Effects of gamma irradiation on the microbiological,nutritional, and sensory properties of fresh vegetable juice

The radiation pasteurization process was performed to improve the microbiological quality of fresh vegetable juice. Carrot and kale juice were irradiated and their microbiological, nutritional, and sensory properties were evaluated. The contaminating bacteria in the juices before irradiation ranged from 10⁶ to 10⁷ CFU/ml. All the aerobic and coliform bacteria in the carrot juice were eliminated by irradiation at a dose of 3 kGy, whereas about 10² CFU/ml of the bacteria survived in the kale juice irradiated at up to 5 kGy. However, the cells that survived from irradiation in the kale juice did not grow, whereas those of the non-irradiated samples reached 10⁹ CFU/ml after 3 days of storage at 10 °C. Amino acids were stable at up to 5 kGy of an irradiation. Radiation resulted in a dose-dependent reduction of the ascorbic acid content. However, the contents of the total ascorbic acid, including dehydroascorbic acid, were stable at up to 3 kGy of an irradiation. The sensory evaluation results immediately after irradiation were not different in any of the samples. At a 3-day storage, the sensory quality of the irradiated juice was adequate, while the quality of the non-irradiated control was deteriorated.     

Inactivation of a non-pathogenic strain of E. coli by ionising radiation

Ionising radiation is an effective method to reduce pathogenic E. coli O157:H7 in meat and poultry products. Radiation sensitivity of bacteria, however, depends on several factors. After applying an irradiation dose of 1 kGy to cultures of the non-pathogenic strain of E. coli, DSM 498, grown and irradiated in nutrient broth, reductions of 3–4 decimal units were achieved (D₁₀ = 0.27 kGy). If grown on minced turkey meat, however, reduction rates were lower (D₁₀ = 0.47 kGy). Even lower reduction rates were obtained during irradiation of frozen meat (D₁₀ = 0.72 kGy) compared to treatments at cooling temperatures (D₁₀ = 0.48 kGy). For data evaluation, both, first order reduction kinetics and the Weibull model were compared. The results emphasise the necessity to determine inactivation kinetics in food matrices of target extrinsic factors (e.g. temperature).     

Effect of a pectin-based edible coating containing green tea powder on the quality of irradiated pork patty

Physicochemical, microbiological and sensorial qualities of cooked pork patty coated with pectin-based material containing green tea leaf extract powder were studied. Cooked pork patties were separated into three groups; uncoated control (C), coated with pectin-based materials (CP), and coated with pectin-based materials containing 0.5% green tea powder (CGP). The prepared patties were irradiated at 0 and 3 kGy using cobalt-60 gamma rays. Lipid oxidation, free radical scavenging effects, moisture content, total plate count, and sensory properties were evaluated during storage for 14 days at 10 °C. Lipid oxidation decreased (p ⩽ 0.05) and radical scavenging (p ⩽ 0.05) increased in the pork patties in CGP or CP relative to those of the controls when vacuum packaged. Coated patties contained higher moisture contents than the controls in both air- and vacuum packagings. The numbers of total aerobic bacteria were significantly reduced by the coating treatments as well as by irradiation. No difference were detected in sensory characteristics due to gamma irradiation or coating treatments.     

Hurdle effect of vinegar and sake on Korean seasoned beef preserved by sous vide packaging

A Korean beef product seasoned in concentrated soy sauce was vacuum packaged in a gas barrier plastic pouch and pasteurised. Adding vinegar and/or sake to the product was examined as preservation hurdles to improve microbial stability, and sensory quality affected by the additions was evaluated. A combination of vinegar and sake improved the microbial stability of the product at 8 and 20 °C, while added vinegar and/or sake did not improve the sensory quality of the product. The vinegar and sake combination produced significantly inferior initial quality in taste and overall acceptability. The sensory quality of the products with or without single use of vinegar or sake degraded significantly during 10 days of storage at 8 °C, which made the treatment effect less pronounced. Thus, the combined addition of vinegar and sake may be an alternative means of extending shelf life, because sensory quality with this treatment became close to that of the control after extended storage.     

