Response surface methodology for optimization of the mucilage extraction process from Pereskia aculeata Miller

In this report, a process for hydrocolloid extraction from Pereskia aculeata Miller (Barbados gooseberry), popularly known in Brazil as Ora-pró-nóbis (OPN), was developed. In the process, several operations, such as extraction, pressing, filtration, precipitation, grinding and drying, were required. The independent variables evaluated to determine the optimum extraction conditions were the ratio of water:raw material and the extraction temperature. The significant results at each stage were analyzed using the response surface method. The conditions that presented the highest precipitate yield, highest pH value, highest hue value (clear product), highest filtrate viscosity and minimum flow rate value were a water:raw material ratio of 2.46–3.70 L/kg and an extraction temperature between 54.6 and 80 °C. Using the optimized process, gums were prepared at different concentrations and the centesimal composition, mineral content, viscosity and emulsion formation capacities were analyzed. The stability of these emulsions was evaluated at room temperature and at 80 °C. The emulsion formation capacity of the product was verified as being proportional to the increase of the powder concentration. The OPN gums obtained at a solution concentration of 1 g/100 mL presented an emulsion formation capacity of 83%, and the increase in temperature reduced emulsion stability. The powdered product obtained was found to be close to yellow in color with high protein content and with functionalities that can be used in the food industry.     

Synthesis and partial characterization of octenylsuccinic starch from Phaseolus lunatus

Phaseolus lunatus starch was modified by esterification with octenyl succinic anhydride (OSA) and reaction effect evaluated in terms of chemical composition, gelatinization, pasting and emulsification properties. Succinylation was done using a 2³ factorial design with four replicates of the central treatment. Evaluated factors and levels were OSA concentration (1% and 3%), pH (7 and 9) and reaction time (30 and 60 min). Succinyl group percentage was the response variable. The optimum treatment was a reaction with 3% OSA at pH 7 for 30 min, which produced 0.5083% succinyl groups and 0.0083° of substitution. No significant changes were observed in proximate composition between the native and derivative starches. Apparent amylose level decreased notably from 32.4% to 23.6% due to OSA inclusion. Succinylation decreased starch gelatinization temperature (75.3–64.6 °C), decreased enthalpy (10.7–9.7 J/g), increased viscosity (700–1000 BU), increased emulsifying capacity (0.47–0.53 ml oil/ml sample), and made emulsions more stable over time. Starch modification did not, however, improve stability in heating–cooling processes.     

Extraction optimization of a hydrocolloid extract from cress seed (Lepidium sativum) using response surface methodology

Extraction conditions for maximum values of yield, viscosity and minimum protein content of hydrocolloid extract from Lepidium sativum seed were investigated using response surface methodology. A Central Composite Face Design (CCFD) with four independent variables: temperature (25–85 °C); pH (3–10); extraction time (10–25 min) and water to seed ratio (10:1–80:1) was used to study the response variables (yield, viscosity and protein content). Data analysis showed that all the variables significantly (p < 0.05) affected the extraction yield and viscosity, whereas the effect of water to seed ratio on protein content was not significant (p > 0.05). Applying a desirability function method the optimum parameters were: extraction temperature 35 °C, pH 10, water to seed ratio of 30:1 and an extraction time of 15 min. At this optimum point, apparent viscosity, yield and protein content were 0.2 Pa s, 6.46% and 0.57%, respectively. The experimental values were very close to the predicted values and were not statistically different (p > 0.05).     

Emulsification mechanisms and characterizations of cold, gel-like emulsions produced from texturized whey protein concentrate

