Survival of Listeria monocytogenes in Galotyri,a traditional Greek soft acid-curd cheese,stored aerobically at 4°C and 12°C

Galotyri is a traditional Greek soft acid-curd cheese, which is made from ewes’ or goats’ milk and is consumed fresh. Because cheese processing may allow Listeria monocytogenes post-process contamination, this study evaluated survival of the pathogen in fresh cheese during storage. Portions (0.5 kg) of two commercial types (<2% salt) of Galotyri, one artisan (pH 4.0±0.1) and the other industrial (pH 3.8±0.1), were inoculated with ca. 3 or 7 log cfu g⁻¹ of a five-strain cocktail of L. monocytogenes and stored aerobically at 4°C and 12°C. After 3 days, average declines of pathogen's populations (PALCAM agar) were 1.3–1.6 and 3.7–4.6 log cfu g⁻¹ in cheese samples for the low and high inocula, respectively. These declines were independent (P>0.05) of the cheese type or the storage temperature. From day 3, however, declines shifted to small or minimal to result in 1.4–1.8 log cfu g⁻¹ of survivors at 28 days of storage of all cheeses at 4°C, indicating a strong “tailing” independent of initial level of contamination. Low (1.2–1.7 log cfu g⁻¹) survival of L. monocytogenes also occurred in cheeses at 12°C for 14 days, which were prone to surface yeast spoilage. When ca. 3 log cfu g⁻¹ of L. monocytogenes were inoculated in laboratory scale prepared Galotyri of pH ≅4.4 and ≅3% salt, the pathogen died off at 14 and 21 days at 12°C and 4°C, respectively, in artisan type cheeses fermented with the natural starter. In contrast, the pathogen survived for 28 days in cheeses fermented with the industrial starter. These results indicate that L. monocytogenes cannot grow but may survive during retail storage of Galotyri despite its low pH of or slightly below 4.0. Although contamination of Galotyri with L. monocytogenes may be expected low (<100 cfu g⁻¹) in practice, that long-term survival of the pathogen in commercial cheeses was shown to be unaffected by the artificial contamination level (3 or 7 logs) and the storage temperature (4°C or 12°C), which should be a concern.     

Dynamics of the loss and emergence of volatile compounds during the concentration of cashew apple juice (Anacardium occidentale L.) and the impact on juice sensory quality

Concentrating cashew apple juice alters the beverage aroma and flavor, compromising consumer acceptability of the concentrated beverage. To understand the mechanisms involved in these changes, this research characterized the dynamics of the loss and emergence of volatile compounds during cashew apple juice concentration, reporting their impact on beverage sensory quality. Fresh cashew apple juice (10.3°Brix) was concentrated in a thermal-siphon type evaporator operating in a closed system. Five samples were taken throughout the concentration process with the following soluble solids contents: 11.8°Brix, 14.9°Brix, 20.2°Brix, 29.6°Brix and 42.1°Brix. Trained judges rated the aroma note intensities, described as “fresh cashew apple” and “cooked” as perceived in the fresh and concentrated beverages. The headspace volatiles of the six samples were identified and quantified by GC–MS. The results indicated the esters as the major component in the fresh juice (226.46 μg kg^− 1) representing 45.0% of the total mass of volatiles, followed by the terpenes (118.98 μg kg^− 1), acids (45.23 μg kg^− 1), aldehydes (39.10 μg kg^− 1), alcohols (18.91 μg kg^− 1), lactones (19.15 μg kg^− 1), hydrocarbons (18.02 μg kg^− 1) and ketones (11.05 μg kg^− 1). Predictive statistical models (R² > 0.956, p ≤ 0.002) revealed that on reaching 14.9°Brix, the ester concentration declined more than 90%, the terpene content almost 100%, alcohols 85%, aldehydes 80% and hydrocarbons 90%. At 14.9°Brix, the intensity of “fresh cashew apple” aroma still predominated in the juice, but the panelists detected the presence of a weak “cooked” aroma. Concentration of the beverage to 20.2°Brix or above expressively increased the cooked aroma intensity and the concentration of hydrocarbons, alcohols and some aldehydes usually associated with off-flavors such as pentanal and decanal. This raises the possibility that some of these compounds might have been formed during juice processing. Juice with better sensory quality could possibly be obtained by concentrating the beverage to levels below 20.2°Brix, recovering the esters that evaporated off the juice until ~ 15°Brix is reached, and re-adding them to the juice concentrated.     

