Safety and quality of ready-to-eat dry fermented sausages subjected to E-beam radiation

The inactivation kinetics in the death of Listeria innocua NTC 11288 (more radioresistant than five different strains of Listeria monocytogenes) and Salmonella Enterica serovar Enteritidis and S. enterica serovar Typhimurium by E-beam irradiation has been studied in two types of vacuum-packed RTE dry fermented sausages (“salchichon” and “chorizo”) in order to optimize the sanitation treatment of these products. A treatment of 1.29 kGy was calculated to reach the food safety objective (FSO) according to the “zero tolerance” criterion for the three strains. No irradiation treatment was necessary to meet the 10² c.f.u./g microbiological criterion for L. monocytogenes. Dry fermented sausages treated with 2 kGy had negligible sensory (appearance, odour and taste) modifications. Therefore, this treatment produces safe dry fermented sausages with similar sensory properties to the non-irradiated product.     

Chitosan effects on quality properties of Greek style fresh pork sausages

The effect of chitosan (0.5% and 1%) added individually or in combination with nitrites (150 ppm) on microbiological (Total Viable Counts, Lactic acid bacteria, Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae, yeasts and moulds), physicochemical-chemical (pH, chemical composition, lipid oxidation) and sensory properties of fresh pork sausages stored at 4 °C for 28 days was investigated. Chitosan addition resulted in significant (p < 0.05) inhibition of microbial growth, while nitrites did not seem to protect sausages from microbial spoilage. A gradual reduction of nitrites was observed till the end of storage, when nitrites were almost depleted in all nitrite containing samples. The rate of lipid oxidation in fresh pork sausages was significantly decreased (p < 0.05) by addition of increasing levels of chitosan, while samples containing both chitosan and nitrites showed the lowest malondialdehyde (MDA) values, indicating a synergistic antioxidative effect. Consequently, the samples containing the combination of nitrites and chitosan at any level deteriorated less rapidly and were judged as more acceptable than all the other samples.     

Use of natural antioxidants from lyophilized water extracts of Borago officinalis in dry fermented sausages enriched in ω-3 PUFA

An evaluation of the capacity of a lyophilized water extract of borage leaves to delay the lipid oxidation process in dry fermented sausages enriched with ω-3 PUFAs has been performed. Lyophilized extract (340 ppm) showed an antioxidant capacity equivalent to 200 ppm of a butylhydroxyanisol (BHA) and butylhydroxytoluene (BHT) mixture. Two batches of dry fermented sausages enriched in ω-3 PUFA were developed. One of them was supplemented with a synthetic antioxidants mixture (200 ppm of BHA + BHT) and the other one with natural antioxidants (340 ppm of lyophilized water extract of borage leaves). Furthermore, a traditional formulation of this type of dry fermented sausage (Control), was also manufactured. The natural extract gave rise to lower amount of volatile compounds (including hexanal), than the mixture of synthetic antioxidants (2202 and 2713 ng dodecane/g dry matter, respectively). TBARS and Cholesterol Oxidation Products (COPs) did not show significant differences between products with different antioxidants. The sensorial analysis showed that lyophilized water extracts of borage leaves did not affect the sensorial properties of the products. From the economical and safety standpoints, the use of a by-product (borage leaves) and water as extracting solvent are valuable alternatives for obtaining natural antioxidants to be added to dry fermented sausages enriched in ω-3 PUFA.     

Effectiveness of spinosad combined with diatomaceous earth against different European strains of Tribolium confusum du Val (Coleoptera: Tenebrionidae): Influence of commodity and temperature

