Gulsun Akdemir Evrendilek

Pulsed Electric Fields: Processing System, Microbial and Enzyme Inhibition, and Shelf Life Extension of Foods

Pulsed electric field (PEF) nonthermal food processing has been of growing interest owing to because of its excellent potential in providing consumers with microbiologically safe and fresh quality foods. Application of high-voltage electric fields at a certain level for a very short time by PEF not only inhibits pathogenic and spoilage microorganisms but also results in the retention of flavor, aroma, nutrients, and color of foods. This paper provides the most current information about PEF food processing. It reviews the systems for PEF processing and its effects on the inhibitions of microorganisms and enzymes and sensory and nutritional properties of foods. Regulatory issues of PEF processing are discussed as well

Inactivation of Penicillum expansum in sour cherry juice, peach and apricot nectars by pulsed electric fields

Inhibitory effects of pulsed electric fields (PEF) on Penicillum expansum inoculated into sour cherry juice, apricot and peach nectars were determined based on germination tube elongation, spore germination rate, and light and scanning electron microscopy (SEM) observations in this study. After inoculation of juice/nectar samples with P. expansum spores at the level of 10(5)-10(6)cfu/mL, the samples were processed by bench scale PEF pulse generator as a function of differing electric field strengths (0, 13, 17, 20, 23, 27, 30 and 34kV/cm) and processing times (0, 62, 94, 123, 163, 198 and 218mus). Results revealed that with an increase in electric field strength and processing time, germination tube elongation and spore germination rate were completely inhibited. Light and SEM observations revealed considerable morphological alterations in fungal conidia such as cytoplasmic coagulation, vacuolations, shrinkage and protoplast leakage. PEF processing of juice/nectars was demonstrated to be effective in inactivating P. expansum. To our knowledge, this is the first study confirming the inhibitory effects of PEF on germination tube elongation and spore germination rate of P. expansum in fruit juice/nectars.

Empirical prediction and validation of antibacterial inhibitory effects of various plant essential oils on common pathogenic bacteria.

In this study, fractional compound composition, antioxidant capacity, and phenolic substance content of 14 plant essential oils-anise (Pimpinella anisum), bay leaves (Laurus nobilis), cinnamon bark (Cinnamomum verum), clove (Eugenia caryophyllata), fennel (Foeniculum vulgare), hop (Humulus lupulus), Istanbul oregano (Origanum vulgare subsp. hirtum), Izmir oregano (Origanum onites), mint (Mentha piperita), myrtus (Myrtus communis), orange peel (Citrus sinensis), sage (Salvia officinalis), thyme (Thymbra spicata), and Turkish oregano (Origanum minutiflorum)--were related to inhibition of 10 bacteria through multiple linear or non-linear (M(N)LR) models-four Gram-positive bacteria of Listeria innocua, coagulase-negative staphylococci, Staphylococcus aureus, and Bacillus subtilis, and six Gram-negative bacteria of Yersinia enterocolitica, Salmonella Enteritidis, Salmonella Typhimurium, Proteus mirabilis, Escherichia coli O157:H7, and Klebsiella oxytoca. A total of 65 compounds with different antioxidant capacity, phenolic substance content and antibacterial properties were detected with 14 plant essential oils. The best-fit M(N)LR models indicated that relative to anise essential oil, the essential oils of oreganos, cinnamon, and thyme had consistently high inhibitory effects, while orange peel essential oil had consistently a low inhibitory effect. Regression analysis indicated that beta-bisabolene (Turkish and Istanbul oreganos), and terpinolene (thyme) were found to be the most inhibitory compounds regardless of the bacteria type tested.

Effect of Pulsed Electric Fields on Physical, Chemical, and Microbiological Properties of Formulated Carrot Juice

The objective of this study was to process a developed carrot juice-based beverage by pulsed electric fields (PEF) and determination of its physical, chemical, and microbiological properties before and after PEF processing. Results revealed that PEF processing did not cause any significant change in pH, titratable acidity (TA), °Brix, conductivity, color (L*, a*, and b*), nonenzymatic browning index (NBI), metal ion, and vitamin C concentration (p > 0.05). There was a significant reduction on the total aerobic mesophilic bacteria, total mold and yeast, total enterobactericeae and Escherichia coli O157:H7 counts resulting with 4.30 ± 0.26, 3.4 2 ± 0.40, 4.46 ± 0.36, and 3.57 ± 0.32 log cfu/mL, respectively (p ≤ 0.01). PEF processing could be successfully used to process a carrot juice based beverage with significant amount of microbial reduction.

