Changes in the content of biologically active polyamines during storage and cooking of pig liver

Dietary polyamines putrescine (PUT), spermidine (SPD) and spermine (SPM) participate in numerous human physiological processes, including tumour growth. Eight experiments with pig liver were carried out. In two, livers were stored at -18°C for 168 days, in four, livers were stored aerobically (AE), vacuum-packaged (VP) and packaged in a modified atmosphere (MO; 70% N(2) and 30% CO(2), v/v) at +2°C for 9, 21 and 21 days, respectively, and in two, the effects of four cooking treatments were tested. Polyamines were determined as dansyl derivatives using an HPLC method. Distribution of both SPD and SPM in the four main liver lobes was homogenous. The initial SPD and SPM contents in 14 livers 24h after slaughter were 23.3±6.7 and 94.5±19.6mgkg(-1), respectively. The putrescine content was below the limit of detection. The content of SPD and SPM decreased during frozen-storage to about 70% of the initial values. On day-9 of storage, mean SPD and SPM contents decreased to about 85% of the initial values in livers stored in MO and to about 75-80% in AE and VP at 2°C. The decrease continued more extensively in VP than in MO. PUT was detected from day-15 of VP and MO storage. There was a significant decrease in SPD and SPM, to about 70-60% of the initial content during cooking.     

Concentration of biologically active polyamines in meat and liver of sheep and lambs after slaughter and their changes in mutton during storage and cooking

Putrescine (PUT), spermidine (SPD) and spermine (SPM) concentrations using a UPLC method, in chilled mutton, lamb and livers 24 h after slaughter were determined. PUT concentrations were quantifiable only in some samples. Mean SPD concentrations were 4–6, 13.5 and 16.8 mg kg⁻¹ in the meats, sheep and lamb livers, respectively. The respective SPM concentrations were 17–25, 128 and 79 mg kg⁻¹. SPD and SPM losses of about one fifth and half of the initial level, respectively, were apparent in mutton loins stored at −18 °C for 6 months. Significant losses of SPD and SPM were found in mutton loins stored aerobically, vacuum-packaged or in a modified atmosphere at + 2 °C. Boiling and stewing of mutton legs caused SPD and SPM losses of about 40% and roasting of about 60% of the initial content.     

Concentration of biologically active polyamines in rabbit meat, liver and kidney after slaughter and their changes during meat storage and cooking

The concentration of putrescine (PUT), spermidine (SPD) and spermine (SPM) was determined in chilled meat and kidneys of 18 rabbits and in liver of 12 animals 24 h after slaughter. Very low PUT concentrations were detected only in kidneys. Mean SPD levels were 2.2, 2.2, 61.7 and 32.7 mg kg^− 1 in saddle, leg, liver and kidneys, respectively. The respective SPM concentrations were 14.7, 8.0, 115 and 88.4 mg kg^− 1. SPD and SPM losses of about one third of the initial levels were apparent in saddles stored at − 18 °C for 8 months. Losses of both polyamines of about 15-20% of the initial concentrations were found in saddles stored aerobically at + 2 °C for up to 9 days. Stewing of saddles caused significant SPD and SPM losses of about 20-25%, while upon roasting and pan-roasting without oil a decrease of about 50% of the initial concentration was observed.     

Changes in the content of biologically active polyamines during pork loin storage and culinary treatments

Dietary polyamines putrescine (PUT), spermidine (SPD) and spermine (SPM) participate in numerous human physiological processes, including tumour growth. Physicians and dieticians thus need reliable information on their contents in foods. However, data for processed meat are rather limited. Eight experiments with pork loin were therefore carried out. Loins were stored at −18 °C for 168 days in three experiments, in next three ones pork was stored aerobically, vacuum-packaged and packaged in a modified atmosphere (70% N₂ and 30% CO₂, v/v) at +2 °C for 9, 21 and 21 days, respectively. The effects of five usual culinary treatments were tested in two experiments. The polyamines were determined as dansyl derivatives using a HPLC method. Only SPM was determined at levels 20.3–25.2 mg kg⁻¹ in fresh loins; PUT and SPD contents were below the detection limits. SPM content slightly, but significantly (P < 0.05) increased during frozen storage, while it mildly and insignificantly (P > 0.05) decreased during all three variants of cold storage. SPM losses of about 40% of the initial content were observed during boiling, stewing, pan-roasting without oil and breaded pork frying, while roasting caused the loss of about 55%. Similar losses were found for loins processed 24 h and 7 days after slaughter. No SPM content was detectable in broth and grease produced during the processing.     