A novel supercritical fluid extrusion (SCFX) process was used to successfully texturize whey protein concentrate (WPC) into a product with cold-setting gel characteristics that was stable over a wide range of temperature. It was further hypothesized that incorporation of texturized WPC (tWPC) within an aqueous phase could improve emulsion stability and enhance the rheological properties of cold, gel-like emulsions. The emulsifying activity and emulsion stability indices of tWPC and its ability to prevent coalescence of oil-in-water (o/w) emulsions were evaluated and compared with the commercial WPC80. The cold, gel-like emulsions were prepared at different oil fractions (φ = 0.20–0.80) by mixing oil with the 20% (w/w) tWPC dispersion at 25 °C and evaluated using a range of rheological techniques. Microscopic structure of cold, gel-like emulsions was also observed by Confocal Laser Scanning Microscope (CLSM). The results revealed that the tWPC showed excellent emulsifying properties compared to the commercial WPC in slowing down emulsion breaking mechanisms such as creaming and coalescence. Very stable with finely dispersed fat droplets, and homogeneous o/w gel-like emulsions could be produced. Steady shear viscosity and complex viscosity were well correlated using the generalized Cox–Merz rule. Emulsions with higher viscosity and elasticity were obtained by raising the oil fraction. Only 4% (w/w) tWPC was needed to emulsify 80% (w/w) oil with long-term storage stability. The emulsion products showed a higher thermal stability upon heating to 85 °C and could be used as an alternative to concentrated o/w emulsions and in food formulations containing heat-sensitive ingredients.     

Optimization of Hydrocolloid Extraction From Wild Sage Seed (Salvia macrosiphon) Using Response Surface

The effect of temperature (25–80°C), water to seed ratio (25:1–85:1) and pH (3–9) on the yield, apparent viscosity and emulsion stability index of wild sage seed hydrocolloid was investigated. The generated quadratic model showed that the optimum conditions for maximizing the responses were when temperature was 25°C, water to seed ratio was 51:1 and pH was 5.5. All hydrocolloid solutions (1% w/v) showed shear thinning behavior in different extraction conditions, consistency coefficient and flow behavior index varied from 4.455 to 9.435 (Pa.sⁿ), and 0.317 to 0.374, respectively. Besides, the chemical compositions of the seed and extracted gum were determined at optimal conditions.     

Influence of heat processing on functional properties of Australian wattle seed (Acacia victoriae Bentham) extracts

Whole wattle (Acacia victoriae Bentham) seed was extracted with water before or after a soaking/heat treatment regime designed to destroy its protease inhibitors. The yield, composition and physical properties of these extracts were measured and they were then subjected to an analysis of their functional properties, which included emulsion and foam formation and stabilization, solubility at different pH values and gelling ability. Processing of soaked wattle seed at 100 °C for 30 s led to a much reduced extract yield and viscosity at both pH 4 and 7, decreased its water-soluble carbohydrate content but increased its protein content, and solubility under alkaline conditions. Processing of wattle seed before extraction also led to increased emulsion droplet size and reduced emulsion stability, the differences being more pronounced in emulsions formed with 20% oil compared with 50% oil-in-water emulsions. Comparatively, the emulsions formed using extract from non-processed wattle seed were very stable at both 20% and 50% oil levels, especially at pH 7 where the enhanced viscosity of the extract predominated. All extracts had very low foaming capacity, and gelation did not occur in any of the samples even at 10% (w/v) extract concentration.     

Optimisation of mild-acidic protein extraction from defatted sunflower (Helianthus annuus L.) meal

For protein isolation from defatted sunflower meal, mild-acidic extraction was investigated to minimise concomitant oxidation and polymerisation of phenolic compounds and their irreversible binding to proteins. Because of the impaired solubility of sunflower proteins at low pH, the potential of sodium chloride (NaCl) to improve protein extractability was firstly screened for pH 2–11. Increasing NaCl concentrations of the aqueous solvent (c_NaCl) up to 2.8 mol/L enhanced the relative protein yield to almost 80% at ambient temperature and pH 5.6–7.4. As to improved protein recovery at minimal interactions with phenolic acids, the concerted effects of pH (3.2–7.4), c_NaCl (1–3 mol/L), temperature (T, 15–45 °C), and meal-to-solvent ratio (MSR, 0.03 and 0.05 g/mL) on the protein concentration of the extract (c_PE) and the relative protein yield (RPY) were examined, using response surface methodology (RSM). Aside from the prevailing influence of pH value and salt concentration, elevated temperature slightly enhanced protein extraction, whereas MSR mainly influenced c_PE, but hardly RPY. Calculated models proved suitable for the evaluation of extraction processes and the prediction of optimum conditions in terms of high protein yields at the lowest pH possible. Extraction at pH 6.0 was shown to be an appropriate compromise yielding 76–83% of the meal protein, depending on the constraints given. With elevated NaCl concentrations compensating for unfavourable pH conditions, mild-acidic extraction was found to be suitable for the recovery of high-quality sunflower protein in terms of light-coloured protein isolates.     

