D VALUES OF COMPOSITE SALMONELLA ENTERICA SEROTYPES TYPHIMURIUM AND ENTERITIDIS IN PHILIPPINE NATIVE ORANGE JUICE

ABSTRACT

This study established the decimal reduction times (D values) of a composite inoculum of Salmonella enterica serotypes Typhimurium (American Type Culture Collection 13311 and E 1366) and Enteritidis (BIOTECH 1963) in Philippine native orange juice (pH 3.0, 0.84 % citric acid, 8.4°Brix). Acid‐adapted cells (10 log₁₀ cfu/g) were heated to 50–70C for 0–1.5 min and recovered by surface plating onto a selective (bismuth sulfite agar) and a nonselective medium (nutrient agar [NA]). Results showed that in both enumerating media and in all heating temperatures, survivor populations significantly decreased (P < 0.05) with increasing treatment time. The greater populations enumerated on NA in all treatment times were attributed to the sublethal injuries imparted by the acidity of the suspending medium and the heat treatments. The D values calculated from the survivor populations on both media were not significantly different (P > 0.05). The D values ranged from 0.16 to 0.40 min.

PRACTICAL APPLICATIONS

This study established the thermal inactivation rates of a composite Salmonella spp. inoculum in a Philippine orange juice medium. Salmonella is a target organism pertinent in the assuring citrus juices. Hence, appropriate thermal process schedules for citrus juices with similar physicochemical properties as the test medium, against the test organisms may be calculated using the results obtained from this study.

     

Pasteurization of Apple Juice Contaminated with Escherichia coli by a Combined UV–Mild Temperature Treatment

The bactericidal efficacy of ultraviolet (UV) treatments to fruit juices is limited because of their low UV transmittance; therefore, it is necessary to design combined processes to improve their lethality. This investigation was carried out to determinate the lethal effect of UV-C treatments at mild temperatures (UV-H treatments) on the UV-resistant Escherichia coli strain Spanish Type Culture Collection (STCC) 4201 suspended in apple juice. A synergistic effect was observed and the optimum temperature for the combined process was established. Subsequently, the effect of the optimized treatment on the lethality of an E. coli cocktail (STCC 4201, STCC 471, American Type Culture Collection (ATCC) 27325, ATCC 25922, and O157:H7 Chapman strain) and on freshly squeezed apple juice quality was evaluated. A UV treatment of 20.33 J/mL reached 0.61?±?0.01, 0.83?±?0.07, 1.38?±?0.04, 1.97?±?0.06, 3.72?±?0.14, 5.67?±?0.61, and more than 6 log₁₀ cycles of inactivation at 25.0, 40.0, 50.0, 52.5, 55.0, 57.5, and 60.0 °C, respectively. The optimum conditions for exploiting the synergistic effects were UV doses of 27.10 J/mL, temperature of 55.0 °C, and 3.58 min of treatment time. This treatment guaranteed more of 5 log₁₀ reductions of the cocktail of five strains of E. coli without affecting pH, °Brix, and acidity of freshly squeezed apple juice. The UV-H treatment did not increase the loss of ascorbic acid compared to the same UV treatment at room temperature but approximately doubled the inactivation of polifenoloxidase.     

In vitro inhibition of Escherichia coli O157:H7 by bifidobacterial strains of human origin

The ability of bifidobacteria isolated from infant feces to inhibit enterohemorrhagic Escherichia coli serotype O157:H7 in vitro and reduce its adhesion to human enterocyte-like Caco-2 cells was evaluated in comparison to American Type Culture Collection bifidobacterial reference strains. Five Bifidobacterium isolates from infant feces were identified and characterized by morphology, fructose-6-phosphate phosphoketolase (F6PPK) assay, polymerase chain reaction using bifidobacterial 16S rDNA specific primers, carbohydrate fermentation patterns, resistance to lysozyme, acid, bile and hydrogen peroxide as well as their ability to inhibit E. coli O157:H7 using the agar spot technique. Infant isolates showed greater resistance to bile, acid, lysozyme and more antimicrobial activity against E. coli O157:H7 than ATCC strains. Two infant isolates identified as B. bifidum RBL 71 and B. bifidum RBL 460 showed good adhesion and significant potential for reducing adhesion of E. coli O157:H7 to Caco-2 cells. This effect was dependent on bifidobacterial cell concentration. These results show that bifidobacteria isolated from infants may be useful for improving probiotic formulae with respect to protection against E. coli O157:H7 infection.     

