Effect of Curd Washing Level on Proteolysis and Functionality of Low-Moisture Mozzarella Cheese Made with Galactose-Fermenting Culture

Abstract: The effect of curd washing on functional properties of low-moisture mozzarella cheese made with galactose-fermenting culture was investigated. A total of 4 curd washing levels (0%, 10%, 25%, 50% wt/wt) were used during low-moisture mozzarella cheese manufacture, and cheeses were stored for 63 d at 4 °C and the influence of curd washing on proteolysis and functionality of low-moisture mozzarella cheese were examined. Curd washing had a significant effect on moisture and ash contents. In general, moisture contents increased and ash contents decreased with increased curd washing levels. Low-moisture mozzarella cheese made with 10% curd washing levels showed higher proteolysis, meltability, and stretchability during storage than other experimental cheeses. In general, galactose contents decreased during storage; however, cheeses made with 25% and 50% curd washing levels had lower galactose contents than those with control or 10%. L*-values (browning) decreased and proteolysis increased in low-moisture mozzarella cheeses during storage.     

Effects of extended dry storage of powdered infant milk formula on susceptibility of Enterobacter sakazakii to hot water and ionizing radiation

Infant milk formula has been identified as a potential source of Enterobacter sakazakii, which has been implicated in neonatal meningitis and necrotizing enterocolitis. This study was undertaken to determine whether the length of E. sakazakii storage in powdered infant milk formula (PIMF) affected the ability of the pathogen to survive subsequent reconstitution of the powder with hot water or treatment with gamma radiation. Five E. sakazakii strains were mixed individually with PIMF and kept for up to 12 months at 25 degrees C. After storage PIMF was reconstituted with water at 60 to 100 degrees C or was exposed to < or = 5 kGy of gamma radiation. Without any treatment secondary to drying, E. sakazakii counts decreased < 1 log/g after 1 month but decreased about 4 log/g during storage for 8 to 12 months. Dry storage decreased thermal resistance but increased resistance of E. sakazakii to ionizing radiation in PIMF. Reconstitution of contaminated powder with water at 70 degrees C after 1 month of dry storage reduced E. sakazakii viability slightly, > 2 log/g, and after powder was stored for 12 months all E. sakazakii strains were eliminated. In contrast, desiccation substantially increased the resistance of E. sakazakii strains to ionizing radiation. Although the D-value for E. sakazakii IMF1 following overnight storage in PIMF was 0.98 kGy, > 4 kGy was required to kill 1.5 log/g of the same strain that had survived 12 months in dry PIMF. Results suggested that low-dose irradiation will more effectively eliminate E. sakazakii from PIMF if the treatment is applied shortly after PIMF manufacture.     

Population dynamics of Salmonella spp. and Shigella spp. in ready-to-eat Mediterranean vegetable salads

This study evaluated the behavior of Salmonella and Shigella (5–6 log CFU/g) in tomato–cucumber (TC) salad without additives (control), TC with 1.0% lemon juice and 0.5% salt, TC with 10% wt/wt tahini, coleslaw, and toum sauce at 4, 10, or 24°C for 5 days. At 4°C, both pathogens survived well in all salads, with a 0.2–1.6 log CFU/g reduction after 5 days (except for toum sauce with >3.5 log CFU/g reduction after 4 days). At 10°C, Salmonella in the different TC salads remained constant, whereas Shigella numbers significantly increased by 1.0–1.7 log CFU/g after 5 days. Yet, both pathogens significantly decreased by 1.2–1.4 log CFU/g in coleslaw after 5 days and by >3.5 log CFU/g in toum sauce after 3 days. At 24°C, Salmonella significantly increased in TC salad without additives by 1.4 log CFU/g after 5 days and were below the detection level in the other types of salad after 5 days. However, Shigella numbers significantly increased by 1.0 log CFU/g in TC with tahini, but they significantly declined by 1.9–2.9 log CFU/g in TC salads after 5 days, and the pathogen was not detected in coleslaw and toum sauce after 4 days.     