Pentocin 31-1, a novel meat-borne bacteriocin and its application as biopreservative in chill-stored tray-packaged pork meat

Pentocin 31-1 was produced by Lactobacillus pentosus 31-1, isolated from the traditional China fermented Xuan-Wei Ham. In this work, study on its application as biopreservative in chill-stored nonvacuum-tray-packaged pork meat was carried out. Pentocin 31-1 was prepared by pH-adsorption in 5 l stainless steel fermentor. Each 200 ml semi-purified bacteriocin was obtained from one fermentation, and the specific activity was 1280 AU/ml. The effects of pentocin 31-1 on microbiological counts, physicochemical change and sensory quality of chilled pork in the period of preservation at 4 °C was investigated. Results showed that pentocin 31-1 could substantially inhibit the accumulation of VBN and generally suppress the growth of microflora, especially Listeria and Pseudomonas, during chilled pork storage. Microbiological counts, physicochemical parameters and sensory characteristics of the treatments (40 AU/ml pentocin 31-1 or 75 AU/ml nisin) had exceeded the limitation of Chinese hygienic standard for fresh meat of livestock by day 15. 80 AU/ml pentocin could extend the shelf life to 15 days and the meat showed good sensory characteristics. These results suggest the potential of pentocin 31-1 as a biopreservative in tray-packaged chilled pork storage.     

The effect of high pressure on microbial population,meat quality and sensory characteristics of chicken breast fillet

High hydrostatic pressure (300, 450 and 600 MPa) was used to investigate its effect on microbial population, meat quality and sensory characteristics of chicken breast fillets. Pressures of 450 and 600 MPa almost completely eliminated all the 3 major pathogens Salmonella typhimurium (KCTC 1925), Escherichia coli (KCTC 1682), and Listeria monocytogenes (KCTC 3569) and therefore improved safety of chicken breast fillets. The 600 MPa treatment reduced bacteria count by 6–8 log (CFU/g) for 7–14 days, and the 450 MPa treatment reduced bacteria count by 4–8 log (CFU/g) for 3–14 days, depending on the microorganism. The increased pressure had an impact on flavour, aroma strength and juiciness. The 300 MPa pressure significantly reduced flavour, aroma strength and juiciness, and 450 MPa produced breast fillets with the weakest aroma. Increasing pressure increased cooking loss and colour by increasing L*, a* and b* values. Moreover, elevated pressure increased hardness, cohesiveness, gumminess and chewiness, as well as improved freshness of meat by reducing VBN. Pressure of 450 MPa and higher induced lipid oxidation. The results demonstrate that high pressure treatment is an effective technology in reducing bacterial spoilage and extending shelf-life of chicken breast fillet, however it may have a negative impact on some quality and sensory characteristics.     

Effect of isothiocyanates from horseradish (Armoracia rusticana) on the quality and shelf life of tofu

The effects of isothiocyanates (ITCs) on microbiological, physicochemical, and sensory properties were investigated in tofu on days 0, 2, 4, 6, 8, and 10 of storage at 10 °C. When compared to the control (8.14 log CFU/g), the 200 ppm of ITCs (4.40 log CFU/g) effectively retarded the growth of microflora in tofu after 10 days of storage. The initial pH slightly declined after 10 days of storage, ranging between 5.81 and 6.14. The control showed significantly higher acid values over storage. Compared to the control, the preference to sensory attributes (color, taste, odor, chewiness, and over acceptance) of ITC-treated samples was highly rated after 10 days of storage. The ITCs can be used as an alternative for extending the shelf life and improving the safety of tofu.     

Microbial profile of buffalo sausage during processing and storage

A study was made on the microbial levels of buffalo sausage during preparation and storage at 4 ± 1 °C. Microbial counts in raw minced meat were, total plate count (TPC) (log cfu/g) 5.41 ± 0.25; coliforms (MPN/g) 23.2; Staphylococcus aureus (log cfu/g) 1.57 ± 0.11; yeasts and molds (log cfu/g) 2.29 ± 0.07 and lactic acid bacteria (LAB) (log cfu/g) 0.60 ± 0.20. Sausage emulsion showed similar trend in microbial counts with minimal microbial contamination during the preparation of emulsion. Cooked buffalo sausage gave the following microbial counts: TPC (log cfu/g) 3.75 ± 0.31; coliforms (MPN/g) 0.2; LAB (log cfu/g) 0.07 ± 0.01; yeast and molds (log cfu/g) 0.72 ± 0.07. S. aureus, Clostridium perfringens and Bacillus cereus were not detected in cooked sausages. These results indicate that steam cooking for 45 min followed in the study was effective in reducing the microbial counts substantially. The investigation revealed that shelf life of cooked buffalo sausage was 31 days in either vacuum or CO₂ at 4 ± 1 °C. The results indicated that spoilage of vacuum packed cooked buffalo sausage was likely due to LAB while microflora other than LAB may be responsible for spoilage of CO₂ packed cooked buffalo sausage. The study suggests that measures such as low initial microbial counts, hygienic precautions during preparation of sausage, steam cooking for 45 min, vacuum or CO₂ packing and storage at 4 ± 1 °C would control the microbial growth and provide wholesomeness and safety to the buffalo sausage.     