沙门氏菌选择性化学限定培养基的研制

目的 拟用氨基酸、维生素、无机盐替代牛肉膏和蛋白胨,开发质量可控的化学限定沙门氏菌选择性培养基.方法 分别研究20种氨基酸、11种维生素或4种无机盐对大肠杆菌ATCC 25922生长特性的影响,并确定生长最适浓度,替换亚硫酸铋(BS)琼脂或Hektoen Enteric(HE)琼脂中的牛肉膏和蛋白胨,研制出化学限定BS...     

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.     

Impact of different pasteurization temperatures on the survival of microbial contaminants isolated from pasteurized milk

The thermal inactivation of selected microbes was studied using the low temperature long time (LTLT), high temperature short time (HTST) and 'pot' pasteurization methods. Survivors were enumerated after heating for up to 40 min for the LTLT and HTST pasteurization methods and after heating for up to 30 min for the 'pot' pasteurization method. With the exception of the Bacillus cereus strain, the selected microbes did not survive the LTLT and HTST pasteurization methods. The results from the 'pot' pasteurizer showed that B. cereus, Chryseobacterium meningosepticum, Pseudomonas putida, Acinetobacter baumannii and Escherichia coli strains survived the pasteurization conditions applied, showing that the 'pot' pasteurizer does not pasteurize effectively.     

Thermal inactivation of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in breaded pork patties

ABSTRACT:  Decimal reduction times ( D -values) and thermal resistance constants ( z -values) for 3 foodborne pathogenic bacteria in formulated ready-to-eat breaded pork patties were determined with thermal inactivation studies. Meat samples, inoculated with Escherichia coli O157:H7, Salmonella , and Listeria monocytogenes cultures or uninoculated controls, were packaged in sterile bags, immersed in circulated water bath, and held at 55, 57.5, 60, 62.5, 65, 67.5, and 70 °C for different durations of time. The D - and z -values were determined by using a linear regression model. Average calculated D -values for E. coli O157:H7, Salmonella , and L . monocytogenes at a temperature range of 55 to 70 °C were 32.11 to 0.08 min, 69.48 to 0.29 min, and 150.46 to 0.43 min, respectively. Calculated z -values for E. coli O157:H7, Salmonella , and L. monocytogenes were 5.4, 6.2, and 5.9 °C, respectively. The results of this study will be useful to food processors to validate thermal lethality of the studied foodborne pathogens in ready-to-eat breaded pork patties.     

Storage stability of a stimulant coconut water–acerola fruit juice beverage

The objective of this work was to study the stability of a beverage formulated with acerola fruit juice and green coconut water with added caffeine. The beverage was prepared with 25% acerola pulp, 75% green coconut water and sugar up to 12°Brix, and caffeine (125 mg L⁻¹), heat processed at 90 °C for 30 s and packed in 250-mL glass bottles. Chemical, physicochemical, microbiological and sensory analyses of the beverage were performed just after processing and during 6 months of storage at room temperature (27 °C). The vitamin C content decreased significantly throughout storage, from 399.5 to 189.6 mg 100 mL⁻¹, although it has remained relatively high. The anthocyanins initially present (0.025 mg 100 mL⁻¹) were completely lost during the storage at a mean rate of 4 μg 100 mL⁻¹ month⁻¹. The product was microbiologically stable during storage. Colour changes were also observed with absorbance at 420 nm, with average values ranging from 0.19 to 0.24. However, according to the sensory analyses the product was acceptable during the 6 months of storage, presenting sensory scores (colour, taste and global acceptance) from 6.5 to 5.5, which suggests its potential for market.     

SURVIVAL AND GROWTH OF ACID ADAPTED ESCHERICHIA COLI STRAINS IN BROTH AT DIFFERENT PH LEVELS

Acid resistance of Escherichia coli O157:H7 strain UT 10 and Escherichia coli ATCC 25922 was determined in brain heart infusion broth at pH 7.4, 4.5 and 2.5. Variations due to acid stress in the counts of both strains were also determined. Acid adaptation enhanced the survival of both strains at pH 4.5, but neither strain could survive after 4 h at pH 2.5. At optimum growth conditions (pH 7.4), E. coli ATCC 25922 exhibited increased viability over E. coli UT 10. At pH 4.5, E. coli UT 10 was more tolerant to low pH than E. coli ATCC 25922. An increase in saturated fatty acids of both AA strains was observed, indicating the importance of lipid modification in enhancing survival at low pH. The results of this study indicated that the food industry should therefore adapt their processing/preservation procedures by taking the most acid tolerant pathogenic E. coli strains into consideration in order to ensure the safety of their products.