Laboratory bioassays were carried out to assess the effects of combining spinosad at 0.01, 0.1 and 0.5 ppm, with the diatomaceous earth (DE) formulation SilicoSec at rates of 150, 300 and 600 ppm, against larvae and adults of three different populations of Tribolium confusum du Val (Coleoptera: Tenebrionidae), originating from different European countries (Greece, Portugal and Denmark). Tests were conducted on wheat and maize at 25 and 30 °C. Survival of T. confusum larvae was assessed after 7 d exposure and survival of adults was assessed after 7 d and 14 d of exposure. At each dose of spinosad, survival of T. confusum individuals decreased as the rate of DE increased. As temperature increased, the efficacy of spinosad and Silicosec applied either alone or in combination also increased. The efficacy of spinosad alone was slightly higher on maize than wheat, while the reverse was noted for all the tested combinations of spinosad with DE as well as in the case of the application of DE alone. The strain from Portugal was always the least susceptible of the three tested. Our study indicates that it is possible to combine low doses of DE (<600 ppm) with spinosad (<1 ppm) to control adults and larvae of T. confusum, especially at temperatures >25 °C.     

Bacteriological quality of “doubles” sold by street vendors in Trinidad and the attitudes, knowledge and perceptions of the public about its consumption and health risk

The bacteriological loads of “bara”, “channa”, condiments/spices and ready-to-consume “doubles” sold by street vendors in St. George and Caroni counties of Trinidad were determined. Questionnaires were administered to 100 vendors from both counties to determine which of their practices had effect on the bacteriological quality of the products. In addition, a total of 300 randomly selected members of the public in both counties were interviewed using questionnaires, to assess their attitudes, knowledge and perceptions concerning “doubles” consumption. Of a total of 196 samples each of “bara”, “channa”, condiments/spices and ready-to-eat “doubles” tested, the log₁₀ mean (±SD) total aerobic plate count (TAPC) per g was 4.87±5.51, 5.79±6.61, 6.26±6.77 and 6.88±7.91, respectively. The difference was statistically significant (P<0.05; χ²). Applying a recommended maximum standard of log₁₀ TAPC per g of 5.00, 10 (5.1%), 19 (9.7%), 57 (29.1%) and 78 (39.8%) of 196 samples of “bara”, “channa”, condiments/spices and ready-to-consume “doubles”, respectively, were deemed unfit for human consumption. Vendor practices, which significantly affected the prevalence of unfit “doubles” were re-use of leftover product (P=0.01), wearing of hand gloves (P=0.02), availability of water at sale outlet (P=0.0008) and source of water (P=0.0008). Consumption of “doubles” was more common amongst East Indians (69.2%) than other races (30.8%) (P<0.001) and amongst individuals who were aware that “doubles” can cause food-poisoning (61.4%) compared with individuals who did not have the awareness (36.0%) (P<0.03). Age, gender and occupational status of individuals did not significantly (P>0.05) affect consumption of “doubles”. The high prevalence of ready-to-consume “doubles” assessed unfit for human consumption coupled with a significantly higher proportion of consumers than non-consumers being aware that the product could cause food-poisoning, definitely poses a health risk to consumers of “doubles” in the population. Enforcement of sanitary practices during the preparation and sale of “doubles” should reduce the health risk.     

Microbial and physicochemical succession in fermented sausages produced with bacteriocinogenic culture of Lactobacillus sakei and semi-purified bacteriocin mesenterocin Y

The influence of the bacteriocinogenic culture Lactobacillus sakei (10⁵/g) and semi-purified bacteriocin mesenterocin Y (2560 AU/kg) on the safety and quality of traditional Croatian fermented sausages was investigated. The addition of Lb. sakei and/or mesenterocin Y reduced microbial counts (P < 0.05) in the final products. After 28 days of ripening, coagulase-negative cocci decreased 1.5–2.0 log, yeasts 1.2–1.4 log and enterococci 1.7–2.7 log. In the case of the addition of Lb. sakei, the lactic acid bacteria count was significantly (P < 0.05) higher at day 7 of ripening, and was accompanied by a lower pH and a higher amount of lactic acid (P < 0.05). In the final product the amount of acetic acid was significantly lower. More intensive proteolysis and an increase in ammonia content were found at the beginning of fermentation, and in the second phase of ripening in the control samples, respectively. The free fatty acid concentration was significantly lower during the entire ripening process compared to the control (P < 0.05). Semi-purified mesenterocin Y did not affect the sensory properties of the sausages, whilst the addition of Lb. sakei enhanced them.     