Content of polyamines in beef and pork after animal slaughtering

Dietary polyamines putrescine (PUT), spermidine (SPD) and spermine (SPM) participate in an array of important human physiological roles, including tumour growth. Physicians and dieticians thus need reliable information on polyamine contents in foods. However, data for both fresh and processed beef and pork are limited. We therefore, determined the initial content of the polyamines, 24 h after slaughtering, in sirloin and rump of 63 young bulls and in loin and leg of 27 pigs of both genders. Polyamines were determined as N-benzamides by micellar electrokinetic capillary chromatography (MECC). PUT and SPD contents in most of the meat samples were negligible. Mean SPM contents were about 22±6 mg kg⁻¹ in sirloin and rump. No significant correlations at P<0.05 were found between the SPM contents in sirloin and rump, likewise between SPM contents and the age and between live weight and type of the efficiency of the bulls. Mean SPM contents in loin and legs of barrows were 26.1±7.0 and 28.4±8.5 mg kg⁻¹, respectively, while the corresponding values in gilts were 22.3±10.6 and 18.3±9.3 mg kg⁻¹.Between the genders the difference in SPM contents in the legs was significant. SPM contents relatively vary widely within the individual kinds of meat, which complicates application of the results for the controlled human nutrition.     

Biologically active polyamines in beef, pork and meat products: A review

Dietary polyamines (PAs) putrescine (PUT), spermidine (SPD) and spermine (SPM) participate in an array of roles in human metabolism. Nevertheless, under some physiological conditions they can be undesirable. Meat and meat products are among important sources of PAs in human nutrition, mainly of SPM. The usual contents of PUT, SPD and SPM in fresh beef and pork are <2, <5 and 20-40mgkg(-1), respectively. Current information on changes of PAs during meat storage corresponds with PUT formation by bacterial activity mainly of pseudomonads and Enterobacteriaceae. However, data on SPD and SPM changes during meat chill-storage have been inconsistent. Culinary processing of meat probably does not change SPD and SPM levels. PUT can be formed in different meat products in relation to the microbial population of the raw materials used and the hygienic level of manufacturing process. SPD and SPM contents seem to remain stable during processing of non-fermented meat products or decrease during dry-cured ham ripening. PUT contents increase commonly to 60-140mgkg(-1) in dry spontaneously fermented sausages, however, contents up to several hundreds mgkg(-1) are not extraordinary. Starter cultures are usually able to decrease PUT formation considerably. SPD and SPM contents in dry fermented sausages are comparable with levels typical for fresh meat. Data on SPD and SPM changes during ripening and storage are inconsistent. A decrease of the both polyamines during a storage period has been usually reported.     

Contents of biologically active polyamines in chicken meat,liver, heart and skin after slaughter and their changes during meat storage and cooking

Dietary polyamines, putrescine, spermidine (SPD) and spermine (SPM), participate in an array of important physiological roles, including tumour growth. Thus, reliable information on polyamine content in foods has been needed. We therefore determined polyamine contents in chilled chicken meat and giblets (n = 20) and skin (n = 10) 24 h after slaughter. The polyamines were determined, after extraction with perchloric acid, as dansyl derivatives, using an HPLC method. Mean SPD values were 4.8, 10.2, 11.4, 48.7 and 12.1 mg kg⁻¹ and SPM values were 36.8, 38.0, 24.3, 133 and 82.7 mg kg⁻¹ in breast, thigh, skin, liver and heart, respectively. Significant statistical correlations between SPD and SPM contents were observed in breast, thigh, skin and liver, whereas correlations were insignificant in heart. An increase of SPD and SPM was apparent in breasts and thighs stored at −18 °C for 6 months; however, it was significant only for SPM in thighs. The losses of both SPD and SPM were statistically insignificant during storage of aerobically packaged breasts up to 9 days at +2 °C. A significant decrease of SPM to about 60% of the initial contents was observed in both vacuum-packaged and in modified atmosphere (20% CO₂ and 80% O₂)-stored breasts on day 21 at +2 °C. For both SPD and SPM, roasting, grilling and frying of fresh breasts caused losses of about 40–60% of the initial contents (higher than boiling and stewing). Similarly, losses of SPM, due to roasting of breasts frozen for 3 or 6 months, were higher than those caused by stewing. Putrescine was detected only sporadically and at levels close to the detection limit of 1.0 mg kg⁻¹ (fresh matter).     

