Inhibition of Alicyclobacillus acidoterrestris spores by natural compounds

The aim of this study was to evaluate the antimicrobial effectiveness of some natural compounds (cinnamaldehyde, eugenol, limonene) and sodium benzoate against two strains of Alicyclobacillus acidoterrestris (c8 and γ4). The antimicrobial compounds (10–500 ppm) were solved in malt extract broth, inoculated separately with 10³ spores mL⁻¹ of each strain; the samples were incubated at 44 °C and the outgrowth of spores was evaluated every day by measuring the absorbance of the medium at 420 nm; inoculated samples without active compounds were used as controls. The results pointed out that limonene was not effective in inhibiting the outgrowth of A. acidoterrestris spores; 100 ppm of cinnamaldehyde or sodium benzoate slowed the spore germination, whereas 500 ppm of eugenol inhibited the growth of microbial targets for 13 days. Strain c8 was more resistant than isolate γ4 and cinnamaldehyde was the most effective compound in inhibiting the germination of A. acidoterrestris spores.     

Optimisation of pectin acid extraction from passion fruit peel (Passiflora edulis flavicarpa) using response surface methodology

Pectin was extracted from passion fruit peel using three different acids (citric, hydrochloric or nitric) at different temperatures (40–90 °C), pH (1.2–2.6) and extraction times (10–90 min), with and without skins using a 2⁴ factorial design. Temperature, pH and extraction time had highly significant effects on the pectin yield. A central composite design with face centring was used to optimise the extraction process conditions for citric acid without skins. Pectin yields varied from 10% to 70%. The optimal conditions for maximisation of pectin yield were the use of citric acid at 80 °C and pH 1 with an extraction time of 10 min considering model extrapolation.     

Minimization of aflatoxin M1 content in Iranian white brine cheese

A chemometric approach was used to minimize the aflatoxin M1 (AFM1) content of Iranian white brine cheese. The effects of processing factors such as renneting temperature (30–40°C), cutting size (0.5–1 cm), stirring time (10–20 min), press time (1–2 h), curd size (64–256 cm³) and saturated brine pH (4.6–6) on the AFM1 content of the cheese curds were explored. Renneting temperature, press time and saturated brine pH were, respectively, the most significant factors. The aflatoxin content of the cheese samples decreased with increasing renneting temperature and press time. Lowering of the saturated brine pH reduced AFM1 in the cheese curds. Taking account of all of the factors studied, optimum processing conditions for minimization of AFM1 in the cheese curds were: renneting temperature = 39.91°C, cut size = 0.51 cm, stirring time = 17.71 min, press time = 19.48 min, curd size = 73.27 cm³ and saturated brine pH = 4.79.     

Thermal resistance of Alicyclobacillus acidoterrestris spores in different heating media

The aim of this work was to study the influence of temperature (85, 90, 95 and 100 °C), total soluble solids (SS: 10 and 20°Brix or % by weight of sucrose) and pH (3.5 and 4.0) on decimal reduction time ( D- value) of the Alicyclobacillus acidoterrestris strain DSM2498 spores in apple juice, orange juice and malt extract broth (MEB). The effects of SS and pH on D -values and z- values in each media were insignificant ( P  > 0.05). In apple juice, orange juice and MEB, z- values of A. acidoterrestris for pH 3.5 and pH 4.0 were 12.2 ± 1.3–14.2 ± 3.2 °C, 11.2 ± 0.3–9.4 ± 0.0 °C and 11.9 ± 0.8–10.3 ± 0.4 °C, respectively. z- values of apple juice, orange juice and MEB samples with SS = 10°Brix and SS = 20°Brix were 14.1 ± 3.2–12.2 ± 1.3 °C, 10.2 ± 0.7–10.5 ± 1.1 °C and 11.3 ± 1.5–10.9 ± 0.2 °C, respectively. However, D -values of all samples were affected by temperature significantly ( P  < 0.01). Average D -values of apple juice, orange juice and MEB were 101.2 ± 14.7, 34.4 ± 7.9, 20.3 ± 4.9 and 4.3 ± 1.3 min for 85, 90, 95 and 100 °C. This study demonstrated that A. acidoterrestris spores exhibited high resistance to thermal processing applications. pH and SS of the media did not affect thermal resistance.     