Enhancement of the nutritional status and quality of fresh pork sausages following the addition of linseed oil, fish oil and natural antioxidants

Fresh pork sausages (pork shoulder, pork back fat, water, rusk and seasoning) were manufactured where 15% of the pork back fat was substituted with linseed oil (LO) or fish oil (FO). Green tea catechins (GTC) and green coffee antioxidant (GCA) were added to both LO (LGTC 200 and LGCA 200) and FO (FGTC 200 and FGCA 200) substituted sausages at a level of 200 mg/kg. Raw and cooked pork sausages were either over-wrapped with oxygen permeable film (aerobic storage) or stored in modified atmosphere packages (MAP) containing 80% O₂:20% CO₂ or 70% N₂:30% CO₂, respectively for 7 days at 4 °C. Effects on fatty acid profiles, lipid oxidation, colour and sensorial properties were investigated. α-Linolenic acid increased from 1.34% (control) to 8.91% (LO) and up to 11.2% (LGTC 200 and LGCA 200). Addition of fish oil increased levels of EPA from 0.05% (control) to 2.83% (FO), 3.02% (FGTC 200) and 2.87% (FGCA 200) and DHA levels increased from 0.04% (control) to a maximum of 1.93% (FGTC 200). Lipid oxidation was low in raw and cooked linseed oil containing sausages. GTC (200 mg/kg) significantly (P < 0.05) reduced lipid oxidation in raw fish oil containing sausages after 7 days of storage. Colour parameters in raw pork sausages were unaffected by the packaging atmosphere. L^* lightness values were lower (P < 0.05) in LGTC 200 and a^* redness values lower (P < 0.05) in LGTC 200 and FGTC 200 after 7 days of storage. Sensory scores of cooked pork sausages were unaffected by linseed oil addition. Flavour and overall acceptability scores in cooked fish oil containing sausages were improved by GTC addition. Results obtained demonstrate potential for the production of nutritionally enhanced fresh pork sausages.     

Effect of a linseed diet on lipid composition, lipid peroxidation and consumer evaluation of French fresh and cooked pork meats

Twenty castrated pigs [(Large-White × Landrace) × (Pietrain)] (52.9 ± 5.1 kg initial body weight) were fed a control or a linseed diet containing 4.2% of extruded linseed. Animals were slaughtered at 106.6 ± 3.7 kg live weight. There was no effect of diet on pig performance. Feeding the linseed diet increased the contents of n−3 polyunsaturated fatty acids (PUFA) in chops (raw and cooked), chitterlings sausages, country style pâté, garlic sausages, liver pâté, and smoked belly. However, docosahexaenoic acid (DHA) level was not affected by the linseed diet. The linseed diet produced a robust decrease in the n−6/n−3 and linoleic acid (LA)/α-linolenic acid (ALA) ratios (<4). Feeding pigs with a high n−3 PUFA diet led to a decrease in the oxidative stability of chops, in contrast to smoked bellies for which thiobarbituric acid-reactive substances (TBARS) values were not affected by the diet. However, there was no deleterious effect on consumer overall appreciation of the meat.     

Usefulness of calcium lactate, citrate and gluconate for calcium enrichment of dry fermented sausages

Food manufacturers are interested in new ways to improve the nutritional value of their meat products. In this study, calcium lactate, gluconate and citrate have been added to dry fermented sausages in an attempt to determine whether they are useful for enriching these meat products with calcium. The sausages were manufactured with different amounts of pork backfat (6, 15, and 30%) and the salts were added in sufficient amounts to 100 g of sausage to give 20% and 30% of the recommended daily allowance (RDA) of calcium established by the Institute of Medicine of the USA (1000 mg/day). The lower concentration of whichever calcium salt (20% of RDA), was the most sensorially adequate. With this amount these sausages can be considered a “source of calcium”. In addition, we found that the lower backfat percentage (6%) compromises the acceptability of the product.     