PRACTICAL APPLICATIONS

The study will enlighten the industry on the survival of acid adapted pathogens such as E. coli O157:H7 at low pH. It also indicates that current measures used in the preservation of low pH foods can trigger acid adaptation. For this reason, the effectiveness of current preservation measures in controlling foodborne pathogens should be reassessed. The importance of using cells adapted to different pH values in food challenge studies is also highlighted. Since fermented foods, which are generally regarded as safe, have been implicated in foodborne disease outbreaks, more attention should be given to the prevention of contamination of foods with pathogens such as E. coli O157:H7 since they may survive in low pH foods and cause disease.     

Inactivation of Escherichia coli JM109, DH5alpha, and O157:H7 suspended in Butterfield's Phosphate Buffer by gamma irradiation

ABSTRACT:  Food irradiation is a safe and effective method for inactivation of pathogenic bacteria, including Escherichia coli O157:H7, in meat, leafy greens, and complex ready-to-eat foods without affecting food product quality. Determining the radiation dose needed to inactivate E. coli O157:H7 in foods and the validation of new irradiation technologies are often performed through inoculation of model systems or food products with cocktails of the target bacterium, or use of single well-characterized isolates. In this study, the radiation resistance of 4 E. coli strains, 2 DNA repair deficient strains used for cloning and recombinant DNA technology (JM109 and DH5α) and 2 strains of serotype O157:H7 (C9490 and ATCC 35150), were determined. The D -10 values for C9490, ATCC 35150, JM109, and DH5α stationary phase cells suspended in Butterfield's Phosphate Buffer and irradiated at 4 °C were 229 (± 9.00), 257 (± 7.00), 61.2 (± 10.4), and 51.2 (± 8.82) Gy, respectively. The results of this study indicate that the extreme radiation sensitivity of JM109 and DH5α makes them unsuitable for use as surrogate microorganisms for pathogenic E. coli in the field of food irradiation research. Use of E. coli JM109 and DH5α, which carry mutations of the recA and gyrA genes required for efficient DNA repair and replication, is not appropriate for determination of radiation inactivation kinetics and validation of radiation processing equipment.     

餐饮食品中6病原菌叠氮丙啶-定量聚合酶链反应检测方法开发与检验数据分析

目的建立叠氮丙啶-定量聚合酶链反应法(propidiummonoazide-quantitativepolymerasechain reaction,PMA-qPCR)快速检测餐饮食品中6病原菌的方法。方法开发6种病原菌前增菌通用型培养基,采用热裂解方法提取样品DNA,采用PMA技术鉴别活菌与死菌,运用分子生物学技术检测样品中目标菌的特异性基因片段,建立病原菌的PMA-qPCR检测方法,开展餐饮食品样品病原菌筛查检测。结果本方法特异性良好,灵敏度较高, 1533份餐饮食品样品中检出病原菌71株,检出率为4.63%(71/1533)。结论本研究运用PMA-qPCR开展病原菌活菌检测技术研究,所建立研究方法可广泛应用于餐饮食品及相关食品中病原菌的快速筛查检测,具有较好的应用前景和现实意义。     

PREDICTIVE MODEL FOR THE COMBINED EFFECT OF TEMPERATURE,pH, SODIUM CHLORIDE,AND SODIUM PYROPHOSPHATE ON THE HEAT RESISTANCE OF ESCHERICHIA COLI O157:H71

The effects and interactions of heating temperature (5–62.5C), pH (4 – 8), NaCl (0 – 6%, w/v), and sodium pyrophosphate (0 – 0.3%, w/v) on the heat resistance of a four strain mixture of Escherichia coli O157:H7 in beef gravy were examined. Thermal death times were determined using a submerged coil heating apparatus. The recovery medium was plate count agar supplemented with 1% sodium pyruvate. Decimal reduction times (D-values) were calculated by fitting a survival model to the data with a curve fitting program. The D-values were analyzed by second order response surface regression for temperature, pH, NaCl and sodium pyrophosphate levels. The four variables interacted to affect the inactivation of the pathogen. Thermal resistance of E. coli O157:H7 can be lowered by combining these intrinsic factors. A mathematical model describing the combined effect of temperature, pH, NaCl and sodium pyrophosphate levels on the thermal inactivation of E. coli O157:H7 was developed. The model can predict D-values for any combinations of temperature, pH, NaCl and sodium pyrophosphate that are within the range of those tested.     

