Influence of processing on the extension of shelf-life of Nagli-fish (Sillago sihama) by gamma radiation

Studies were carried out to evaluate the microbiological profile, shelf-life and quality of Nagli fish (Sillago sihama) subjected to gamma irradiation. Non-irradiated samples were unacceptable organoleptically after 7–8 days of storage at 1–2°C while irradiated samples (2 and 3 kGy) were acceptable up to 19 days. Dressing prior to irradiation had no additional advantage to shelf-life over whole fish. Total bacterial count (TBC), total volatile basic nitrogen (TVBN), trimethylamine (TMA) and sensory evaluation data revealed no significant differences between whole and dressed fish. Salmonella sp. were not detected in 3 kGy-irradiated samples whereas 2 kGy destroyed Vibrio parahaemolyticus and Staphylococcus aureus. Listeria monocytogenes and Yersinia enterocolitica were not detected but non-pathogenic species such as L. grayi, L. murrayi, and Y. tuberculosis were present in the fish prior to irradiation. Irradiation doses of 2 and 3 kGy destroyed Yersinia sp. and Listeria sp., respectively. These organisms were not detected during storage of the treated fish.     

枯草芽孢杆菌素延长香肠货架期的研究

研究了枯草芽孢杆菌B.C119代谢产生的细菌素对香肠中细菌的抑制作用,并与山梨酸钾的抑菌效果进行对照,对香肠进行感官指标、pH、菌落总数的测定.结果表明:枯草芽孢杆菌素能有效的抑制香肠中细菌的繁殖,从而延长香肠的货架期,并且效果要优于山梨酸钾.     

用复合防腐剂延长汀州烧大块货架期的研究

用Nisin、乳酸钠、山梨酸钾、茶多酚构成的复合防腐剂,对汀州烧大块进行处理,真空包装后贮藏于25℃环境中,每隔10d检测菌落总数、pH值和进行感官评定.结果表明:复合防腐剂可有效地延长烧大块的货架期;保鲜效果最佳的配比为 Nisin0.4g/kg、乳酸钠4.5g/kg、山梨酸钾1.0g/kg、茶多酚0.3g/kg.     

Use of neutral electrolysed water (EW) for quality maintenance and shelf-life extension of minimally processed lettuce

Experiments were conducted to determine the effectiveness of different treatments based on the use of neutral electrolysed water (EW) on fresh-cut lettuce. EW was diluted to obtain different free chlorine concentrations (120, 60 and 12 ppm) and to compare with standard washing treatment of 120 ppm chlorine solution. Shelf-life quality and safety markers were studied at the beginning and at the end of the 7-day-storage at 4 °C. The use of EW decreased the respiration rate of the samples which might be related with the observed reduction in microbial spoilage. The use of EW also increased the activity of a browning-related enzyme (polyphenoloxydase) although sensory results showed all samples as acceptable at the end of the 7 day-storage. Perhaps longer storage time might increase the risk to browning development in the samples treated with EW. The highest EW concentration (120 ppm free chlorine) was the most effective treatment in reducing sample microbial load; however this treatment also affected the final produce with effects such as loss of turgor, plasmolysis and a reduction in mineral content.Results suggest an intermediate EW concentration with 60 ppm free chlorine could be an alternative to 120 ppm chlorine (from sodium hypochlorite) for sanitizing fresh-cut vegetables, reducing to half the amount of chlorine used and maintaining the antimicrobial effectiveness and without differences affecting the quality. However further studies will be necessary in order to observe the effect of the oxidising capacity of EW on other quality and safety markers as pathogens and nutritional content.Industrial relevanceChlorine solutions have been widely used to sanitise fruit and vegetables in the fresh-cut industry. However, the association of chlorine with the possible formation of carcinogenic chlorinated compounds in water has called into question the use of chlorine in food processing. The efficacy in controlling the microbial load and browning of samples treated with electrolysed water shows it as a promising decontaminant agent for fresh-cut lettuce. Due to the high oxidising potential of the EW quality requirements must be balanced to obtain the optimal treatment conditions keeping satisfying safety levels. The use of EW-60 showed similar safety and quality (browning) results as the use of chlorine or double EW concentration (EW-120). However the treatment EW-120 affected negatively the textural properties. The study suggests the use of EW-60 as an alternative to sodium hypochlorite solution with 120 ppm available chlorine, obtaining similar safety and quality results and reducing the amount of chlorine needed. Further investigations in the effect of EW on lettuce, such as those on pathogens or nutritional markers (e.g. carotenoids and vitamin C) are recommended in order to explore this alternative that might reduce the increasingly concerning use of chlorine to decontaminate this type of product.     