Study of physical–chemical and sensorial properties of irradiated Tommy Atkins mangoes (Mangifera indica L.) in an international consignment

Tommy Atkins mangoes from Brazil were sent to Canada after being submitted to a thermal treatment (46.1 °C, 110 min – control) and to a gamma irradiation treatment (doses 0.4 and 1.0 kGy). The fruits were stored at 11 °C during 10 days until the international transportation and kept at an environmental condition (22 °C) during 12 days, where their physical–chemical and sensorial properties were evaluated. Analysis of visual parameters showed that irradiation treatment influenced the maturity index. Mass loss was around 5% for all fruits, from the three treatments, and incidence of end rot was lower for irradiated fruits. Physico-chemical analysis presented some significant differences and irradiated mangoes at 1.0 kGy had lower values than control ones (p ? .05) for texture for each day of analysis. Sensory evaluation demonstrated that panelists perceived few differences among treatments.     

Safe and shelf-stable natural casing using hurdle technology

Safe and shelf-stable natural casing were prepared using a combination of hurdles viz. reduced water activity, packaging and gamma irradiation. Washed lamb intestines were treated with common salt to reduce water activity to 0.80 ± 0.02, packed in polyethylene bags and subjected to gamma-irradiation (5 and 10 kGy). Control non-irradiated samples had high total viable counts (10⁶ CFU/g), aerobic spores (10³ CFU/g), spores of sulphite reducing clostridia (10³ CFU/g), potentially pathogenic bacteria such as staphylococci (10⁴ CFU/g) and coliforms (10² CFU/g). Treatment with gamma radiation resulted in a dose dependent reduction in counts of these microbes. A dose of 5 kGy was sufficient to reduce total viable counts by three log cycles; spore counts by two log cycles and completely eliminate staphylococci and coliforms. Samples subjected to a 10 kGy dose were devoid of any viable microbes. The reduced water activity of the product prevented growth of the microbes in natural casings during storage at room temperature. Sausages prepared using hurdle processed natural casing were examined for sensory and textural properties. It was observed that product acceptability and mechanical strength was not affected by radiation processing. Our studies indicated that shelf-stable and safe natural casing could be prepared using a combination of hurdles.     

Effect of gamma irradiation on Listeria ivanovii inoculated to iceberg lettuce stored at cold temperature

A low-dose gamma irradiation considerably reduced the total plate counts, psychrotrophic bacteria, lactic acid bacteria, and inoculated Listeria ivanovii on shredded iceberg lettuce. The total plate count of the lettuce irradiated at 1.0 kGy was reduced by 3.38 log₁₀ cfu/g on 0 storage day and to below the limit of detection (<2 log₁₀ cfu/g) as the cold storage was extended. Irradiation at 0.5 kGy effectively reduced the psychrotrophic bacterial counts and lactic acid bacterial counts in the lettuce to below the limit of detection (2 log₁₀ cfu/g). Irradiation at 1.0 kGy reduced L. ivanovii inoculated onto the shredded iceberg lettuce to below the limit of detection. The results showed that an irradiation at 1 kGy eliminates the bacterial contamination from the lettuce sample without any sensorial quality defect.     