INVESTIGATION OF SHELF LIFE AND HEAT PENETRATION ATTRIBUTES OF READY-TO-EAT "FISH PEERA" FROM ANCHOVY (STOLEPHOROUS COMMERSONI) IN RETORT POUCHES

Fish peera, a traditional product from anchovies, was prepared and processed at 121.1C for 38 min in an over pressure autoclave in indigenously developed retort pouches having a three-layer configuration of 12.5 µm polyester/12.5 µm aluminum foil/80 µm cast polypropylene of size 11 cm  ×  17 cm. Heat penetration characteristics of the product were studied using Ellab CTF 9008 (Ellab A/S, Roedovre, Denmark), Fo cum cook value integrator. Fish peera was processed to a Fo value of 7 and cook value of 66.02 min. Storage studies with reference to sensory, biochemical and microbiological parameters indicated that the product had a shelf life of 1 year when stored at ambient temperature (28  ±  2C).

PRACTICAL APPLICATIONS

The demand for ready-to-eat fish products is increasing both in domestic and international market because of health benefits associated with fish and fishery products. Fish products thermally processed in retortable pouches offer several advantages. Apart from being less expensive, these products can be stored at ambient temperature for more than 12 months without any refrigeration. Many varieties of fish products, especially traditional and ethnic products are having great demand. Fish peera, a traditional dish of Kerala prepared using anchovies, have limited storage life at room temperature as the product becomes rancid due to coconut. This products can be kept for a period of 1 year at ambient temperature (28 ± 2C) when subjected to thermal processing at 121.1C for 38 min to a Fo value of 7 and cook value of 66 min in an over pressure autoclave in indigenously developed retort pouch.     

DEVELOPMENT OF A BLENDED NONALCOHOLIC BEVERAGE COMPOSED OF COCONUT WATER AND CASHEW APPLE JUICE CONTAINING CAFFEINE

ABSTRACT

In this work, the stability of a blended beverage composed by coconut water and clarified cashew apple juice (“cajuina”) is presented. The physicochemical, microbiological and sensory stability of a blended nonalcoholic beverage composed of coconut water and cajuina (80:20 v/v) were evaluated during 6 months. The results showed that the beverage presented good stability in all analyzed parameters except for vitamin C, which presented a loss of about 80% of the initial content. The beverage color also presented changes during the storage time. Despite these alterations, the product acceptance during the storage period did not show any rejection.

PRACTICAL APPLICATIONS

The development of blended beverages is a good way of improving the nutritional quality of traditional products. By mixing two or more kinds of fruits, a product with more vitamins and minerals and with different sensory and flavor characteristics when compared to the raw materials is obtained. In the present work, coconut water and cashew apple juice were mixed to obtain a different product combining the nutritional components from both fruits. The blended beverage combines the high vitamin C content of the cashew apple juice with the high mineral level of the coconut water. Caffeine was also added conferring stimulating properties to the product. The product acceptance was evaluated by sensory analysis and presented good acceptance until 6 months of storage at room temperature, presenting the required characteristics for a commercial product.

     

SEASONAL VARIATIONS IN FATTY ACID COMPOSITION OF OIL IN DEVELOPING COCONUT

ABSTRACT

Studies on seasonal variation in oil and fatty acid profile of developing solid endosperm of two cultivars, West Coast Tall (WCT) and Chowghat Orange Dwarf (COD), and their hybrids indicated that oil percentage increased from 30% in 6‐month‐old nuts to 63% in matured nuts (12 months old). Nuts sampled during July from different levels of maturity had high oil percentage and followed by those sampled during April, October and January. During nut development to maturity, the percentages and contents of medium and long chain saturated fatty acids increased except that of palmitic and myristic acids. Concentration of long chain unsaturated fatty acids (LCUFAs) in developing coconut kernel were high at 5 and 6 months after fertilization and then decreased toward maturity. The LCUFAs were high in nuts developing during October; consequently, saturated to unsaturated fatty acid ratios were low during October. Results indicated that nuts matured during October had better nutritional quality for human consumption and those matured during January are more suitable for industrial purpose due to higher medium chain fatty acid concentrations.

PRACTICAL APPLICATIONS

Coconut is consumed either as the tender nut (5–6 months after fertilization) or as the kernel from mature nut (12 months after fertilization). Recent technologies of making snowball tender nut use the nuts aged 7–8 months old. Kernel also is consumed in this product. Apart from this, the coconut is being increasingly used for making different kernel‐based value‐added products. This information is useful, as the value‐added products are being developed using different maturities of coconut. Hence, it is of paramount importance that the fatty acid profile of coconut kernel is known in detail for assessing the safety of food consumption from the human health point of view. Apart from this, information on the seasonal variation in fatty acid profile of developing endosperm gives an integrated knowledge so as to optimize the usage of coconut kernel for both human consumption and industrial exploitation.