Biochemical and thermal characterization of crude exo-polygalacturonase produced by Aspergillus sojae

Crude exo-polygalacturonase enzyme (produced by Aspergillus sojae), significant for industrial processes, was characterized with respect to its biochemical and thermal properties. The optimum pH and temperature for maximum crude exo-polygalacturonase activity were pH 5 and 55 °C, respectively. It retained 60–70% of its activity over a broad pH range and 80% of its initial activity at 65 °C for 1 h. The thermal stability study indicated an inactivation energy of E_d = 152 kJ mol⁻¹. The half lives at 75 and 85 °C were estimated as 3.6 and 1.02 h, respectively. Thermodynamic parameters, ΔH^*, ΔS^* and ΔG^*, were determined as a function of temperature. The kinetic constants K_m and V_max, using polygalacturonic acid as substrate, were determined as 0.424 g l⁻¹ and 80 μmol min⁻¹, respectively. SDS-PAGE profiling revealed three major bands with molecular weights of 36, 53 and 68 kDa. This enzyme can be considered as a potential candidate in various applications of waste treatment, in food, paper and textile industries.     

Extraction of soybean isoflavones from soybean meal with aqueous methanol modified supercritical carbon dioxide

The effects of modifier composition in terms of methanol content in water, modifier concentration, meal particle size and extraction conditions (temperature, pressure and CO₂ flow rate) on isoflavones recovery from soybean meal by supercritical carbon dioxide (SC–CO₂) extraction were investigated. The highest isoflavones recovery attained was 87.3%, at 40 °C and 50 MPa, using CO₂ flow rate of 9.80 kg/h containing a modifier 7.8 mass% of 80% (v/v) aqueous methanol. Using different modifier concentrations (60–100% methanol) at 50 MPa and 40 °C, it was shown that 80% methanol was optimum for isoflavones extraction. In addition, isoflavones recovery increased with the modifier content in SC–CO₂ up to 10.2%. The optimal particle size was 20–30 mesh with bigger and smaller particles resulting in lower isoflavones recovery. The results showed that increasing the temperature from 40 to 70 °C drastically reduced isoflavones recovery at 50 MPa. The higher the extraction pressure, the higher was the isoflavones recovery. The extraction rate increased with CO₂ flow rate but the percentage recovery was more or less the same.     

Thermal behavior of emulsions manufactured with soy protein ingredients

The conformation, denaturation and aggregation behavior of proteins are important factors which dictate their ingredient functions and applications in formulated food products. The effect of variation in pre-treatment temperature (70–90 °C × 30 s), pH (6.4–7.5) and calcium supplementation (450 and 850 mg/L) on heat coagulation time (HCT at 140 °C) of model emulsions (3.6% (w/v) protein) stabilized with soy protein isolate (SPI) and soy protein hydrolysate (SPH) ingredients was determined. Generally, HCT of emulsions was not significantly affected by alteration of constituent pre-heating temperatures. Model emulsions displayed higher HCTs with increasing pH and lower levels of intrinsic ash content. At both supplementation levels, calcium addition led to decreased HCTs. Supplementation with chloride salts caused a greater decrease in HCT compared to supplementation with citrate salts. Furthermore, soy protein hydrolysis was associated with lower emulsion thermal stability. Results demonstrate that modification of ingredient and manufacturing parameters may be a useful approach for enhancing thermal stability properties of soy protein stabilized emulsions.     