Effect of γ irradiation on quality-maintaining of fresh-cut lettuce

The effects of irradiation on microorganisms and physiological quality of fresh-cut lettuce were evaluated during storage at 4 °C. The total bacterial counts on fresh-cut lettuce irradiated with 1.0 kGy were reduced by the order of 2.35 Log CFU/g, and the total coliform group were lowered to less than 30 MPN (most probably number)/100 g. The polyphenoloxidase activity of fresh-cut lettuce was significantly inhibited by irradiation. In addition, the loss of vitamin C of fresh-cut lettuce irradiated with 1.0 kGy was significantly (α = 0.05) lower than that of non-irradiated. The best treatment of maintaining quality of fresh-cut lettuce appeared to be 1.0 kGy irradiation.     

Effect of orange dietary fibre,oregano essential oil and packaging conditions on shelf-life of bologna sausages

The objective of this work was to study the effect of orange dietary fibre (1%) (ODF), oregano essential oil (0.02%) (OEO) and the storage conditions (vacuum, air and modified atmosphere) on the shelf-life of bologna sausage. Samples with ODF + OEO stored in vacuum packaging showed the lowest TBA values. ODF + OEO samples stored in vacuum packaging showed the lowest aerobic and lactic acid bacteria counts. The sensory evaluation scores were similar for samples with ODF + OEO and stored either in air or vacuum packaging. Orange dietary fibre and oregano essential oil could find a use in the food industry to improve the shelf-life of meat products.     

Sensory quality and food safety of boneless chicken breast portions thawed rapidly by submersion in hot water

Boneless chicken breast portions were thawed by submersion in hot water (60 °C) and compared to refrigerator thawing. Thawing in hot water was significantly quicker (2–8.5 min) than refrigerator thawing (10–15.5 h). Thawing time in hot water increased with an increase in meat thickness. Sensory panelists could not distinguish a difference between hot water versus refrigerator thawed and subsequently grilled chicken breast portions. A model for Salmonella growth predicts that thawing chicken breast at the slowest rate in this study (0.5 °C/min) would result in a lower increase in the Salmonella concentration than that expected for room temperature storage for 4 h.     

Inactivation of 3-strain cocktail pathogens inoculated into Bajirak jeotkal,salted, seasoned,and fermented short-necked clam (Tapes pilippinarum), by gamma and electron beam irradiation

The objective of this study was to determine the efficacy of gamma and electron beam irradiation of the food-borne pathogens including 3-strain cocktail of Listeria monocytogenes (ATCC 19114, 19115, and 19111), Staphylococcus aureus (ATCC 6538, 25923, and 29213), and Vibrio parahaemolyticus (ATCC 17802, 33844, and 27969) in Bajirak jeotkal (8% salt), salted, seasoned and fermented short-necked clam, commercially available in the market. Irradiation (0.5, 1, 2, and 5 kGy) significantly reduced the initial microbial level not only immediately after irradiation but also during storage at 10 °C for 4 weeks (P < 0.05). No viable cells were detected at 5 kGy of irradiation at a detection limit of 10¹ CFU/g. Gamma irradiation was more effective than electron beam irradiation, and yielded D₁₀ values of 0.64, 0.63, and 0.29 kGy for L. monocytogenes, S. aureus, and V. parahaemolyticus, and those of electron beam irradiation were 0.79, 0.81, and 0.36 kGy, respectively. Results suggest that a low dose irradiation can improve the microbial quality and reduce the risk by the food-borne pathogens of Bajirak jeotkal, which has limited alternative sterilization methods due to the temperature characteristics of the products. Furthermore, in practical application, the irradiation source should be considered to obtain an effective dose for decontamination.     

Quality assessment of Mediterranean horse mackerel (Trachurus mediterraneus) and blue jack mackerel (Trachurus picturatus) during storage in ice

Sensory, physicochemical and microbiological analyses were carried out on Mediterranean horse mackerel and blue jack mackerel in order to determine quality changes during storage in ice. Sensory results indicated that whole Mediterranean horse mackerel and blue jack mackerel used in this trial had a shelf-life of 10 and 7 days, respectively. Fishtester and Fishchecker measurements showed that the quality of blue jack mackerel had deteriorated more rapidly. Fishtester values of the blue jack mackerel and the Mediterranean horse mackerel were reduced from 59 ± 10.1 to 14.8 ± 2.8 and from 85.3 ± 13.2 to 25.6 ± 7.8, respectively during the storage time. Fishchecker gave red sign (unfit for consumption) for first time on day 7 and day 6 in Mediterranean horse mackerel and blue jack mackerel, respectively. The pH of Mediterranean horse mackerel muscle was consistently lower than the pH of blue jack mackerel muscle during the storage period. The pH values of both species muscle increased gradually with time and pH value equal to 7 had almost coincided with the end of shelf-life. Bacterial loads in both fish species muscle remained rather low prior to day 10 (<6 log₁₀ cfu/g). The longer shelf-life of Mediterranean horse mackerel as determined by sensory evaluation was not reflected in microbiological results suggesting that the difference was due to lower rate of autolysis rather than to reduced microbial activity.     