     

In Situ Bioconversion of Coconut Oil via Coconut Solid State Fermentation by Geotrichum candidum ATCC 34614

Coconut base solid state fermentation was carried out by Geotrichum candidum ATCC 34614 for in situ coconut oil bioconversion. Coconut oil, which contains highly saturated medium chain triglycerides, was partially bioconverted into a combination of medium chain diglycerides, medium chain monoglycerides and medium chain fatty acids by this fungus lipolytic activity. The product demonstrated improved aroma, flavor, thermal behavior and antibacterial activity. Maximum triglycerides conversion (76.5 %) occurred at 40 % moisture content and 50 % oil content after 25 days of incubation. Bioconverted coconut oil revealed as much as 95 % antibacterial activity as well as altered thermal characteristic towards lower melting and higher crystallization points. The fermented culture also revealed highly fruity and flora notes which contained five main short- and medium-chain esters known as aromatic compounds. The present study established the possibility of using G. candidum ATCC 34614 in coconut solid culture for bioconversion of coconut oil, which improves the fermented product characteristics.     

Thermal inactivation of Escherichia coli O157:H7 in ground beef supplemented with sodium lactate

A study was conducted to investigate the antimicrobial effect of sodium lactate (NaL) (0, 1.5, 3.0, and 4.5%) on the survival of Escherichia coli O157:H7 in 93% lean ground beef. Samples inoculated with a mixture of four strains of E. coli O157:H7 (10(7) to 10(8) CFU/g) were subjected to immersion heating in a water bath stabilized at 55, 57.5, 60, 62.5, or 65 degrees C. Results of statistical analysis indicated that the heating temperature was the only factor affecting the decimal reduction times (D-values) of E. coli O157:H7 in 93% lean ground beef. The change in temperature required to change the D-value (the z-value) was determined as 7.6 degrees C. The thermal resistance of this organism was neither affected by the addition of NaL nor by the interactions between NaL and temperature. Adding NaL to ground beef to reduce the thermal resistance of E. coli O157:H7 is therefore not recommended.     

Decimal reduction times of Salmonella Typhimurium in guinataang kuhol: An indigenous Filipino dish

This study established the thermal inactivation of Salmonella Typhimurium (E1366) in a mixture of golden apple snail (Pomacea conaliculata Linn.) meat and coconut cream medium—a dish native to the Philippines locally known as guinataang kuhol. Artificially inoculated S. Typhimurium were heated to 60, 75 and 90 °C for 0-1.5 min. Survivor cells were enumerated using a selective and a nonselective enumerating medium, bismuth sulphite agar (BSA) and nutrient agar (NA), respectively. The thermal inactivation rates of Salmonella Typhimurium were expressed in terms of decimal reduction times (D-values). Results showed that in both enumerating media and in all heating temperatures, the number of surviving cells significantly (P<0.05) decreased with increasing treatment times. Survivor cell populations enumerated on NA were always significantly greater than those enumerated on BSA. The D-values calculated from the survivor counts on both media were however not significantly different. The calculated D-values ranged from 0.22 to 0.48 min.     

Comparison of the sensitivity of commercial strains and infant isolates of bifidobacteria to antibiotics and bacteriocins

Eighteen bifidobacteria, six isolated from infant feces and 12 commercial strains (of which 10 were purchased from the American Type Culture Collection), were tested for sensitivity to 14 antibiotics and four bacteriocins including nisin A, nisin Z, pediocin PA-1 and mutacin B-Ny266. All bacteria were resistant to vancomycin, kanamycin, neomycin and streptomycin. Infant isolates were more sensitive than commercial strains to cloxacillin, ampicillin, chloramphenicol, tetracycline, rifampicin and novobiocin. Sensitivity to bacteriocins determined by a microplate assay varied widely. Generally, nisin A was the most effective bacteriocin followed by nisin Z and mutacin B-Ny266. Pediocin PA-1 appeared to have no inhibition at 70 μg mL⁻¹. Commercial strains showed relatively variable sensitivity to bacteriocins compared to infant isolates, which were inhibited within a narrow range of bacteriocin concentration. Bacteriocin tolerance could be easily gained by prolonging the exposure time. Death–time curves and transmission electron microscopy (TEM) of logarithmic and stationary cells of two strains (Bifidobacterium adolescentis ATCC 15704 and infant isolate Bifidobacterium sp. RBL67) incubated with twice the minimum inhibitory concentration of nisin A and nisin Z for 3 h revealed that log-phase cells were more sensitive than stationary-phase cells. TEM showed that the cell membrane is the most likely site of bactericidal effects of nisin.