Drying kinetics of grape seeds

Drying of grape seeds representing waste products from white wine processing (Riesling), red wine processing (Cab Franc), and juice processing (Concord) was studied at 40, 50, and 60 °C and constant air velocity of 1.5 m/s. Equilibrium moisture content had a significant effect on the normalized drying curve and was determined for each grape seed at each drying temperature. Effective moisture diffusivity ranged between 1.57 and 3.96 × 10⁻¹⁰ m²/s for Riesling seeds, 2.93–5.91 × 10⁻¹⁰ m²/s for Concord seeds, and 3.89–8.03 × 10⁻¹⁰ m²/s for Cab Franc seeds. The temperature dependence of the effective diffusivity followed an Arrhenius relationship, and the activation energies were 40.14 kJ/mol for Riesling seeds, 30.45 kJ/mol for Concord seeds, and 31.47 kJ/mol for Cab Franc seeds. Three thin-layer models were used to predict the drying curves: Page model, Lewis model, and the Henderson–Pabis model. All three models were found to produce accurate predictions compared to the mass average moisture loss for each grape seed variety (percent error less than 10%), and the Lewis model was shown to be an excellent model for predicting all three grape seed varieties (percent error less than 5%).     

Supercritical fluid extraction of β-carotene from crude palm oil using CO2

The aim of this study was to ascertain the influence of pressure, temperature and time on the supercritical fluid extraction of β-carotene from the crude palm oil. The operating conditions were shown as follows: pressures of 75, 125 and 175 bar, temperatures of 80, 100 and 120 °C and extraction time of 1, 3 and 5 h. The extracts were analyzed using UV spectroscopy at a wavelength of 450 nm. Then the experimental data was compared with the data obtained using a statistical method. The results from the model showed a good agreement with the experimental data. The results (obtained from the statistical model) demonstrate that a pressure of 140 bar, temperature of 102 °C and extraction time of 3.14 h are required to obtain optimum yield of β-carotene (1.028 × 10⁻²%) from the extraction process, however the maximum yield of the β-carotene (1.741 × 10⁻²%) was experimentally obtained at a pressure of 75 bar, temperature of 120 °C and extraction time of 1 h.     

Optimization of extraction process of crude polysaccharides from boat-fruited sterculia seeds by response surface methodology

Response surface methodology (RSM) was applied to optimize the extraction of crude polysaccharides from boat-fruited sterculia seeds. A central composite design was used for experimental design and analysis of the results to obtain the optimal extraction conditions. Extraction temperature, pH, extraction time and water to seed ratio were found to have a significant influence on the yield and purity of the extracted crude polysaccharides, while the three other factors except the water to seed ratio also significantly affected the relative viscosity. Based on the RSM analysis, optimum conditions were: temperature 60–65 °C, time 2.3–3.1 h, pH at 7.0 and water to seed ratio at 75:1. Under the optimized conditions, the experimental values were in close agreement with values predicted by the model. The crude polysaccharides prepared under optimum conditions contained 58.2% total carbohydrates (including uronic acids), 20% proteins, 9% moisture and 4.5% ash. The crude polysaccharides consisted of glucose (22.6%), rhamnose (10.0%), arabinose (7.9%), galactose (5.0%), xylose (0.8%) and galacturonic acid (11.8%).     

Viability of multi-strain mixtures of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 inoculated into the batter or onto the surface of a soudjouk-style fermented semi-dry sausage

The fate of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 were separately monitored both in and on soudjouk. Fermentation and drying alone reduced numbers of L. monocytogenes by 0.07 and 0.74 log₁₀ CFU/g for sausages fermented to pH 5.3 and 4.8, respectively, whereas numbers of S. typhimurium and E. coli O157:H7 were reduced by 1.52 and 3.51 log₁₀ CFU/g and 0.03 and 1.11 log₁₀ CFU/g, respectively. When sausages fermented to pH 5.3 or 4.8 were stored at 4, 10, or 21 °C, numbers of L. monocytogenes, S. typhimurium, and E. coli O157:H7 decreased by an additional 0.08–1.80, 0.88–3.74, and 0.68–3.17 log₁₀ CFU/g, respectively, within 30 days. Storage for 90 days of commercially manufactured soudjouk that was sliced and then surface inoculated with L. monocytogenes, S. typhimurium, and E. coli O157:H7 generated average D-values of ca. 10.1, 7.6, and 5.9 days at 4 °C; 6.4, 4.3, and 2.9 days at 10 °C; 1.4, 0.9, and 1.6 days at 21 °C; and 0.9, 1.4, and 0.25 days at 30 °C. Overall, fermentation to pH 4.8 and storage at 21 °C was the most effective treatment for reducing numbers of L. monocytogenes (2.54 log₁₀ CFU/g reduction), S. typhimurium (5.23 log₁₀ CFU/g reduction), and E. coli O157:H7 (3.48 log₁₀ CFU/g reduction). In summary, soudjouk-style sausage does not provide a favorable environment for outgrowth/survival of these three pathogens.     