Effect of pretreatment conditions on physicochemical parameters of carrot juice

Carrot juice obtained by hydraulic press with wooden set-up was subjected to pretreatments (temperature, time and pH) prior to extraction process. Their effects on the most important quality parameters of carrot juice, such as beta-carotene, reducing sugars, pectin, vitamin C, viscosity, pH and acidity were studied. Response surface methodology was employed, where the experiment was carried out according to a central composite rotatable design. The variables ranges used were 61.50–98.50 °C (temperature), 124.55–595.45 s (time) and 2.31–6.69 (pH – concentration of citric acid). The results showed that beta-carotene extraction was significantly increased (52.9%) with these pretreatments in comparison to control samples. All the derived mathematical models for the responses were found to be fit significantly to predict the data. The responses were optimised by numerical method and were found to be 7190 μg per 100 g beta-carotene, 3.41% reducing sugars, 4.96 mg per 100 g vitamin C, 0.59% pectin, 1.64 × 10³ Ns m⁻² viscosity, 5.26 pH and 4.97% acidity at optimum input variables of 75.26 °C (temperature), 349.89 s (time) and 3.2 (pH). The desirability for all the responses was found to be 83.8%.     

The thermal stability of Quorn™ pieces

Summary Quorn pieces were heat-treated at 90 °C, 100 °C and at various F values (equivalent time in minutes at a reference temperature of 121.1 °C) for 6.2–24 min and at different pHs (4.5–6.0). The heat-treated Quorn product was assessed for texture using a Voledkevich probe cell, weight change, and the sensory properties of tenderness, juiciness and overall acceptability. The processed and unprocessed Quorn pieces were examined by electron microscopy. Temperature and pH were found to influence sensory tenderness but not instrumental texture. pH also influenced water absorption. However, in general Quorn pieces were found to be stable to heat processing at 90 °C, 100 °C and 120 °C.     

Rennin-like milk coagulant enzyme produced by a local isolate of Mucor

Among 20 isolates of Mucor isolated from various environments in Jordan and found to produce a rennin-like acid protease, known as Mucor rennin-like enzyme (MRE), Mucor J20 was found to produce the highest level of MRE. The optimum incubation conditions for enzyme production in a fortified wheat bran mixture using solid-state fermentation were 3–4 days at 30°C. The highest MRE activity (185–200 rennin units or RU) was produced in a medium containing wheat bran and lentil straw (1 : 1 w/w) moistened with whey, and incubated in clay pots at 30°C for 4 days. A slightly lower activity value (178 RU) was found when using a mineral salt solution or distilled water instead of whey, or when using wheat bran alone with whey. At pH 4, the MRE retained its complete activity (100%) for 6 weeks at 5°C and 10°C, and for 3 and 2 weeks at 20°C and 30°C, respectively. After heating at 60°C for 10 min, the enzyme lost its activity at all pH levels used (pH 2–8). The crude extract of MRE was successfully applied in the manufacture of a cheese curd.     

Edible Apple Film Wraps Containing Plant Antimicrobials Inactivate Foodborne Pathogens on Meat and Poultry Products

ABSTRACT:  Apple-based edible films containing plant antimicrobials were evaluated for their activity against pathogenic bacteria on meat and poultry products.  Salmonella enterica  or  E. coli  O157:H7 (10⁷ CFU/g) cultures were surface inoculated on chicken breasts and  Listeria monocytogenes  (10⁶ CFU/g) on ham. The inoculated products were then wrapped with edible films containing 3 concentrations (0.5%, 1.5%, and 3%) of cinnamaldehyde or carvacrol. Following incubation at either 23 or 4 °C for 72 h, samples were stomached in buffered peptone water, diluted, and plated for enumeration of survivors. The antimicrobial films exhibited concentration-dependent activities against the pathogens tested. At 23 °C on chicken breasts, films with 3% antimicrobials showed the highest reductions (4.3 to 6.8 log CFU/g) of both  S. enterica  and  E. coli  O157:H7. Films with 1.5% and 0.5% antimicrobials showed 2.4 to 4.3 and 1.6 to 2.8 log reductions, respectively. At 4 °C, carvacrol exhibited greater activity than did cinnamaldehyde. Films with 3%, 1.5%, and 0.5% carvacrol reduced the bacterial populations by about 3, 1.6 to 3, and 0.8 to 1 logs, respectively. Films with 3% and 1.5% cinnamaldehyde induced 1.2 to 2.8 and 1.2 to 1.3 log reductions, respectively. For  L. monocytogenes  on ham, carvacrol films induced greater reductions than did cinnamaldehyde films at all concentrations tested. In general, the reduction of  L. monocytogenes  on ham at 23 °C was greater than at 4 °C. Added antimicrobials had minor effects on physical properties of the films. The results suggest that the food industry and consumers could use these films as wrappings to control surface contamination by foodborne pathogenic microorganisms.     