Influence of pH and NaCl on monolaurin inactivation of Streptococcus iniae

Streptococcus iniae, a Gram-positive bacterium, has been recognized as a cause of human and fish streptococcosis. Aquacultured fish are susceptible to infection and have been epidemiologically linked with wound infections of fish handlers. Therefore, there is a need to develop methods of prevention and/or control of this pathogen. This study determined the minimum inhibitory concentration of monolaurin (glycerol monolaurate) against S. iniae strains PW and BU and utilized gradient plates at 37°C to determine the combined influence of pH and NaCl on monolaurin inactivation of S. iniae. The minimum inhibitory concentration of monolaurin against strain PW was 12.4±0.3 μg ml⁻¹ and against strain BU was 12.1±0 μg ml⁻¹. Compared to growth in the absence of monolaurin, the incorporation of 6 μg ml⁻¹ monolaurin into the salt (1.12–6.95%)–pH (4.26–8.88) gradient plates prevented growth of strain PW at pH values <6.00 and strain BU at pH values <6.20, regardless of the salt concentration. The combination of monolaurin with environmental variables such as pH and salt proved to be an effective tool for in vitro control of S. iniae.     

Antimicrobial agent detection in ewes’ milk by the microbial inhibitor test brilliant black reduction test—BRT AiM®

The detection limits of 24 antimicrobial agents were determined in ewes’ milk by one commercially available version of brilliant black reduction test, BRT Inhibitor Test with prediffusion AiM^® (BRT AiM^®). For each drug, eight concentrations were tested on 20 milk samples from individual ewes. The detection limits of the BRT AIM^® method were determined by means of logistic regression models: 6 μg kg⁻¹ amoxycillin, 6 μg kg⁻¹ ampicillin, 51 μg kg⁻¹ cloxacillin, 2 μg kg⁻¹ penicillin “G”, 230 μg kg⁻¹ cefadroxil, 1330 μg kg⁻¹ cephalosporin “C”; 270 μg kg⁻¹ cephalexin, 92 μg kg⁻¹ cefoperazone, 120 μg kg⁻¹ ceftiofur, 69 μg kg⁻¹ cefuroxime, 6000 μg kg⁻¹ streptomycin, 1200 μg kg⁻¹ gentamycin, 3700 μg kg⁻¹ neomycin, 630 μg kg⁻¹ erythromycin, 120 μg kg⁻¹ tylosin, 390 μg kg⁻¹ doxycycline, 5500 μg kg⁻¹ oxytetracycline, 6200 μg kg⁻¹ tetracycline, 5400 μg kg⁻¹ sulfadiazine, 3200 μg kg⁻¹ sulfamethoxazole, 6500 μg kg⁻¹ sulfamethoxypyridazine, 6200 μg kg⁻¹ sulfaquinoxaline, 22000 μg kg⁻¹ chloramphenicol and 4100 μg kg⁻¹ trimethoprim. The BRT AiM^® method presents detection limits for β-lactam antibiotics that are similar to those obtained as Maximum Residue Limits (MRLs) according to Regulation 2377/90 EEC as set out by the European Union. However, for other antimicrobial agents the estimated limits were higher than those of the EU-MRLs. It is therefore advisable to enhance the sensitivity of the method for the detection of the different antimicrobial groups or to develop a combined system of different microbiological inhibitor tests that would enable the detection of a greater number of antimicrobial agents.     