Bacterial microflora of carp (Cyprinus carpio) and its shelf-life extension by essential oil compounds

The microflora of common carp (Cyprinus carpio) skin, gill and intestine were analysed and the antimicrobial activities of garlic oil and nine constituents of essential oils (allyl isothiocyanate, carvacrol, cinnamaldehyde, citral, cuminnaldehyde, eugenol, isoeugenol, linalool and thymol) against the carp isolates were studied to identify compounds that might extend the shelf-life of carp fillet. A total of 90 isolated strains were identified to belong to seven genera: Acinetobacter (6), Alcaligenes (2), Bacillus (2), Flavobacterium (20), Micrococcus (2), Moraxella (6) and Pseudomonas (4), and two families Enterobacteriaceae (14) and Vibrionaceae (34). The dominant micro-organisms of carp were found to be Flavobacterium (37%) and Vibrionaceae (33%) in skin, Flavobacterium (33%) in gill and Vibrionaceae (63%) and Flavobacterium (37%) in intestine. Against these isolates, thymol, carvcarol and cinnamaldehyde had the strongest antimicrobial activities, followed by isoeugenol, eugenol, garlic oil, and then citral. The antimicrobial properties of the other constituents tested (cuminnaldehyde, linalool and allyl isothiocyanate) were low. In tests of mixed compounds, a combination of carvacrol and thymol had the highest antimicrobial activity. Moraxella, Flavobacterium and Vibrionaceae were more sensitive to the compounds, whereas Alcaligenes strains were resistant. Dipping carp fillets in a solution of 0.5% carvacrol and 0.5% thymol before storage at 5°C and 10°C reduced both the total microbial load by about 100-fold and the Volatile Bases Nitrogen (VB-N), as compared with controls. In addition, dipping treatment delayed bacterial growth and extended the shelf-life of the fillets from 4 to 12 days at low temperature (5°C). However, the treated and control fillets showed little difference during storage at 10°C. Data from sensory evaluation showed that dipped fillets in 1% (carvacrol+thymol) extended the shelf-life of carp fillets by 8 and 4 days at 5° and 10°C, respectively. Thus, carvacrol and thymol dipping can improve the microbial stability of fish fillets by removing bacteria and by inhibiting bacterial growth.     

Effect of oxygen- and carbon dioxide-enriched atmospheres on shelf-life extension of refrigerated ground pork

The oxidation of the lipids and myoglobin of ground pork meat stored in oxygen- and carbon dioxide-enriched atmospheres at 1 °C has been studied. Elevated oxygen levels (80-100%) depressed myoglobin oxidation, increasing the time to 50% metmyoglobin formation from four to about thirteen days. Twenty per cent carbon dioxide greatly reduced the rate of lipid oxidation, extending the time to reach a TBA number of 5 from five to about twelve days. Tocopherol and ascorbic acids were efficient inhibitors of lipid oxidation but citric acid was not.     

Effects of bactericides and modified atmosphere packaging on shelf-life of Chinese shrimp (Fenneropenaeus chinensis)