Consumer awareness and perception to food safety hazards in Trinidad,West Indies

Little is known on consumer perception and awareness to food safety in Trinidad, West Indies. A survey was conducted on 121 consumers who handled meat on food safety knowledge and handling practices at homes. Most (P < 0.01; 83.2%) categorised food safety as ‘very’ important. Consumers differed (P < 0.05) in their perception as to the most feared food hazard. Escherichia coli (89.7%) and Salmonella (85.7%) were most known (P < 0.01) of microbial types. Restaurant (55.0%) was regarded to be the most likely place where food poisoning could occur. There was no distinct (P > 0.05) trust in food safety authorities. Gender had (P > 0.05) no influence on responses. The study highlighted gaps in food safety knowledge and critical violations in food handling.     

Meat species identification based on the loop mediated isothermal amplification and electrochemical DNA sensor

An easy, rapid and sensitive method of detection of the presence of meat species in raw or processed foods is important from cultural, religious, health and commercial perspectives. In this study we have tried to distinguish species-specificity in control and processed pork, chicken and bovine meats using loop mediated isothermal amplicons (LAMP) and disposable electrochemical printed (DEP) chips. LAMP is a nucleic acid amplification method that amplifies target DNA with high specificity, efficiency and rapidity under isothermal condition (63 °C). Electrochemical genosensor with the DEP chips detects the amplicons by Linear Sweep Voltammetry (LSV) observation of DNA–Hoechst33258 interaction on the chip surface. Hoechst33258 interacts with DNA in solution without immobilization of DNA onto the electrode surface eliminating the time consuming probe immobilization step. Our method is more specific and free of unwanted amplifications compared to Multiplexed PCR (M-PCR) method and gave limits of detection of ∼20.33 ng/μl (3 × 10⁴ copies/reaction), ∼78.68 pg/μL (3 × 10² copies/reaction) and ∼23.63 pg/μL (30 copies/reaction) for pork, chicken and bovine species, respectively. Our method of detection is quick, taking only an hour, and it may be useful for food administration laboratories to carry out meat species identification in raw and processed foods.     

Use of gamma irradiation for inactivation of pathogens inoculated into Kimbab,steamed rice rolled by dried laver

The effect of gamma irradiation for inactivating the pathogens inoculated into the ready-to-eat Kimbab, steamed rice rolled by dried laver, was investigated. The pathogens used were Salmonella Typhimurium, Escherichia coli, Staphylococcus aureus and Listeria ivanovii which are important for public health. The growth of four test organisms inoculated (about 10⁶–10⁷ CFU/g) into the Kimbab were sustained by an irradiation treatment during 24 h of storage regardless of the temperature at 10, 20 and 30 °C. Four pathogen inoculated into Kimbab decreased 2–3 log CFU/g by 1 kGy treatment and was not detected after 3 kGy. The D₁₀ value of pathogens inoculated into the Kimbab were 0.31–0.44 kGy among the four organisms. This study indicated that a low dose irradiation can maintain microbial safety for ready-to-eat Kimbab, steamed rice rolled by dried laver.     

Relation between microbial levels of ready-to-eat foods and the monitoring of compliance with HACCP-based own control programs in small Danish food outlets

This study concerns the correlation between monitoring of hygienic levels by public food inspectors and observed microbial levels in two types of food, cream cakes and pasta salads sold by small enterprises. The microbial contents of pasta salads exceeded frequently 7 log CFU g⁻¹ in outlets with highly satisfactory rankings by food inspectors. Contrarily, microbial contents of cream cakes were mostly below 5 log CFU g⁻¹, in relatively high agreement with food inspectors’ ranking. The implications for monitoring compliance with HACCP-based own control programs in small food outlets are discussed.