Biochemical changes throughout the ripening of a traditional Spanish goat cheese variety (Babia-Laciana)

The physico-chemical characteristics, proteolysis (classical nitrogen fractions, caseins and their degradation products and free amino acids), and lipolysis (fat acidity and free fatty acids) were studied throughout the ripening of three batches of Babia-Laciana cheese, a Spanish traditional variety made from raw goats’ milk. The main compositional characteristics of this cheese at the end of the ripening are its high content of total solids (TS) (78.0±2.4 g 100 g⁻¹ of cheese) and fat (61.1±1.2 g 100 g⁻¹ of TS), the presence of residual lactose (1.6±0.8 g 100 g⁻¹ of TS) and its low content of sodium chloride (1.1±0.7 g 100 g⁻¹ of TS) and ash (2.8±0.5 g 100 g⁻¹ of TS). Its pH values (4.44±0.72) are extraordinarily low. The evolution and final values of the different nitrogen fractions show that this cheese undergoes a very slight proteolysis, a fact which was corroborated when the caseins and their degradation products were quantified: β-casein did not undergo any modification throughout ripening, while only 21% of the α_s-caseins were degraded. Free amino acids content increased by a factor of about 7 throughout ripening, resulting in a high content of γ-amino butyric acid and a low content of glutamic acid at the end of the process. Fat acidity increased very slightly, approximately 4.5 times, during ripening, reaching final values of 3.5±2.2 mg KOH g⁻¹ of fat. The total free fatty acids content showed a similar evolution to fat acidity. At the end of the ripening process, the main free fatty acid was C_18:1, followed by C₁₆ and C₁₀.     

Macro- and microelement contents in fruiting bodies of wild mushrooms from the Notecka forest in west-central Poland

Fruiting bodies of wild mushrooms and forest soil samples were collected and analyzed for macro- (N, P, K, S, Ca, Mg) and microelement (Al, Zn, Fe, Mn, Cd, Pb) contents in pine stands of the Notecka Forest in west-central Poland. Elements were determined by atomic absorption spectrometry in 160 samples of 8 fungal species and 15 underlying soil samples. Macro- and microelement contents in soil were low and characteristic of the poor and acidic sandy soils of the Polish lowlands not influenced by industrial pollution. In fruiting bodies, the highest mean concentration of macroelements (dry mass basis) was found for N (40.0 g kg⁻¹), followed by K (33.0 g kg⁻¹), P (5.4 g kg⁻¹), S (2.2 g kg⁻¹), Ca (1.0 g kg⁻¹) and Mg (0.7 g kg⁻¹). All macroelements (except for Ca) were concentrated in considerably higher levels in the fruiting bodies than in the forest soil. Nitrogen, P, K, S and Mg were preferably translocated into the cap rather than the stipes. Calcium, however, was often found in higher concentration in stipes than in caps. The mean microelement concentrations, across all tested fungi, were in the following order: Al > Zn > Fe > Mn > Pb > Cd. Microelements showed different distributions, depending on the part of the fruiting body. Some were more concentrated in the caps and some in stipes and distributions varied among species. Xerocomus badius is the most often harvested edible mushroom in the Notecka Forest. Pb and Cd distributions in fruiting bodies of this mushroom were evaluated in order to assess health risks to consumers. The estimated dietary exposures to Pb and Cd for consumers of this mushroom were in excess of guidelines on safe exposures.     

Inactivation of Escherichia coli O157:H7 by cinnamic aldehyde purified from Cinnamomum cassia shoot

Escherichia coli O157:H7 is a pathogen, which causes the hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura in humans. Control of the bacterial cells in foods is an important factor to reduce outbreaks of the foodborne diseases. In this study, cinnamic aldehyde possessing antimicrobial activity against the bacterial cells was purified from the extract of cinnamon (Cinnamomum cassia Blume) shoot by sequential fractionation with various solvents and silica gel column chromatography. When E. coli O157:H7 cells were incubated at 37°C for 12 h in the presence of 500 μg ml⁻¹ of the purified from cinnamic aldehyde, the viable counts decreased dramatically (from 4.9×10⁶ to 1.0×10² cfu ml⁻¹). In the presence of 1000 μg ml⁻¹ of the substance, most of the cells were killed after 2 h of incubation suggesting that the antimicrobial activity of cinnamic aldehyde is bacteriocidal in E. coli. Scanning electron microscopic observations revealed that the bacterial cells treated with the cinnamic aldehyde suffered from severe damages in their surface structure. Minimal inhibitory concentration of the cinnamic aldehyde was determined to be 250 μg ml⁻¹ against E. coli strains O157:H7 and O26 or 500 μg ml⁻¹ against strains ATCC11105 and O111.     