Effects of different bactericides and modified atmosphere packaging (MAP) on aerobic plate counts (APCs), total volatile base-nitrogen (TVB-N) and organoleptic evaluation of overall acceptable score (OA score) of Chinese shrimp (Fenneropenaeus chinensis) during cold storage were investigated. Results indicated that APC in MAP(40%CO₂/30%O₂/30%N₂) shrimp treated with compound bactericide reached 10⁷ cfu/g on the 13th day of storage, while that of ozonated water or water control treatments exceed 10⁷ cfu/g on the 9th day. APC in shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide reached close to 10⁷ cfu/g at day 13, while that of air treatment exceed 10⁷ cfu/g. TVB-N value in MAP(40%CO₂/30%O₂/30%N₂) shrimp treated with compound bactericide was slightly higher than the upper threshold of 30 mg/100 g on the 17th day, while that of ozonated water treatment or water control increased to or over the threshold value on the 9th day. TVB-N value in shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide were significantly lower than that of air control on the 17th day (P ≤ 0.01), with a value of 33.6 mg/100 g and 42-47.6 mg/100 g respectively, compared to 78.4-86.8 mg/100 g in air control. The lowest OA score of MAP(40%CO₂/30%O₂/30%N₂) whole and decapitated shrimps treated with compound bactericide appeared on the 17th and 21th day, respectively, compared with the 9th day in whole shrimp and the 13th day in decapitated shrimps treated with ozonated water and water control. The lowest OA score of whole and decapitated shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide appeared on the 17th and 21th day, respectively, compared with the 13th and 17th day in air control. In conclusion, when combined the parameters determined together, the shelf-life of Chinese shrimp at 2 ± 1 °C, either whole or decapitated, treated with MAP (40%CO₂/30%O₂/30%N₂) and 100%CO₂ after soaking with compound bactericide were 13 and 17 days, respectively.     

Preservation and shelf-life extension of shrimps and clams by high hydrostatic pressure

Clam ( Venus gallina ) and shrimp ( Parapenaeus longirostris ) samples were high hydrostatic pressure (HHP) treated at 200, 220 and 250 MPa at 25, 30, 40 and 50 °C for 10 and 20 min. Based on the results of microbial reduction, the best combinations of HHP treatments were determined as 250 MPa, 50 °C, 10 min for shrimps and 220 MPa, 50 °C, 10 min for clams. HHP-treated samples stored at 25 °C (room tempertur) and 4 °C (refrigeration temperature) were analysed. According to the results evaluated, shelf-life of shrimps was found to be 12 and 16 days for storage at room and refrigeration temperatures, respectively, as compared with 4 days for non-HHP-treated samples at 4 °C. Similarly shelf-life for the clam samples was found to be 12 days for storage at room temperature and 18 days for storage at refrigeration temperature as compared with 4 days for non-HHP-treated samples at 4 °C.     

草莓气调、涂膜、臭氧等的保鲜研究

利用高二氧化碳和低氧的条件,结合臭氧处理和可食性涂膜,对草莓进行了贮藏保鲜的研究。2.5%O2 16%CO2结合4.3mg/m3浓度臭氧预处理,并采用可食性膜涂膜,结果货架寿命延长到了8～10d。1#和2#涂膜处理在草莓的贮藏保鲜上优于3#、4#和CK涂膜对照组。结果表明,通过涂膜的草莓在糖分含量、酸度含量、花色苷含量的变化图中,1#、2#和对照组比较这些成分变化明显偏缓,而且细胞膜透性和褐变指标、商品率都表现出经过涂膜的草莓效果明显优于其它组。     

Inhibitory effects of microencapsulated allyl isothiocyanate (AIT) against Escherichia coli O157:H7 in refrigerated, nitrogen packed, finely chopped beef

Allyl isothiocyanate (AIT) is an effective inhibitor of various pathogens, but its use in the food industry is limited by its volatility and pungency. The objective of this study was to overcome the volatility of AIT by microencapsulation and evaluate its antimicrobial effectiveness against Escherichia coli O157:H7 in chopped beef. Chopped beef was aseptically prepared and inoculated with a five-strain cocktail of E. coli O157:H7 to yield 4 or 8 log10 cfu/g. AIT was microencapsulated in gum acacia to yield 3.7-54.8 mg AIT/g at a ratio of 1:4 and freeze dried. Microcapsules at 5% or 10% (w/w) were then added to experimental samples that were packed under nitrogen, and stored at 4 degrees C for 18 days. Samples were analyzed for numbers of E. coli O157:H7 and the aerobic mesophilic bacteria (TAC) at 3-day intervals. AIT at 4980 ppm eliminated both low and high levels of inoculated E. coli O157:H7 after 15 and 18 days of storage, respectively. AIT at 2828 ppm reduced E. coli by 2.7 log10 cfu/g by 18 days of storage. AIT levels <1000 ppm were not more effective in reducing E. coli survival than the control treatment without AIT addition. AIT at 170-1480 ppm had negligible effects on the TAC, and while 4980 ppm kept TAC levels 相似文献   