The use of response surface methodology to optimize the Maillard reaction to produce melanoidins with high antioxidative and antimutagenic activities

Response surface methodology was applied to determine the optimum conditions for the Maillard reaction so that high levels of antioxidative and antimutagenic substances could be produced from defatted soybean and corn starch hydrolysates. The optimum reaction conditions predicted to produce the greatest levels of active antioxidative and antimutagenic melanoidins were 155.0 °C for 6.3 h at a pH of 12.1 and 155.5–160.4 °C for 4.60–9.70 h at pH 10.4–12.5 respectively. The range of optimum reaction conditions to maximize melanoidin production were 148–170 °C for 3.0–7.5 h at pH values between 10.2 and 13.5. These predicted values for optimum reaction conditions were in good agreement with experimental values.     

Effect of heat treatment on curcuminoid, colour value and total polyphenols of fresh turmeric rhizome

Studies were undertaken to examine the effect of heat treatment on total phenolic content (TPC), colour value (yellowishness and brightness), polyphenol oxidase (PPO) activity and curcuminoid of fresh turmeric rhizome. Fresh turmeric rhizomes were subjected to heat treatment at different temperatures (60–100 °C) for different durations (10–60 min), causing a reduction in browning which was evident from the improved yellowishness and brightness. Activity of PPO was also decreased during heat treatment and PPO was almost inactivated when heated at 80 °C for 30 min. TPC of heat-treated turmeric after drying (powder) is significantly higher than that after the fresh process. TPC values increased gradually when samples were heated from 60 to 80 °C. At 90 and 100 °C, TPC values were almost identical. Maximum brightness and yellowishness were obtained when the turmeric was heated above 80 °C. Quantitation of curcuminoids in the turmeric sample was made with high performance thin layer chromatography (HPTLC). There was no significant change in the concentration of curcuminoids among the heat-treated samples. But in the sun-dried samples, a significant reduction in curcuminoid concentration was observed.     

Autolysis and biochemical properties of endogenous proteinases in Japanese sandfish (Arctoscopus japonicus)

Autolysis of Japanese sandfish ( Arctoscopus japonicus ) was studied. The highest autolysis was observed at 60 °C. Optimal pH for autolysis was found at both acidic and alkaline pH values. Autolytic activity decreased with increasing NaCl concentration. Further assay of the extract from Japanese sandfish exhibited the maximum activity at 55 °C and pH 9.5. The Japanese sandfish proteinases were markedly inhibited by pepstatin A at pH 3.5, while soybean trypsin inhibitor, PMSF and TLCK inhibited activities of proteinases at pH 9.5, suggesting Japanese sandfish proteinases were both aspartic and serine proteinases. The extracts were stable to heat treatment up to 50 °C for 15 min and still remained high relative activity after incubated at 50 °C for up to 8 h. Maximum stability of the extracts was observed between pH 6 and 11 and no changes of activity were found after incubation at pH 9.5 for up to 8 h. Activity of Japanese sandfish extract continuously decreased as NaCl concentration increased (0–30%), while activity increased as CaCl₂ concentration increased. The results suggest that major proteinases in Japanese sandfish were trypsin-like serine proteinases.     