Efficacy of plant extracts in inhibitingAeromonas hydrophilaandListeria monocytogenesin refrigerated,cooked poultry

Alcohol extracts of angelica root, banana purée, bay, caraway seed, carrot root, clove (eugenol), marjoram, pimento leaf and thyme were applied to cooked chicken to determine their antimicrobial activities against Aeromonas hydrophilaand Listeria monocytogenes.Skinless chicken breast meat was cooked to an internal temperature of 85°C, allowed to cool to c. 5°C, then treated by surface application with plant extracts. Low (10 cfu g⁻¹)or high (10⁵ cfu g⁻¹)populations of A. hydrophilaand L. monocytogeneswere applied and samples were stored at either 5 or 15°C for up to 14 or 7 days, respectively. Eugenol and pimento extracts were most effective in inhibiting growth of both bacteria. A. hydrophilawas the more sensitive to the two treatments, with 4 log₁₀ cfu g⁻¹less growth occurring at 14 days at 5°C on eugenol-treated breast meat than on control samples. These results suggested that plant extracts might be useful as antimicrobials in cooked, ready-to-eat chicken meat.     

In-vitro mineral binding capacity of five fiber sources and their insoluble components for magnesium and calcium1

In-vitro binding of calcium (Ca) and magnesium (Mg) by total dietary fiber, hemicellulose A (HCL A), lignocellulose (LCL), cellulose (CL), and lignin (L) fractions isolated from rice bran (RB), wheat bran (WB), oat fiber (OF), apple fiber (AF) and tomato fiber (TF) was evaluated. At pH 6.8, significant amounts of Ca were bound by whole fibers, ranging from 800 μg g⁻¹ for RB to 10 097 μg g⁻¹ for TF. Mg bound by whole fibers varied from 496 μg g⁻¹ for OF to 2177 μg g⁻¹ for WB. Re-acid washing (pH<2.0) released 95–99% of the Ca and Mg bound to the fibers. Fibers with the highest endogenous Ca and Mg concentrations bound significantly (P<0.05) the highest amounts of the minerals studied. The Ca bound by HCL A varied from 9753 μg g⁻¹ for RB to 11 337 mg g⁻¹ for TF, whereas Mg bound varied from 1151 μg g⁻¹ for OF to 5626  μg g⁻¹ for TF hemicellulose fractions, respectively. Among the fiber components, Mg binding decreased in the order HCL A>LCL>L>CL, whereas Ca bound was in the order HCL A>LCL>CL>L. A relatively strong correlation was observed between the combined effects of protein content, hemicellulose, and lignin vs total Ca and Mg bound. 1998 Elsevier Science Ltd. All rights reserved     

Methyl ketone production from copra oil by Penicillium roqueforti spores

Bioconversion of copra oil by two strains of Penicillium roqueforti spores was studied in the presence or absence of exogenous lipase. Without exogenous lipase action, methyl ketone productivities were weak: 33 ± 1.9 to 61 ± 2.4 μmol g⁻¹ of oil, respectively, for strains 1 and 2. This formation results from the bioconversion of free fatty acids present in copra oil and appears strain-dependent. The major ketone was 2-undecanone, reflecting the high concentration of dodecanoic acid in the substrate. After lipolysis of copra oil by a Candida cylindracea lipase, a large increase of methyl ketone productivities (912 ± 13 and 1935 ± 26 μmol g⁻¹ of oil, respectively) is noticed with 2-heptanone predominating. This observation could result from the selectivity of the lipase used in the bioconversion process, or from the preferential oxidation due to spore specificity. When the reaction time was increased, the amount of methyl ketones decreased and other volatile compounds were formed..     