Microbial quality of “doubles” sold in Trinidad

A cross-sectional study was conducted to determine the prevalence and characteristics of Escherichia coli, Staphylococcus aureus, Bacillus spp. and Salmonella spp. in “bara”, “channa”, condiments/spices and ready-to-eat “doubles” sold by vendors in the St. George and Caroni counties of Trinidad. Of 196 samples of each of “bara”, “channa”, condiments/spices and ready-to-eat “doubles” examined, E. coli was detected in 0 (0.0%), 14 (7.1%), 96 (49.0%) and 67 (34.2%), respectively; Staphylococci were isolated from 104 (53.1%), 71 (36.2%), 129 (65.8%) and 123 (62.8%) samples, respectively; and Bacillus spp. were recovered from 22 (11.2%), 85 (43.4%), 100 (51.0%) and 88 (44.9%) samples, respectively. Salmonella spp. were not isolated from any sample. Of the 177 isolates of E. coli recovered from all sources, 9 (5.1%), 7 (4.0%) and 47 (26.6%) were mucoid, haemolytic and non-sorbitol fermenters (NSF), respectively, but none agglutinated with O157 antiserum. Of 427 staphylococcal isolates, 130 (30.4%) were confirmed as S. aureus of which 20 (15.4%) were haemolytic and 84 (64.6%) pigmented, while 17 (20.7%) of 82 strains of S. aureus tested produced enterotoxins. Ready-to-eat “doubles”, a popular food in Trinidad, therefore pose a potential health risk to consumers due to the high level of contamination with bacteria.     

Effect of reducing nitrate and nitrite added to dry fermented sausages on the survival of Salmonella Typhimurium

Salmonella is one of the pathogens that most frequently contaminate pork processing lines. Several hurdles can control this organism in dry fermented sausages, among them is nitrite. However, the traditional use of nitrate/nitrite in the meat industry is being questioned due to their involvement in nitrosamine formation. In this study, minced pork and sausages inoculated with Salmonella Typhimurium were prepared with 150 ppm NaNO₃ and 150 ppm NaNO₂ (maximum amounts allowed by EU), and with a reduction of 25% and 50%. The absence of nitrate/nitrite favored Salmonella growth, with 2–2.5 log cfu/g higher counts at the end of ripening, compared to nitrate/nitrite added batches. The 50% reduction showed the same inhibitory effect as the maximum amounts. Nitrate/nitrite represented an essential hurdle to control Salmonella even when pH and a_w were below the values considered as minimum for its growth. The effect of this reduction on other pathogens should be considered.     

Microbial formation of nitrite-cured pigment,nitrosylmyoglobin, from metmyoglobin in model systems and smoked fermented sausages by<Emphasis Type="Italic"> Lactobacillus fermentum</Emphasis> strains and a commercial starter culture

Two Lactobacillus fermentum strains (JCM1173 and IFO3956) were evaluated for their ability to generate nitrosylated derivatives of myoglobin either in broth media or fermented sausages. For comparison, a commercial starter culture was also included. All bacteria species investigated converted brown metmyoglobin into red myoglobin derivatives when incubated separately in broth, but only the two lactobacilli showed a signal for nitrosylmyoglobin as measured by electron spin resonance spectroscopy. In smoked sausages with added bacteria culture the highest amount of nitrosylmyoglobin was observed in the centre of sausage with added L. fermentum, but colour formation in sausages with 60 ppm of nitrite added was more pronounced. An outer peripheral zone of all fermented sausages contained levels of nitrosylmyoglobin comparable to nitrite-cured sausages. Nitrogenous gasses from smoke may, however, cause this zone to be formed. Depending on a further optimisation of the processing parameters, the bacteria's ability to generate NO could form the basis for production of cured meat products without the use of nitrite/nitrate.     