Health-promoting benefits of low-fat akawi cheese made by exopolysaccharide-producing probiotic Lactobacillus plantarum isolated from camel milk

Lactic acid bacteria isolated from camel milk exhibit remarkable probiotic and exopolysaccharide (EPS)-producing characteristics. The health-promoting benefits of exopolysaccharide-producing probiotic Lactobacillus plantarum isolated from camel milk used for making low-fat akawi cheese were investigated. Three low-fat akawi cheeses were made using traditional culture (non-EPS-producing, EPS^?), commercial EPS-producing (MEPS⁺), and camel milk EPS-producing (CEPS⁺) cultures. α-Amylase and α-glucosidase inhibitory activities, antioxidant activities, angiotensin-converting enzyme (ACE) inhibition, and antiproliferative activity were determined. Cheese made with CEPS⁺ culture exhibited comparable α-amylase inhibition to that of cheeses made with MEPS⁺. Scavenging rates of cheese made with EPS⁺ cultures were higher than those of cheese made with EPS^? cultures. The percentage of α-glucosidase inhibition ranged from >45% at 0 d to ～55% at 21 d of storage. After 7 d of storage, the scavenging rate in CEPS⁺ cheese increased >60% by ABTS assay [2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid)] and >20% by DPPH assay (1,1-diphenyl-2-picrylhydrazyl). Throughout storage, cheese made with EPS⁺ cultures showed higher ACE-inhibition activity compared with EPS^? cultures. Cheese made with CEPS⁺ showed ACE inhibition >70% after 7 d of storage. Antiproliferation activity of CEPS⁺ cheese increased from 38 to 48% during 7 d of storage and was maintained above 45% with prolonged storage. Low-fat akawi cheese produced with these cultures exhibited similar or greater health-promoting benefits compared with cheese made using commercial starter cultures. Therefore, incorporation of these cultures in food is promising for commercial uses.     

Recent Techniques for Harvesting Energy from the Human Body

The human body contains a near-infinite supply of energy in chemical, thermal, and mechanical forms. However, the majority of implantable and wearable devices are still operated by batteries, whose insufficient capacity and large size limit their lifespan and increase the risk of hazardous material leakage. Such energy can be used to exceed the battery power limits of implantable and wearable devices. Moreover, novel materials and fabrication methods can be used to create various medical therapies and life-enhancing technologies. This review paper focuses on energy-harvesting technologies used in medical and health applications, primarily power collectors from the human body. Current approaches to energy harvesting from the bodies of living subjects for self-powered electronics are summarized. Using the human body as an energy source encompasses numerous topics: thermoelectric generators, power harvesting by kinetic energy, cardiovascular energy harvesting, and blood pressure. The review considers various perspectives on future research, which can provide a new forum for advancing new technologies for the diagnosis, treatment, and prevention of diseases by integrating different energy harvesters with advanced electronics.     

Temperature-Sensitive Microcapsules Containing Lactoferrin and Their Action Against Carnobacterium viridans on Bologna

ABSTRACT:  Lactoferrin (LF) was encapsulated in 2 types of emulsion to protect it from contact with agents like divalent cations, which interfere with its antimicrobial activity. First, paste-like microcapsules were prepared as water-in-oil (W₁/O) emulsions from mixtures of 20% w/v LF in distilled water, 20% w/v LF in 3% w/v sodium lactate or in 20 mM sodium bicarbonate, which were emulsified with an oil mixture of 22% butter fat plus 78% corn oil and 0.1% polyglycerol polyricinoleate. Second, freeze-dried double emulsion (W₁/O/W₂), powdered microcapsules were produced following emulsification of paste-like microcapsules in an external aqueous phase (W₂) consisting of a denatured whey protein isolate (WPI) solution. The release of LF from the W₁/O microcapsules was dependent on temperature and NaCl concentration. LF was not released from the W₁/O emulsion at <5.5 °C. Its release was greater from W₁/O microcapsules when suspended in 5% aqueous NaCl than in water at ≥10 °C, whereas LF release from freeze-dried microcapsules was not controlled by temperature change. Paste-like microcapsules were incorporated in edible WPI packaging film to test the antimicrobial activity of LF against a meat spoilage organism Carnobacterium viridans . The film was applied to the surface of bologna after its inoculation with the organism and stored under vacuum at 4 or 10 °C for 28 d. The growth of C. viridans was delayed at both temperatures and microencapsulated LF had greater antimicrobial activity than when unencapsulated. The temperature-sensitive property of the W₁/O microcapsules was reduced when they were incorporated into a WPI film.     