High-pressure and temperature effects on the inactivation of Bacillus amyloliquefaciens,alkaline phosphatase and storage stability of conjugated linoleic acid in milk

Milk rich in conjugated linoleic acid (CLA, 42 ± 3 mg g^− 1 fat) was used to evaluate the impact of high-pressure sterilization (HPS). The pressure, temperature and time needed to reduce 7-log of Bacillus amyloliquefaciens endospores were determined in the presence of nisin (4–64 mg L^− 1). In addition, the inactivation of alkaline phosphatase was evaluated. After HPS treatment, the remaining CLA and formation of hydroperoxides were monitored during storage up to 60 d at 25 °C. The addition of nisin (≥ 16 mg L^− 1) to milk significantly enhanced the inactivation of B. amyloliquefaciens (7-log reduction) after treatment at 600 MPa, 120 °C and 5 min of holding time. These conditions were selected to evaluate the impact of HPS on the CLA retention and hydroperoxides formation. Milk with the addition of nisin and treated with HPS delivered higher retention of CLA and a lower concentration of hydroperoxides compared with the UHT equivalent process (125 °C/15 s and 135 °C/10 s).Industrial relevanceHigh-pressure sterilization is a valuable alternative to produce superior quality milk products in cases where traditional thermal treatments have failed. This study evaluated the impact of processing conditions on the conjugated linoleic acid content at conditions where commercial sterilization has been achieved (7-log reduction of B. amyloliquefaciens). The outcomes of this study are considered as a step further for the development of high-pressure sterilized milk.     

Available lysine,protein digestibility and lactulose in commercial infant formulas

Available lysine, in vitro protein digestibility and lactulose values were determined in 23 commercial infant formulas. The mean available lysine content of the formulas based on dairy proteins was 66.7±9.5 mg g⁻¹ protein, similar to that of human milk, while that of soy based formulas was considerably lower (45.0±8.3 mg g⁻¹ protein). In vitro protein digestibility values ranged 85.5–88.9% for soy-based formulas and 90.5–98.3% for formulas based on dairy proteins. Formulas based on milk enriched with whey had higher lactulose content than those based on cow's milk. However, all values were below the limit of 600 mg L⁻¹ recommended for UHT milk.     

Chemical composition and potential of some underutilized tropical biomass. I: fluted pumpkin (telfairia occidentalis)

The seeds of Telfairia occidentalis have been subjected to standard chemical analysis to evaluate their properties. Proximate analysis indicated a low moisture content (6.30 ± 0.50%). The ash content was slightly higher than the range recommended for compounding of animal feed (3.44 ± 0.06%). The carbohydrate content was low (16.5 ± 0.12%). Starch, however, constituted the dominant carbohydrate (62.5 ± 0.48), while three sugars, glucose, fructose and sucrose were detected in the seed. The crude protein in the seed was high (16.0 ± 0.03%), a value which compared favourably with high protein seeds and nuts. In all, 16 amino acids were detected in the protein. Glutamic acid showed the highest concentration (16.4 g 100 g⁻¹), while lysine showed the lowest (2.6 g 100 g⁻¹). The brown oil extracted from the seed (yield 48.6 ± 0.94) had the following physicochemical properties; acid value, 3.05 ± 0.80 g, saponification value 166 ± 1.34 mg/KOH g⁻¹, free fatty acids, 0.3 g and peroxide value 3.02 ± 0.07 mg Eq kg⁻¹. The iodine value (80.1 ± 0.10)g 100 g⁻¹ indicated a preponderance of unsaturated fatty acid. Four fatty acids were detected whilst unsaturated acids constituted 61.3 g. Triglyceride was the dominant lipid species while hydrocarbons, waxes, sterols and sterol esters and higher alcohols, were detected in the unsaponifable matter. Results of nutritionally valuable mineral elements indicated that potassium occurred at the highest concentration.     

The effect of fat content on the rheology,microstructure and heat-induced functional characteristics of Cheddar cheese