Optimisation of osmotic dehydration of 'Tommy Atkins' mango fruit

Osmotic dehydration of mango in sucrose solution as influenced by temperature (30–50 °C), immersion time (60–150 min) and solution concentration (40–60% w/w) was studied through response surface methodology. Responses of water loss and solid gain were fitted to polynomials, with multiple correlation coefficients ranging from 0.72 to 0.95, respectively. The fitted functions were optimised for maximum water loss and minimised incorporation of solids in order to obtain a product resembling non-processed fruit. Optimum conditions to obtain water removal >25% with solid uptake lower than 6% could be obtained using a 44% (w/w) sucrose solution concentration, temperatures up to 38 °C and immersion times up to 80 min.     

Determination of optimum hazelnut roasting conditions

The objective of this study was to test the hypothesis that the roasting conditions used for hazelnuts, such as the air temperature, air velocity and roasting time (independent variables), could be optimized by using Response Surface Methodology. Effects of independent variables on sensory and physical characteristics were determined. A consumer test was used to determine the acceptable samples. Very dark and very light roasted samples, corresponding to 165 °C, 3 m/s, 25 min and 125 °C, 1 m/s, 15 min process conditions, respectively, were unacceptable. Superimposed contour plots were used to determine the values of independent variables and these showed the process conditions where all product characteristics were acceptable to consumers. At low velocity (0.3 m/s), acceptable products were produced at about 165–179 °C for 20–25 min. When air velocity increased, air temperature shifted to lower temperatures. Samples roasted at 145 °C, 2 m/s, 28 min, 165 °C, 1 m/s, 25 min and 145 °C, 3.7 m/s, 20 min produced the most acceptable products. The sample roasted at 165 °C, 1 m/s, 25 min required the least air velocity and was the most economical in terms of energy consumed among the samples rated most acceptable by consumers.     

Effect of polyphenol and pH on cocoa Maillard-related flavour precursors in a lipidic model system

Polyphenol and pH influence the flavour quality of cocoa beans during roasting. Amino acids and reducing sugars are flavour precursors in cocoa beans, which develop into cocoa-specific aroma through Maillard reactions during roasting. A central composite design was applied to determine the combined effect of polyphenol and pH on the flavour precursors during cocoa roasting at 120 °C for 45 min using a lipidic model system. Polyphenol was added at 40, 80 and 120 g kg⁻¹ and pH was adjusted to 4.5, 6 and 7.5. The response surface methodology revealed that a lower concentration of amino acids and reducing sugars was obtained at higher polyphenol concentration (120 g kg⁻¹) and lower pH value (4.5). Based on the constraints set, the best polyphenol concentration of 43–58 g kg⁻¹ and pH of 7.0–7.5 was found to be optimum for the formation of flavour precursors in this lipidic model study.     

Optimising conditions for enzymatic extraction of edible gelatin from the cattle bones using response surface methodology

This work was initiated to optimise the factors affecting the enzymatic extraction of edible gelatin from the cattle bones using response surface methodology. A central composite rotatable design was used to evaluate the effects of the enzyme concentration, time of enzymatic treatment and extraction temperature on the yield of extraction, gel strength, apparent viscosity and absorption at 420 nm. The R ² values of regression models for all the response variables were higher than 0.9. Data analysis showed that all the process variables significantly ( P  < 0.01) affected the gel strength and apparent viscosity of extracted gelatin, whereas the effect of extraction temperature on both yield of extraction and absorption at 420 nm was not significant ( P  > 0.05). Graphical optimum conditions for the extraction yield, gel strength, apparent viscosity and absorption at 420 nm were determined as 6.1 ppm, 15.6 h, 70 °C; 9.1 ppm, 11.9 h, 70.3 °C; 7.86 ppm, 14.9 h, 77.5 °C and 2.8 ppm, 10 h, 60 °C, respectively. For all the response variables, the experimental values were very close to the predicted values and were not statistically different ( P  < 0.05).     

