Observation of injured E. coli population resulting from the application of high-pressure throttling treatments.

This study used flow cytometry (FC), epifluorescent microscopy (EM), and conventional culture media (PC) to evaluate the potential for high-pressure throttling (HPT) to produce injury in E. coli. E. coli cells suspended at a concentration of approximately 8 log (CFU/mL) in Butterfield's phosphate buffer and UHT skimmed milk, were treated with HPT at pressures ranging from 35 to 283 MPa. Cells were stained with SYTO 9 and propidium iodide (Live/Dead Baclight kit) to assess their membrane integrity. MacConkey and Tryptone Soy agars and a modification of the thin agar layer method were used to determine injured and non-injured cells. PC results indicated a reduction in E. coli counts as pressure increased but no significant injured population was detected in either matrix. However, FC and EM observations indicated that the membrane integrity of a portion of the bacterial population was affected by HPT, producing different degrees of cell injury that could be sublethal. The percentage of this heterogeneous population increased with applied pressure. These results reassert the importance of understanding the potential of new processing treatments to produce sublethally-injured bacteria, and developing appropriate detection techniques.

Microbial inactivation kinetics in soymilk during continuous flow high-pressure throttling.

The thermal resistance of Clostridium sporogenes PA 3679 ATCC 7955 was determined in soymilk (pH 7) and 0.1% peptone water (pH 7) by the capillary tube method. In the continuous flow high-pressure throttling, the temperature of soymilk increased due to instantaneous pressure release and the additional heat was supplied by a heat exchanger to achieve the set temperature. The soymilk was immediately cooled after a short preset hold time to below 40 degrees C. A significant increase in the heat resistance was observed in C. sporogenes spores when heated in soymilk in comparison to 0.1% peptone water. The D(121)-value for spores in soymilk was approximately 3-folds higher than peptone water. The z-value was also much higher in soymilk as compared to that in 0.1% peptone water. Continuous flow high-pressure throttling (HPT) from 207 or 276 MPa to atmospheric pressure reduced the microbial populations in inoculated soymilk up to 6 log cycles when the holding times were 10.4, 15.6, and 20.8 s and the process temperatures were 85, 121, 133, and 145 degrees C, respectively. The sporicidal effect increased as the operating pressure, time, and temperature were increased. More injured spores were found at 207 MPa than at 276 MPa, indicating that lower pressure caused cell injury whereas high pressure caused cell death.

Supercritical fluid extraction of limonoid glucosides from grapefruit molasses.

Limonoid glucosides (primarily limonin 17-beta-D-glucopyranoside, LG) were extracted from grapefruit molasses by supercritical fluid extraction using a supercritical carbon dioxide-ethanol (SC CO(2)-ethanol) system. Extraction conditions to maximize the yield of LG were determined by varying pressure, temperature, ethanol concentration, and extraction time. The highest yield of LG at 0.61 mg/g molasses was obtained at a pressure 48.3 MPa, a temperature of 50 degrees C, 10% ethanol (X(Eth) = 0.1), and 40 min of extraction time at a flow rate of 5.0 L/min. The results demonstrated that SC CO(2) extraction of limonoid glucosides from grapefruit molasses has practical significance for commercial production.

Major flavonoids in grape seeds and skins: antioxidant capacity of catechin, epicatechin, and gallic acid.

Grape seeds and skins are good sources of phytochemicals such as gallic acid, catechin, and epicatechin and are suitable raw materials for the production of antioxidative dietary supplements. The differences in levels of the major monomeric flavanols and phenolic acids in seeds and skins from grapes of Vitis vinifera varieties Merlot and Chardonnay and in seeds from grapes of Vitis rotundifolia variety Muscadine were determined, and the antioxidant activities of these components were assessed. The contribution of the major monomeric flavonols and phenolic acid to the total antioxidant capacity of grape seeds and skins was also determined. Gallic acid, monomeric catechin, and epicatechin concentrations were 99, 12, and 96 mg/100 g of dry matter (dm) in Muscadine seeds, 15, 358, and 421 mg/100 g of dm in Chardonnay seeds, and 10, 127, and 115 mg/100 g of dm in Merlot seeds, respectively. Concentrations of these three compounds were lower in winery byproduct grape skins than in seeds. These three major phenolic constituents of grape seeds contributed <26% to the antioxidant capacity measured as ORAC on the basis of the corrected concentrations of gallic acid, catechin, and epicatechin in grape byproducts. Peroxyl radical scavenging activities of phenolics present in grape seeds or skins in decreasing order were resveratrol > catechin > epicatechin = gallocatechin > gallic acid = ellagic acid. The results indicated that dimeric, trimeric, oligomeric, or polymeric procyanidins account for most of the superior antioxidant capacity of grape seeds.