Occurrence and Antimicrobial Susceptibility of Listeria monocytogenes Isolated from Brined White Cheese in Jordan

Listeria monocytogenes is a serious foodborne pathogen that has been isolated from different dairy food products. Several foodborne outbreaks of listeriosis have been associated with consumption of cheese. The aims of this study were to determine the occurrence of L. monocytogenes and Listeria spp. in brined white cheese (BWC) sold in Jordan, and to determine the susceptibility of isolated L. monocytogenes to antimicrobials. Three hundred and fifty samples of 5 different types of BWC (akkawi, boiled, halloumi, pasteurized, and shellal) were collected from a local market in Jordan. The ISO (11290-1) procedure was followed for isolation and identification of Listeria spp. from cheese samples and a polymerase chain reaction (PCR) technique was used for confirmation of L. monocytogenes isolates. The VITEK2 automated system was used for testing antimicrobial susceptibility of L. monocytogenes isolates. The overall prevalence of Listeria spp. in cheese sample was 27.1%. L. monocytogenes was isolated from 39 (11.1%) samples. Other isolated species were L. grayi (6.9%), L. innocua (2%), L. ivanovii (4%), L. seeligeri (2%), and L. welshimeri (0.3%). The pH values and salt concentrations of L. monocytogenes positive cheese samples ranged from 5.10 to 6.32 and 5.64 to 13.16, respectively. L. monocytogenes isolates were sensitive or intermediate susceptible to imipenem, gentamicin, linezolid, teicoplanin, vancomycin, fusidic acid, trimethoprim/sulfamethoxazole, benzylpenicillin, ciprofloxacin, erythromycin, tetracycline, and rifampicin, but resistant to fosfomycin, oxacillin, and clindamycin.     

Impact of environmental stress desiccation, acidity, alkalinity, heat or cold on antibiotic susceptibility of Cronobacter sakazakii

Cronobacter sakazakii is an emerging foodborne pathogen that has been implicated in severe forms of meningitis, septicemia or necrotizing colitis in pre-term neonates. Although illness outbreaks (primarily associated with powdered infant formula, PIF) caused by this pathogen are rare, the case-fatality rate may reach 50%. Successful treatment of C. sakazakii infection is reliant upon clinical use of antibiotics (AB) such as ampicillin. Recent reports showed increased resistance of C. sakazakii to broad-spectrum antibiotics. The objective of this study was to evaluate the effect of extreme pH (3.5 for 30 min or 11.25 for 5 min), cold (4 °C for 24 h), heat (55 °C for 5 min), and desiccation (cells were dried at 40 °C for 2 h and held at 21 °C for 4 d) stresses on susceptibility of five isolated strains of C. sakazakii to streptomycin, gentamicin, kanamycin, neomycin, tetracycline, doxycycline, tilmicosin, florfenicol, ampicillin, amoxicillin, vancomycin, ciprofloxacin and enrofloxacin. All unstressed strains of C. sakazakii were sensitive to streptomycin, gentamycin, kanamycin, ciprofloxacin, enrofloxacin, ampicillin and amoxicillin, but were moderately resistant or resistant to the rest. Exposing cells to alkaline or acidic stress did not change their sensitivity toward streptomycin, gentamycin, kanamycin or ciprofloxacin, but their resistance toward the other AB was increased. Cells stressed by desiccation showed increased sensitivity toward streptomycin, gentamicin, kanamycin, ciprofloxacin, enrofloxacin, ampicillin and doxycycline, but showed resistance toward the others. Cold-stressed cells were more sensitive to streptomycin, gentamicin, kanamycin, and ciprofloxacin compared with heat-stressed cells, but both heat and cold-stressed cells showed increased resistance toward all the other AB. Results obtained will help in understanding the effect of environmental stresses during processing on C. sakazakii susceptibility to AB.     

Detergent and sanitizer stresses decrease the thermal resistance of Enterobacter sakazakii in infant milk formula

ABSTRACT:  This study determined the effect of acid, alkaline, chlorine, and ethanol stresses on the thermal inactivation of Enterobacter sakazakii in infant milk formula. Unstressed or stressed cells were mixed with reconstituted powdered infant milk formula (PIMF) at temperatures between 52 and 58 °C for various time periods or mixed with PIMF prior to reconstitution with hot water between 50 and 100 °C. D - and z -values were determined using liner regression analysis. In general, detergent and sanitizer stresses decreased the thermal resistance of E. sakazakii in infant milk formula. The results of this study may be of use to regulatory agencies, manufacturers, and infant caregivers to design heating processes to eliminate E. sakazakii .