Reduction of soybean oligosaccharides and properties of alpha-D-galactosidase from Lactobacillus curvatus R08 and Leuconostoc mesenteroides [corrected] JK55

This study was undertaken to investigate the potential for reducing non-digestive oligosaccharides (NDO) in soy foods, as well as the influence of exogenous conditions on intracellular α-galactosidase (α-Gal) producing lactic acid bacteria. Two strains, Lactobacillus curvatus R08 and Leuconostoc mesenteriodes JK55, showed the highest levels of raffinose degrading activity at over 40 U mL⁻¹, and presented maximum activities during the stationary phase in a medium where raffinose was the only carbon source. Raffinose was the most effective inducer, followed by melibiose, and galactose; the enzymes were partially inhibited by fructose and sucrose. On the other hand, limited activity was observed in glucose. The strains displayed optimum activity levels at neutral pH and a 35–37 °C temperature range. The α-Gal activities of L. curvatus R08 and Leu. mesenteriodes JK55 were maintained at pH 6.5–10.0. The activity of the α-Gal enzyme was stable in a relatively broad range of temperatures from 0 to 40 °C for 3 h. In soymilk, Leu. mesenteriodes JK55 and L. curvatus R08 completely hydrolyzed the NDO after 18–24 h of fermentation. The abilities of L. curvatus R08 and Leu. mesenteriodes JK55 to degrade raffinose sugars and, particularly, to produce organic acids from sugar, could contribute to reductions in the anti-nutritional properties of soy, and to the accumulation of compounds with beneficial properties during food processing. Furthermore, this study provides the optimum conditions to induce α-Gal from these strains.     

Effects of cooling temperature and hot carcass weight on the quality of lamb

The effects of cooling temperature (CT) (0–2, 2–4, or 4–6 °C) and hot carcass weight (HCW) (either 10.5 or 12.0 kg) on weight loss (WL) and meat quality were evaluated in 60 lamb carcasses of Rasa Aragonesa breed. Carcasses were exposed to CT throughout 90 h. WL was assessed at 18, 42, 66, and 90 h post-slaughter. pH, colour, instrumental measurement of texture, oxidation, and sensory parameters were evaluated in longissimus thoracis et lumborum aged for 96 h following standard methods. Sensory test involved a trained test panel. No significant interactive effects among the parameters evaluated were detected in the study. The lower the CT, the higher the WL after 90 h in storage (0.25% lost each 2 °C decrease), the higher final pH, and the lower lightness, the higher hue and chroma of the meat. Toughness was higher in meat cooled at 2–4 °C than in meat cooled at temperatures above or below this range. Neither oxidation nor sensory variables were affected by CT. Regarding on HCW, light carcasses exhibited higher WL (2.39% versus 2.04% after 90 h of cooling), higher final pH, and lower levels of oxidation than did heavier carcasses. Neither colour nor instrumental measurement of texture was affected by HCW. Lamb and fat odour and metallic and acid flavour intensities were significantly greater in the heavier carcasses, although it did not affect overall acceptability. Both CT and HCW should be considered as main effects on lamb quality, especially CT.     

Combined effects of thymol, carvacrol and temperature on the quality of non conventional poultry patties

The combined effect of thymol (0–300 ppm), carvacrol (0–300 ppm), and temperature (0–18 °C) on the quality of non conventional poultry patties packaged in air and modified atmosphere (MAP: 40% CO_2; 30%O₂; 30% N₂) was investigated using a simplex centroid mixture design. The patties were monitored for microbiological (total viable count, Enterobacteriaceae, lactic acid bacteria, Pseudomonas spp.) physico-chemical (pH, colour) and sensory attributes. For the patties mixed with the antimicrobials and stored at low temperature (0–3 °C) a reduction of the cell load of about 1–1.5 log cfu/g was observed. The log reduction was lower at the end of storage time and decreased with the increase of the temperature. For the poultry patties packaged in MAP the higher log reduction for Pseudomonas spp. during all the storage time was observed. In both packaging atmospheres the combination of the essential oils and low temperature determined no modification for off-odour during the first 4 days of storage.     

Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice

Rice is an important staple food in Asian countries. In rural areas it is also a major source of micronutrients. Unfortunately, the bioavailability of minerals, e.g. zinc from rice, is low because it is present as an insoluble complex with food components such as phytic acid. We investigated the effects of soaking, germination and fermentation with an aim to reduce the content of phytic acid, while maintaining sufficient levels of zinc, in the expectation of increasing its bioavailability. Fermentation treatments were most effective in decreasing phytic acid (56–96% removal), followed by soaking at 10 °C after preheating (42–59%). Steeping of intact kernels for 24 h at 25 °C had the least effect on phytic acid removal (<20%). With increased germination periods at 30 °C, phytic acid removal progressed from 4% to 60%. Most wet processing procedures, except soaking after wet preheating, caused a loss of dry mass and zinc (1–20%). In vitro solubility, as a percentage of total zinc in soaked rice, was significantly higher than in untreated brown rice while, in steeped brown rice, it was lower (p < 0.05). Fermentation and germination did not have significant effects on the solubility of zinc. The expected improvement due to lower phytic acid levels was not confirmed by increasing levels of in vitro soluble zinc. This may result from zinc complexation to other food components.     

Effects of the proteinaceous moiety on the emulsifying properties of sugar beet pectin

The role of the proteinaceous moiety in emulsifying was investigated using pectin from sugar beet as a model polysaccharide. Physicochemical and macromolecular characteristics of sugar beet pectin were examined with or without an enzymatic modification using multiple acid-proteinases. The enzymatic modification decreased the total protein content from 1.56±0.15% to 0.13±0.02% by the Bradford method without significant change in ferulic acid or most constitutional sugars. It also decreased the weight-average molecular weight (M_w) from 517±28 to 254±20 kg/mol and the z-average root-mean-square radius of gyration from 43.6±0.8 to 35.0±0.6 nm. Emulsifying properties of the polysaccharide with or without the enzymatic modification were evaluated by emulsion droplet size and creaming stability of O/W emulsions (pH 3.0) containing 15 w/w% middle-chain triglyceride and 1.5 w/w% sugar beet pectin as main constituents. The modification increased the average diameter (d_3,2) of emulsion droplets from 0.56±0.04 to 3.00±0.25 μm immediately after the preparation, suggesting a decrease in the emulsifying activity. It caused the creaming of the emulsions during incubation at 60 °C, which was in line with the finding that macroscopic phase separation occurred only in the presence of the modified pectin after storage at 20 °C for a day, suggesting a decrease in the emulsion stabilizing ability. The modification also decreased significantly the amount of the pectin fraction that adsorbed onto the surface of emulsion droplets from 14.58±2.21% to 1.22±0.03% and the interfacial concentration of the polysaccharide from 1.42±0.23 to 0.45±0.05 mg/m², where the proteinaceous materials in the pectin molecules activated the oil-water interface. Results from the present study suggest an important role of the proteinaceous moiety to explain the emulsifying properties of sugar beet pectin as in the case of gum arabic and soy soluble polysaccharide.     

Extractability of African yam bean (Sphenostylis stenocarpa) protein in acid, salt and alkaline aqueous media

Protein extractability from defatted Africa yam been (Sphenostylis stenocarpa) was studied under various conditions: solid/solvent ratio, time, pH, and salt. Extractable protein from S. stenocarpa was strongly dependent on all these factors. Maximum extractable protein was obtained after 2 h extraction time; the solid to solvent ratio in the range of 1:20–1:50 gave maximum protein extractability. The pH corresponding to maximum and minimum extractable proteins were 10 and 5, respectively, but addition of NaCl changed this slightly. Extractable protein of 92%, 88% and 84% were obtained in aqueous concentration of 0.01 MNa₂SO₄, 1.5 MNaCl and 0.01 MNaOH, respectively while other concentrations gave lower extractability. These salt concentrations, i.e. 0.01 MNa₂SO₄ and 1.5 MNaCl gave slightly lower extractable protein under alkaline condition. S. stenocarpa flour has a higher buffer capacity in acid medium than in alkaline medium.