Microbiological quality of ice creams commercialized in some cities in the state of Rio de Janeiro, Brazil

The microbiological quality of 60 ice cream samples of three commercial brands (A, B and C) of various flavours, commercialized in some towns in the State of Rio de Janeiro, Brazil, was evaluated. Total bacteria count (TCB), coliforms at 35°C (CT), coliforms at 44°C (CF) and presence of Staphylococcus aureus were performed on all samples. TCB ranged from 2.0 × 10 ² to 6.9 × 10 ⁵ cfu/mL, CT from < 3–≥ 2400 MPN/mL, CF from < 3–1100 MPN/mL and S. aureus from < 10–1.4 × 10 ⁶ cfu/mL. The level of bacterial contamination found in this study reflects the unhygienic conditions prevalent in manufacturing and storage of ice creams. Actions are thus necessary by the Brazilian regulatory agencies to require the ice cream processing plants to adopt quality guarantee systems, such as good manufacturing practices and hazard analysis and critical control points system.     

Texture of rehydrated dried bell peppers modified by low-temperature blanching and calcium addition

Diced green bell pepper was blanched twice, once at 51–79 °C for 19–61 min, and once at 95 °C for 3 min, and dried. The firmness of rehydrated samples was measured by puncture, and optimum conditions assessed by response surface methodology. The optimized model showed that, blanching at 65 °C for 49 min gave a 64% increase in puncture force over the control. The optimum temperature was used to evaluate the effect of adding CaCl₂. The dices were blanched twice, once at 65 °C for 3 min in either 0 or 4% CaCl₂, secondly in either 0 or 2% CaCl₂ solution at 95 °C for 3 min. In the second case the dices had been held at room temperature for 0–30 min before treatment. Adding CaCl₂ increased puncture force significantly ( P  ≤ 0.05). The best results, those which gave greatest firmness, were obtained by blanching at 65 °C for 3 min in 4% CaCl₂, holding for 16 min after blanching, followed by a secondary blanching at 95 °C in 2% CaCl₂.     

Encapsulation and stimulated release of enzymes using lecithin vesicles

Lecithin vesicles prepared by dehydration-rehydration (DR) were used to encapsulate enzymes (lysozyme and pepsin). The encapsulating efficiency was highest when the pH was close to the isoelectric point of each enzyme. Vesicles stored in suspension at 10°C for up to 21 days showed no release of enzymes. Acidic pH at 10°C and 25 mM Ca²⁺ at 10°C or 37°C produced pulse-like release of 17–35%, while acidic pH at 37°C produced pulse-like release followed by slow release up to 100%, and Tween 80 induced steady release from the beginning. The hydrolysis pattern of a protein by pepsin released from DR vesicles for 142 hr was similar to that obtained by the same total amount of fresh pepsin solution added stepwise, in proportion, indicating that the pepsin retains its activity throughout the period of encapsulation.
Vesicles prepared by processing of lecithin-enzyme solution by a homogenizer (Microfluidizer^TM) were also characterized and found effective.     

Processing factors affecting the osmotic dehydration of diced green peppers

A 2^5–2 fractional factorial design was used to investigate the effect of salt (2–10%), sorbitol (0–10%) concentration, agitation (0–80 r.p.m.), tissue to solution ratio (1:3 to 1:6) and temperature (20–50 °C) on weight loss, solids gain, salt and sorbitol uptake, water activity, tissue brix and solution brix, during osmotic dehydration (OD) of diced green peppers. Results showed that salt and sorbitol concentration were the most significant factors. In the first half hour of the osmotic process, salt and sorbitol significantly increased weight loss, solids gain and tissue brix, and decreased water activity. Temperature was also a significant factor. It increased weight loss during the first 2 h of the process, and decreased water activity after 20 h of osmosis. Agitation and tissue to solution ratio were less important.     

Preservation of minced pelagic fish by combined methods

The stability of unwashed and washed mince from Spanish sardines ( Sardinops sagax ) treated by mild heating, low pH (5.7–6.0), potassium sorbate (0.05–0.2%), and sodium chloride (2.0–6.0%) was studied. Addition of 6% salt and 0.2% sorbate at pH 5.7 was the best factor combination and when accompanied by heat treatment (10min, 80°C) produced a partly cooked product, microbiologically stable at 15°C for at least 15 d. Washing and mild heat treatment (2min, 80°C) helped to reduce the initial microbial load of the mince by a factor of 100 and, in combination with the above formulation, the product had a storage life of over 15 d at 15°C, compared with less than 3d for the original unwashed mince.