Cheddar cheeses with the different fat contents were made in triplicate and ripened at 4°C for 30 d and at 7°C for the remainder of the 180-d investigation period. The cheeses were designated: full-fat (FFC), 300 g kg⁻¹; reduced-fat (RFC), 219 g kg⁻¹; half-fat (HFC), 172 g kg⁻¹; and low-fat (LFC), 71.5 g kg⁻¹. A decrease in the fat content from 300 to ≤172 g kg⁻¹ resulted in significant (P<0.05) decreases in contents of moisture in non-fat substance and pH 4.6 soluble N (expressed as % total N), and increases in the contents of moisture, protein, intact casein and free amino acids. Reduction in fat content resulted in an increase in the volume fraction of the casein matrix and a decrease in the extent of fat globule clumping and coalescence. The mean values of fracture stress and firmness for the FFC were significantly lower than those of the RFC and HFC, which had similar values; the values for the LFC exceeded the limits of the test and were markedly higher than those of the other cheeses at all times. On baking the cheese, reduction in fat content resulted in significant increases in the mean melt time (time required for shred fusion) and apparent viscosity and a decrease in the mean flowability of the melted cheese. The stretchability of the FFC increased most rapidly and, at ∼15 and 30 d, attaining mean values which were significantly higher than those of the other cheeses. Thereafter the stretchability of the FFC decreased progressively to values that were significantly (i.e. at 150 d) or numerically (i.e., at 180 d) lower than those of the RFC and HFC. At ripening times ≥15 and ≤90 d, the stretchability of the LFC was significantly lower than that of the RFC, and significantly or numerically lower than the HFC.     

Production of volatile aroma compounds by kefir starter cultures

Production of carbonyl compounds by single-strain cultures, kefir starter (Lactobacillus delbrueckii subsp. bulgaricus HP1+Lb. helveticus MP12+Lactococcus lactis subsp. lactis C15+Streptococcus thermophilus T15+Saccharomyces cerevisiae A13) and kefir grains during fermentation and storage of kefir was studied. The content of carbonyl compounds produced by kefir starter was greater than that produced by kefir grains. The maximum acetaldehyde concentration (18.3 μg g⁻¹) in kefir with starter culture was mainly due to the metabolic activity of Lb. delbrueckii subsp. bulgaricus HP1 isolated from kefir grains. The highest diacetyl production activity was recorded in the starter culture (1.87 μg g⁻¹) and the single-strain culture St. thermophilus T15 (1.62 μg g⁻¹), followed by Lb. helveticus MP12 (0.85 μg g⁻¹) and Lc. lactis subsp. lactis C15 (0.42 μg g⁻¹). The lactobacilli Lb. delbrueckii subsp. bulgaricus HP1 and Lb. helveticus MP12 produced acetone, which was not found in the cocci cultures. The presence of 2-butanone was related to the production ability of Lb. helveticus MP12. In comparison, Lc. lactis subsp. lactis C15 synthesized ethyl acetate more actively than the other single-strain cultures included in the starter. S. cerevisiae A13 produced ethanol and CO₂ in amounts (3975 μg g⁻¹; 1.80 g L⁻¹) that lent cultured kefir distinctive flavour and aroma characteristic of authentic kefir.     

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.     

Purification of angiotensin I-converting enzyme inhibitory peptides and antihypertensive effect of milk produced by protease-facilitated lactic fermentation

Fresh low-fat milk was fermented with five mixed lactic acid bacteria for up to 30 h at 42 °C. A protease, prozyme 6, was added 5 h after the beginning of fermentation. The whey was separated from the fermented milk and freeze-dried. As the fermentation time extended to 30 h, soluble protein content increased from 30.9 to 195.9 mg g⁻¹, free amino acid content increased from 2.8 to 192.8 mg g⁻¹, peptide content increased from 6.4 to 402.8 mg g⁻¹ and γ-aminobutyric acid (GABA) increased from 0 to 80.6 mg 100 g⁻¹, while inhibition of angiotensin I-converting enzyme (ACE) increased as indicated by a decrease of IC₅₀ from 1.18 to 0.24 mg mL⁻¹, respectively. The amino acid sequences of two ACE inhibitory peptides were Gly–Thr–Trp and Gly–Val–Trp, of which the IC₅₀ values were 464.4 and 240.0 μm, respectively. The systolic blood pressure and diastolic blood pressure of spontaneously hypertensive rat (SHR) were reduced 22 and 21.5 mm Hg, respectively, after 8 weeks of oral administration of diluted whey (peptide concentration 5 mg mL⁻¹) from the 30 h fermentation.     