Effects of packaging atmospheres on shelf-life quality of ground ostrich meat

Fresh ground ostrich meat was packaged under high oxygen (O2), high nitrogen (N2), vacuum (VAC) and ambient air (AIR) atmospheres, stored at 4 ± 1 °C and displayed under 1700 ± 100 lux of fluorescent lighting for 9 days. The meat was evaluated for changes in typical shelf-life characteristics consisting of pH, color properties (CIE L^∗, a^∗, b^∗, and total color difference, ΔE), oxidative changes (thiobarbituric acid value and hexanal content) and bacterial counts (total viable cell, coliform, lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp.) Initial meat pH was 6.16 and declined slightly during storage. TBA values and hexanal content were highest in O2 and lowest (P ? 0.05) in VAC and N2 atmospheres. Surface lightness (L^∗) and redness (a^∗) were highest in O2 packaging initially, decreasing (P ? 0.05) by day 9. ΔE of the ground ostrich increased during storage in only O₂ and AIR packaging. All packaging methods had generally similar effects on microbial outgrowth. Total aerobic bacteria attained >10⁶ CFU/g meat between day 3 and day 6. Ground ostrich meat was below saleable quality in less than 6 days based on all of the meat attributes. For O2 packaging however, quality based on lipid oxidation and color properties indicated a shelf-life of less than 3 days. Oxidation is likely the limiting factor for shelf-life of ground ostrich meat.     

Effects of ascorbic acid and pre-packaging on shelf-life and quality of raw and cooked okra (Hibiscus esculentus)

Fresh okra fruits were dipped in aqueous solutions containing 250 and 500 ppm ascorbic acid (AA) or 1000 ppm Tween-20 for 5 min, air-dried, packaged and stored at 2°C. Blackening of the fruits dipped in the Tween-20 solution occurred within 2–4 days of storage while the AA-treated samples showed signs of deterioration after 20 days. Weight loss was greatly reduced in the AA-treated okra samples.The total chlorophyll, oxalate, fibre (hot-water-insoluble materials), ash and moisture contents of all the treated samples remained fairly constant. The maintenance of good quality by AA-treated samples packed in ‘cellophane’ bags was reflected in all aspects of sensory evaluation for cooked okra, even after 29 days of storage. It is concluded that a postharvest dip in 500 ppm ascorbic acid can be beneficial in maintaining texture and greenness of okra.     

The extension of the shelf-life of 'pesto' sauce by a combination of modified atmosphere packaging and refrigeration

Summary This study was intended to extend, by optimizing modified atmosphere packaging (MAP), the shelf-life of the Italian vegetable sauce used for spaghetti and known as 'pesto'. A mathematical model was developed in order to predict gas composition inside the polymeric package (CO₂ concentration). Predictions of equilibration time and equilibrium gas composition showed moderately good agreement with experimental data. A useful extension of pesto shelf-life, up to 120 days, was achieved by adopting a target atmosphere containing, at steady-state, 10% CO₂ and 90% N₂ at 5 °C. Microbial growth was inhibited by the CO₂ levels, but was not accompanied by significant changes in odour and colour.     

Effect of water activity (aw) and irradiation on the shelf-life of fresh noodles

In this work, the effect of water activity (a_w), irradiation and their combination on the preservation of fresh noodles was studied. Microbial growth, pH and sensory characteristics were investigated during 16 days' storage time under 37 °C. The combination of glycerol (3%), propylene glycol (2%), compound phosphate (0.4%) and salt (3%) was proved to be the most effective group which could reduce a_w from 0.979 (control) to 0.900. Under this condition, the shelf-life of fresh noodles could be extended for more than 7 times. Moreover, a synergism between humectants and irradiation treatment was observed in relation to microorganism inhibition and shelf-life extension. For all the irradiated noodles, TPC (total plate count) did never exceed the selected deterioration threshold limit (10⁶ CFU/g) during the entire observation period. When the irradiation dose was 4 kGy or higher, scarcely any bacteria proliferation was observed. Noodle samples irradiated at 4 kGy showed the best pH and sensory stability as the storage time increased.

