gastrointestinal conditions

Lactobacillus acidophilus was encapsulated in alginate-inulin-xanthan gum and its ability to grow in carrot juice and survive 8 weeks of storage at 4 °C and subsequent exposure to artificial gastrointestinal conditions were assessed. Encapsulation significantly enhanced cell viability after fermentation and storage (6 × 10¹² and 4 × 10¹⁰ cells/ml versus 4 × 10¹⁰ and 2 × 10⁸ for free cells, respectively). Encapsulation protected L. acidophilus from exposure to simulated gastric conditions; minor alterations in viability and the protein profile occurred after incubation in pancreatic juice. For free cells, viability decreased significantly and the expression of numerous proteins was lost after incubation in gastric and pancreatic juice. Thus, encapsulation preserved probiotic bacterial viability and activity; the addition of inulin as a prebiotic component could enhance the functional properties of food products containing this formulation.     

Modelling thermal degradation of zearalenone in maize bread during baking

The thermal degradation of zearalenone (ZEA) was investigated using a crust-like model, representing maize bread, which was prepared with naturally contaminated maize flour. Model samples were heated under isothermal conditions at the temperature range of 100–250°C. No reduction was observed at 100°C. Thermal degradation rate constants (k) were calculated as 0.0017, 0.0143 and 0.0216?min^?1 for 150, 200 and 250°C, respectively. Maize bread baked at 250°C for 70?min was used to test the capability of model kinetic data for the prediction of ZEA reduction. The time–temperature history in the crust and crumb parts was recorded separately. Partial degradation of ZEA at each time interval was calculated by means of the corresponding k-values obtained by using the Arrhenius equation, and the total reduction occurring at the end of the entire baking process was predicted. The reduction in the crumb and crust of bread was also experimentally determined and found to be consistent with the predicted values. It was concluded that the kinetic constants determined by means of the crust-like model could be used to predict the ZEA reduction occurring during baking of maize bread.