Temperature effect on the biological activity of Bifidobacterium longum CRL 849 and Lactobacillus fermentum CRL 251 in pure and mixed cultures grown in soymilk

The influence of temperature on the growth and biological activity of two probiotic strains (Bifidobacterium longum CRL 849 and Lactobacillus fermentum CRL 251) as pure and mixed cultures in soymilk (SM) were evaluated. Maximum growth was observed at 37°C in both mixed and pure cultures. In a product prepared with the mixed culture (1:1) at 37°C, the amount of lactic acid produced was approximately 55 mmol l⁻¹ after 24 h with a slow production rate (2.8 mmol l⁻¹ h⁻¹); the formation of acetic acid was higher with respect to pure cultures (82.01 mmol l⁻¹ after 24 h), and final pH (24 h) was 5.0. About 85% of the total amount of sugars in SM was reduced, mainly sucrose. Stachyose was reduced (71%) after 4 h of incubation. Maximum activity of alpha-galactosidase (alpha-gal) (13.2 U ml⁻¹) was observed after 6 h. At 37°C the bifidobacterium strain was viable in mixed culture throughout the period assayed. At lower (30°C) or higher (42°C) temperatures, mixed culture showed slower growth and lower acid production in SM but the alpha-gal activity was stimulated at 30°C.     

Selenium analysis of selected Egyptian foods and estimated daily intakes among a population group

The selenium (Se) content of 67 local foods had been determined using electrothermal (ETAAS) and hydride generation (HGAAS) atomic absorption spectrometry. The richest sources of Se were chicken (323±35 μg kg⁻¹); eggs (166±19.4 μg kg⁻¹) and fish (306±5.2 μg kg⁻¹). Vegetables and fruits contained trace amounts of Se (1–33 μg kg⁻¹). Wide variations in Se content were reported between various bread types and values ranged from 14 (home-made bread) to 152 (flattened bread) μg kg⁻¹, respectively. The estimated adult Se intake was 49 μg kg⁻¹; bread being the major contributor (63.6%). ©     

Structural,thermal and viscoelastic characteristics of starches separated from normal,sugary and waxy maize

Starches separated from five types of maize (two normal, one sugary and two waxy) were investigated for physicochemical, thermal, amylopectin structure and viscoelastic properties. Kisan and Paras were normal maize while Parbhat and LM-6 were waxy maize type. Apparent amylose content of normal and sugary maize was 29.5–32.6 and 41.0%, respectively. Swelling power of normal, sugary and waxy maize starches was 11.6–15.2, 7.8 and 30.2–39.2 (g/g), respectively. X-ray diffraction of maize starches indicated typical A-pattern. Maize starch showed a single broad peak at 2θ=23.2° and a dual peak 2θ=17°–18.1, respectively. Waxy maize starches showed the presence of greater crystallinity than other starches while sugary maize starch showed the presence of lower crystallinity and a large amount of amylose–lipid complex. Intrinsic viscosity [η] of starches in 90% DMSO at 25 °C was 79.7–119.5 ml g⁻¹ for normal, 70.5 ml g⁻¹ for sugary and 107.2–118.1 ml g⁻¹ for waxy starches. Branch chain–length distribution of amylopectin revealed that the apparent amylose, long side chain- and short side chain-amylopectin proportion ranged between 0.0–41%, 13.4–31.5% and 41.5–66.8%, respectively, among the various maize starches. Maize sugary showed the highest apparent amylose content and the least amount of short- and long-side chains of amylopectin. LM-6 and Parbhat showed higher proportion of both long- and short-chain amylopectin as compared to other starches. Distribution of α-1, 4-chains of amylopectin (short-/long-chain) ranged between 2.1 and 3.4, the least for LM-6 and the highest for Paras starch. The transition temperatures (T_o–T_c) ranged between 60.5 and 76.1 °C for sugary, 63.5–76.3 °C for normal and 64.4–81.3 °C for waxy maize starch. The enthalpy of gelatinization (ΔH_gel) of sugary, normal and waxy maize starches was 2.47, 3.7–4.75 and 4.15–5.4 J/g, respectively. Normal and sugary maize starches showed higher G′ and G″ than waxy type starches. The change in the moduli during cooling and reheating of pastes cooked at different temperatures revealed low disintegration of granular structure in starch with higher amylose and amylose–lipid complex as well as low crystallinity. The changes in moduli during 10 h at 10 °C revealed highest retrogradation in maize sugary followed by Paras and Kisan starch.