Industrial relevance

This paper presents an effective and low-cost method to prolong the shelf-life of fresh noodles, which can largely extend the store time of fresh noodles at room temperature, and does not produce any negative changes in sensory attributes. This method will be a new system for food preservation with lots of possible industrial applications. The results of this research also have implications for dumpling skins and other noodle types.     

Pulsed light treatment for the inactivation of selected pathogens and the shelf-life extension of beef and tuna carpaccio

The efficacy of pulsed light to improve the safety of carpaccio has been investigated. Beef and tuna slices were superficially inoculated with approximately 3logcfu/cm(2) of Listeria monocytogenes, Escherichia coli, Salmonella Typhimurium and Vibrio parahaemolyticus. Fluences of 0.7, 2.1, 4.2, 8.4 and 11.9J/cm(2) were assayed. Colour, sensory and shelf-life studies were carried out. Treatments at 8.4 and 11.9J/cm(2) inactivated the selected pathogens approximately by 1logcfu/cm(2), although they modified the colour parameters and had a negative effect on the sensory quality of the product. The raw attributes were not affected by fluences of 2.1 and 4.2J/cm(2) immediately after the treatment, although changes were observed during storage. The inactivation obtained with these fluences was lower than 1logcfu/cm(2), which may not be negligible in case of cross-contamination at a food plant or at a food service facility. Pulsed light showed a greater impact on the sensory quality of tuna carpaccio compared to beef. None of the fluences assayed extended the shelf-life of either product.     

Effects of gelatine type and concentration on the shelf-life stability and quality of marshmallows

The effects of gelatine concentration, bloom strength, and origin on the quality and shelf-life stability of marshmallows were studied. All six sample treatments were carried out under accelerated storage conditions of 25 °C and 75% relative humidity (RH) for 25 weeks. Gelatine A 150 bloom had the highest viscosity because of its highest concentration (2.54%), lowest density and greatest amount of moisture loss producing the hardest marshmallows. Hardness and water activity measurements correlate for all sample treatments indicating that moisture loss is the main mechanism for hardening. With the exception of Gelatine B 2.2%, sugar crystallisation may have occurred in all sample treatments at week 20 which would have an impact on hardness as well. Gel network formation may be contributing towards hardness in Gelatine B 2.2% as there was an increase in hardness but no changes were perceived in water activity.     

Combined effect of ozonated water and chitosan on the shelf-life of Pacific oyster (Crassostrea gigas)

Effects of ozonated water and chitosan treatment on the shelf-life extension of Pacific oysters (Crassostrea gigas) stored at 5 ± 1 °C were studied. Results indicated that ozonated water treatment reduced the total microbial load of fresh oysters by about 10-fold (from 3.2 × 10³ CFU/g to 1.8 × 10² CFU/g) before storage and the microbial flora was different with that of raw samples. The wide-spectrum antibacterial property of chitosan against bacteria isolated from oysters was confirmed, and chitosan concentration of 5.0 g/l was eventually determined for application in oyster preservation. Based on microbiological analysis, biochemical indices determination and sensory evaluation, shelf-lives of 8–9 days for control, 10–12 days for ozonated water treated samples, 14–15 days for chitosan treated samples and 20–21 days for samples with combined treatment were observed, indicating that ozonated water and chitosan have a great potential for oyster preservation.Industrial relevanceAs seafood, Pacific oysters have a short shelf-life. Improvements in the shelf-life of oysters can have an important economic impact by reducing losses and by allowing the products to reach distant and new markets.In this work, Shelf-life of oysters with combined treatment of ozonated water and chitosan doubled, which has great practical meaning, and the process could be fully adopted by the food industry.We also did some research about the changes in microbial flora after ozonated water treatment. This work could help in preservation of oysters when ozone or ozonated water concerned.We discovered Wide-spectrum antibacterial property of chitosan against the strains isolated from raw oysters. The potential for using chitosan as a natural preservative in oysters was approved.