Microbiological Examination of Pasteurized, Deaerated Human Milk.

Three composites of human milk samples were subjected to different processing conditions: (1) deaerated, vacuum packaged in metalized polyester bags and pasteurized at 56°C for 8 min; (2) vacuum packaged and pasteurized; (3) vacuum packaged. On days 0, 4, 7, 14, 28, 64, and 96 of storage, each treatment was analyzed for dissolved oxygen content and viable microflora. On days 0, 4, and 14, randomly selected isolates from each treatment were identified to the species level. Heat treatment of the milk samples reduced the number of viable microorganisms and resulted in a shift in the type of bacteria in the milk. Pasteurized samples contained primarily non-pathogenic skin commensals, while non-pasteurized samples were populated by species of Pseudomonas and other Gram negative microorganisms, including potential pathogens. Deaeration did not affect either the number or types of microorganisms surviving the heat treatment.

Thermal Destruction of Escherichia coli and Klebsiella pneumoniae in Human Milk.

A continuous flow high-temperature short-time pasteurization system was used to determine kinetic parameters (D- and z-values) for thermal destruction of the bacterial pathogens, Escherichia coli and Klebsiella pneumoniae , in mature human milk. D-and z-alues of each bacterium were determined from data on survivors enumerated on both selective media, Violet Red Bile agar or MacConkey's, and on a non-selective medium, nutrient agar (NA). For E. coli , D-values were determined at 58, 60, 62 and 64°C. The predicted value of D at 60°C is 31.5 s. The z-value for E. coli is 3.2°C. D-values for K. pneumoniae were determined at 52, 56 and 58°C. Based on these data the predicted value of D at 60°C is 1.3 s. The z-value for K. pneumoniae , is 2.8°C. For both E. coli and K. pneumoniae , counts on NA tend to be higher than on selective media. This is undoubtedly due to the inhibitory nature of the selective media. This also suggests that some degree of thermal injury may occur for each organism.

Thermal Destruction of Staphylococcus aureus in Human Milk.

Rates of thermal destruction of Staphylococcus aureus were determined in mature human milk using a continuous flow high-temperature short-time pasteurization system. D and z values for inactiviation of S. aureus were determined from data on survivors capable of forming colonies in an appropriate selective medium. The effects of thermal injury on D and z values were assessed by survivor colony forming units (CFU) on Staphylococcus medium 110 (SMI 10), nutrient agar (NA), Trypticase Soy Agar (TSA), Trypticase Soy Agar with 7.5% NaCi (TSAS) and Baird-Parker medium (BP) (Difco Laboratories, Detroit, MI). D values for inactivation of S. aureus at 52, 58 and 60 and 62°C were used to predict D at 60°C of 15.3 s and 24.3 s when based on survivor CFU in SM 110 and nutrient agar, respectively. The z value was 4.9°C in either medium. D-values for inactivation of S. aureus at 60, 62, 64 and 67°C were used to predict D at 60°C of 41.2 s, 41.0 s and 34.7 s when based on survivor CFU in BP, TSA and TSAS, respectively. The z values were 6.5, 6.5 and 6.4°C, respectively.

IgA, IgG, IgM and Lactoferrin Contents of Human Milk During Early Lactation and the Effect of Processing and Storage.

The total IgA, IgG, IgM and lactoferrin concentrations in human milk from 89 donors were studied at three lactational stages: early transitional (3 to 8 d postpartum), transitional (10 to 14 d postpartum) and mature (30 to 47 d postpartum). The effects of processing and storage on these components in composite samples of mature human milk were determined. There were no significant diurnal variations in any of the four protective factors at either the transitional or mature stages. Concentrations of total IgA, IgM and lactoferrin decreased significantly as time postpartum increased, whereas the IgG content showed no significant changes. The total IgA, IgM and lactoferrin levels were significantly decreased by all heat treatments (62.5°C for 30 min, 72°C for 15 s, 88°C for 5 s, and 100°C for 5 min). Heating at 62.5°C for 30 min did not affect the IgG content; however, the other heat treatments significantly reduced IgG concentration. At the times and temperatures selected for this study, the two lower temperature treatments were less detrimental to the protective factors than the higher temperature treatments.