Chitosan effects on quality properties of Greek style fresh pork sausages

The effect of chitosan (0.5% and 1%) added individually or in combination with nitrites (150 ppm) on microbiological (Total Viable Counts, Lactic acid bacteria, Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae, yeasts and moulds), physicochemical-chemical (pH, chemical composition, lipid oxidation) and sensory properties of fresh pork sausages stored at 4 °C for 28 days was investigated. Chitosan addition resulted in significant (p < 0.05) inhibition of microbial growth, while nitrites did not seem to protect sausages from microbial spoilage. A gradual reduction of nitrites was observed till the end of storage, when nitrites were almost depleted in all nitrite containing samples. The rate of lipid oxidation in fresh pork sausages was significantly decreased (p < 0.05) by addition of increasing levels of chitosan, while samples containing both chitosan and nitrites showed the lowest malondialdehyde (MDA) values, indicating a synergistic antioxidative effect. Consequently, the samples containing the combination of nitrites and chitosan at any level deteriorated less rapidly and were judged as more acceptable than all the other samples.     

Effect of freeze-dried leek powder (FDLP) and nitrite level on processing and quality characteristics of fermented sausages

Fermented sausages were produced with 0.84% and 1.68% freeze-dried leek powder (FDLP), providing 75 and 150 mg/kg NaNO₃, respectively, and three levels of added nitrite (0, 75, and 150 mg/kg NaNO₂). A control treatment was also produced with 150 mg/kg NaNO₂. Sausages with FDLP were darker and yellower (p < 0.05) than the control. Higher FDLP levels produced less red, yellower and darker sausages (p < 0.05). Lower FDLP levels resulted in higher (p < 0.05) sensory scores for external appearance, flavour and overall acceptability. No differences were found among the treatments with FDLP plus 75 or 150 ppm NaNO₂ in TBA value, lightness, redness (cross section), redness stability, yellowness, texture parameters and sensory firmness, flavour and overall acceptability. The use of 0.84% FDLP and 75 ppm NaNO₂ is considered more appropriate for the production of fermented sausages, as it results in a 50% reduction in added nitrite.     

Effect of curing and cooking on flavonols and anthocyanins in traditional varieties of onion bulbs

The stability of the major flavonol glucosides and anthocyanins was studied in two regional varieties of Portuguese onion (a white variety “branca da Póvoa” and a red variety “vermelha da Póvoa”). White and red onions from 2007 and 2008 harvests were subjected to field curing with and without light, but the red cultivar from 2008 was also subjected to typical domestic processing, including chopping and different cooking treatments. Field curing resulted in increases in quercetin content compared to levels at lifting, especially important for all white bulbs (33–40% increase). Flavonol and anthocyanin levels in onions cured in the dark were similar to those obtained in bulbs cured in the light. The treatments chopping followed by refrigerated storage, oven roasting and frying, did practically not contribute to modify the total levels of flavonols. Moderate microwave cooking did not affect to the flavonol content, but intense microwave treatment cause flavonol losses of 16% and 18% for quercetin 3,4′-diglucoside (QdG) and quercetin 4′-glucoside (QmG), respectively. Boiling onions for 30 min leaded losses of quercetin glycosides, which leached to the boiling water without being degraded at 37% and 29% for QdG and QmG, respectively. Boiling for 60 min had more severe effects, since it caused the degradation of quercetin derivatives at 53% and 44% for QdG and QmG, respectively. For anthocyanins, the severity of the cooking treatments was in the following order: frying > boiling > roasting (microwave roasting > oven roasting).     

Effects of curing sodium nitrite additive and natural meat fat on growth control of Listeria monocytogenes by the bacteriocin-producing Lactobacillus curvatus strain CWBI-B28

In realistic model meat systems, the separate and combined effects of fat content and sodium nitrite on the antilisterial activity of the bacteriocin of Lactobacillus curvatus CWBI-B28 were studied. In laboratory fermentations where Listeria monocytogenes was co-cultured at 4 °C with bacteriocin-producing CWBI-B28 in lean pork meat (fat content: 13%) without added nitrite, a strong antilisterial effect was observed after one week. The effect was maintained for an additional week, after which a slight and very gradual rebound was observed. Both added nitrite (20 ppm) and a high-fat content (43%) were found to antagonise this antilisterial effect, the Listeria cfu count reached after six weeks being 200 times as high in high-fat meat with added nitrite than in lean meat without nitrite. This antagonism could not be attributed to slower growth of the bacteriocin-producing strain, since CWBI-B28 grew optimally in fat-rich meat with 20 ppm sodium nitrite. Bacteriocin activity was also measured in the samples. The observed activity levels are discussed in relation to the degree of antilisterial protection conferred.     