Modelling stochastic variability and uncertainty in aroma active compounds of PEF-treated peach nectar as a function of physical and sensory properties, and treatment time

Effects of pulsed electric field (PEF) processing on 28 aroma active compounds, and four physical and eight sensory properties of peach nectar were explored using the best-fit multiple linear regression (MLR) models and Monte Carlo simulations as a function of the treatment times of 0, 66, 131, and 210 μs. The PEF treatment time of 131 μs on average led consistently to the least loss of most compounds. Significantly enhanced or no significant changes in the sensory properties were found as a function of the PEF treatment times. The most influential sensory predictor of the 28 MLR models was flavour, while the aroma compound most influential on the sensory properties of aftertaste, flavour, sweetness, and overall acceptance was octadecanoic acid. Monte Carlo simulations were used for the probabilistic assessments of stochastic variability and uncertainty associated with aroma active compounds of PEF-treated peach nectar.

Apricot Nectar Processing by Pulsed Electric Fields

Application of pulsed electric fields to process apricot nectar by determining the pH, °Brix, total acidity, conductivity, color, non-enzymatic browning index, concentration of mineral ions, and retention of ascorbic acid and beta carotene as well as inactivation of Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, Pseudomonas syringae subs. syringae, Erwinia carotowora, Penicillum expansum, and Botrytis cinerea was explored in this study. Processing of apricot nectar did not cause a significant difference in measured attributes (p > 0.05). However, inactivation of all microorganisms was significantly increased with increased electric field strength and treatment time (p ≤ 0.05). Microbial inactivation data fit both the Weibull distribution and log-logistic model.

Characterisation and fate of grayanatoxins in mad honey produced from Rhododendron ponticum nectar

Mad honey from Rhododendron ponticum nectar is produced in a large quantity in the western Black Sea region of Turkey and causes poisoning due to consumption of grayanatoxins (GTX I and III). There are a few studies about characterisation of GTXs in mad honey produced from R.ponticum. This study quantified basic properties including concentrations of GTX I and GTX III in mad honey samples collected in three consecutive years. Although the chemical composition of mad honey varied annually depending on the production year, mean GTX I and GTX III contents were estimated at 20.4±1.69 and 8.20±1.93mg/kg, respectively. The concentrations of GTXs did not change significantly during storage of 6months.

Histopathological effects of aloe barbadensis and soybean Oil on rat liver

Aloe Barbadensis, una especie de Aloe vera, es una planta popular usada por el comun de las personas y tambien en la medicina alternativa. El estudio tuvo como objetivo analizar los efectos del Aloe Barbadensis y aceite de soya en el higado. Para el estudio se emplearon ratas Wistar hembras Albino y se dividieron en 3 grupos: grupo control I sin tratamiento; grupo II A. barbadensis disuelta en aceite de soja (25 mg / dia), y grupo III tratado solo con aceite de soja (500 mg / dia). Fueron extraidas biopsias del lobulo derecho del higado de las ratas y luego se analizaron con microscopio de luz. En el grupo I el higado de las ratas era normal. En los grupos II y III, se observo aumento del tamano nuclear, leve aumento de la cromatina y degeneracion hidropica y binucleacion en algunos hepatocitos. La histologia hepatica mostro la congestion en las venas porta, sinusoides y las centrales. En el grupo III, la congestion venosa portal y en el Grupo II la congestion sinusoidal fue evidente. Ademas, el Grupo III revelo infiltracion de plasmocitos en areas portales. El uso de soja con Aloe Barbadensis es sinergista y aumenta cada uno de otros efectos. Infiltraciones mononucleares en el grupo III determinan la reaccion inflamatoria. Sin embargo, no observamos infiltracion mononuclear en el Grupo II, este mostro efectos antiinflamatorios de la Aloe Barbadensis. Esto determina que, dependiendo de la dosis usada de Aloe Barbadensis, los efectos toxicos pueden cambiar. Si es usado en altas dosis Aloe Barbadensis puede producir efectos toxicos en los hepatocitos.

Impacts of pulsed electric field and heat treatment on quality and sensory properties and microbial inactivation of pomegranate juice

Synergistic effects of pulsed electric field+mild heat on quality properties of pomegranate juice were modeled using the best-fit multiple (non-) linear regression models with inactivation kinetics parameters of Escherichia coli O157:H7 and Staphylococcus aureus. No significant difference was detected between the control and the treated samples in terms of pH; °Brix; total antioxidant capacity; total monomeric anthocyanin content; total ascorbic acid concentration; and the sensory properties of flavor, taste, aftertaste, and overall acceptance (p > 0.05). An exposure of 65.3 J and 40 ℃ caused an increase on conductivity; titratable acidity; L*, a*, and b* values; and a decrease of browning index, total phenolic content, total antioxidant capacity, total monomeric anthocyanin content, total ascorbic acid concentration, and in the sensory properties of color and sourness in pomegranate juice. The goodness-of-fit for the best-fit multiple (non-) linear regression models in descending order belonged to E. coli O157:H7 (92.98%), S. aureus (84.06%), color a* (83.9%), titratable acidity (81.3%), color L* (78.5%), color b* (78.3%), conductivity (74.8%), total phenolic content (74.1%), and total ascorbic acid concentration (64.74%), respectively. De and ze values for E. coli O157:H7 and S. aureus ranged from 105.64 to 1093.25 and from 79.18 to 1057.73 µs with 27.39 and 30.80 J, consequently.