Persistence of pasture feeding volatile biomarkers in lamb fats

Recent studies have evidenced volatile biomarkers in ruminant tissues that distinguish between exclusive pasture and exclusive concentrate diets. As ruminants usually alternate these diets, we set out to monitor the persistence of volatile tracers of pasture diet in perirenal fat and caudal subcutaneous fat in lambs (n = 28) fed on pasture and then fattened at increasing levels with concentrate: Four groups of lambs (n = 7) were stall-finished to achieve a final weight gain of 0, 4, 8, and 12 kg, respectively. Thirty nine pasture diet tracers including terpenes, 2,3-octanedione and toluene were found that distinguish between the four different diets in both tissues. According to their clearance rates monitored in the adipose tissues of lambs fattened with different amounts of concentrate, different types of persistence were evidenced. Most of the compounds exhibited a “short” persistence, e.g. 2,3-octanedione and terpenes, while some displayed a “medium” or “long” persistence. Finally, performing discriminant analysis on ratios of tracers from the two adipose tissues enabled the correct differentiation of the four different diets.     

A comparison of three amperometric phenoloxidase–Sonogel–Carbon based biosensors for determination of polyphenols in beers

Three phenoloxidases based biosensors were successfully developed using as electrochemical transducer a new type of electrode recently developed by our group: the “Sonogel–Carbon electrode”. The employed enzymes were Trametes versicolor laccase (Lac), Mushroom tyrosinase (Tyr), and Horseradish peroxidase (HRP). Immobilization step was accomplished by doping the electrode surface with a mixture of the individual enzyme and Nafion ion exchanger as additive-protective. The biosensor responses, optimized in beer real samples, were evaluated for five individual polyphenols. It was found that the developed biosensors were sensitive to nanomolar concentrations of the tested polyphenols. As example, the limit of detection, sensitivity, and response linear range for caffeic acid for Nafion-Lac/Sonogel–Carbon biosensor were 0.06 μmol L⁻¹, 99.6 nA μmol⁻¹ L, and 0.04–2 μmol L⁻¹, respectively. The stability and reproducibility of the biosensors were evaluated by applying them directly to beer real samples. It has been demonstrated that the Nafion-Lac/Sonogel–Carbon system is the more stable with a relative standard deviation of 3.3% (n = 10), maintaining 84% of its stable response for at least three weeks. Estimation of polyphenol index in eight lager beers and a comparison of the results with those obtained by a classical method was carried out.     

Rapid determination of collagen in meat-based foods by microwave hydrolysis of proteins and HPAEC-PAD analysis of 4-hydroxyproline

A rapid microwave procedure for protein hydrolysis coupled with High Performance Anion Exchange Chromatography and Pulsed Amperometric Detection (HPAEC–PAD) was developed to quantify the amino acid 4-hydroxyproline in meat and meat-based products. This innovative approach was successfully applied to determine collagen content (4-hydroxyproline × 8) as the index quality of meat material employed in the preparation of typical meat sausages (“Mortadella di Bologna PGI” and “Salamini italiani alla cacciatora PDO”) and fresh filled pastas. Microwave hydrolysis showed a precision and accuracy similar to traditional hydrolysis (RSD% from 0.0 to 6.4; relative error 1.4–10.0%) with a reduction in the hydrolysis time from 24 h to 20 min. HPAEC–PAD allowed detection of 4-hydroxyproline without pre or post-column derivatization and the use of non-toxic eluents.