Effect of lactate-enhancement, modified atmosphere packaging, and muscle source on the internal cooked colour of beef steaks

Earlier studies on lactate-mediated colour stability in beef did not address the possible influence on cooked colour. Our objective was to examine the effect of lactate-enhancement, muscle source, and modified atmosphere packaging (MAP) on the internal cooked colour of beef steaks. Longissimus lumborum (LL) and Psoas major (PM) muscles from 16 (n = 16) beef carcasses (USDA Select) were randomly assigned to 4 enhancement treatments (non-injected control, distilled water-enhanced control, 1.25% and 2.5% lactate), and fabricated into 2.54-cm steaks. Steaks were individually packaged in either vacuum (VP), high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), or carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), and stored for 0, 5, or 9 days at 1 °C. At the end of storage, surface and internal colour (visual and instrumental) was measured on raw steaks. Steaks were cooked to an internal temperature of 71 °C, and internal cooked colour (visual and instrumental) was evaluated. Lactate-enhancement at 2.5% level resulted in darker (P < 0.05) cooked interiors than other treatments. Interior cooked redness decreased (P < 0.05) during storage for steaks in VP and HIOX, whereas it was stable for steaks in CO. Our findings indicated that the beef industry could utilise a combination of lactate-enhancement and CO MAP to minimise premature browning in whole-muscle beef steaks.     

Destruction of acid- and non-adapted Listeria monocytogenes during drying and storage of beef jerky

Presence of Listeria monocytogenes in ready-to-eat meat products is not desired and strictly regulated in the US. Inactivation of acid- and non-adapted L. monocytogenes inoculated on beef slices was studied during drying and storage of jerky formulated with modified marinades. The inoculated (five-strain composite, c. 6·2 log cfu cm⁻²) slices were subjected to marinades (4°C, 24 h) prior to drying (60°C for 10 h) and aerobic storage (25°C for 60 days). The predrying marinade treatments tested were, first, no treatment, control (C); second, traditional marinade (TM); third, double amount of TM modified with 1·2% sodium lactate, 9% acetic acid, and 68% soy sauce containing 5% ethanol (MM); fourth, dipping into 5% acetic acid for 10 min and then applying the TM (AATM); and fifth dipping into 1% Tween 20 for 15 min and then into 5% acetic acid for 10 min followed by the TM (TWTM). Bacterial survivors on beef slices were determined during drying and storage using tryptic soy agar with 0·1% pyruvate (TSAP), and PALCAM agar. Results indicated that drying reduced bacterial populations in the order of pre-drying treatments TWTM (5·9–6·3 log cfucm⁻² in 10 h)≥AATM≥MM>TM≥C (3·8−4·6 log cfucm⁻² in 10 h). No significant (P≥0·05) difference was found in inactivation of acid-adapted and non-adapted inocula within individual treatments. Bacterial populations dropped below the detection limit (−0·4 log cfucm⁻²) as early as 4 h during drying or remained detectable even after 60 days of storage depending on acid-adaptation, predrying treatment, and agar media. These results indicated that acid-adaptation may not increase resistance to microbial hurdles involved in jerky processing and that use of modified marinades may improve the effectiveness of drying in inactivating L. monocytogenes.     

Modelling the effect of gas composition on the gas exchange rate in Perforation-Mediated Modified Atmosphere Packaging

Modified Atmosphere Packaging (MAP) relies on modification of the atmosphere inside a package, achieved by the natural interplay between the respiration of the product and the transfer of gases through the package. Polymeric films are the most usual packaging material but because of the increase in the consumption of fresh-cut products with a higher respiration rate and higher tolerance to CO₂, alternative materials are being investigated. The perforation-mediated package is one of those alternatives, where the regulation of the gas exchange is achieved by single or multiple tubes that perforate an otherwise impermeable packaging material. From an engineering point of view, the transport of gases through perforations is a complex phenomenon that involves diffusion gradients together with co-current transport of multiple species, with oxygen entering the package and carbon dioxide leaving it. The influence of one species transport in the other has not been studied so far. The objective of this work was to analyse the effect of initial concentration of CO₂ on the effective mass transfer coefficients of O₂ (K_O2) and CO₂ (K_CO2) in perforation-mediated MAP. K_O2 ranged from (6.99 ± 0.05) × 10⁻⁸ (m³ s⁻¹) to (28.50 ± 0.01) × 10⁻⁸ (m³ s⁻¹) and for K_CO2 from (6.45 ± 0.04) × 10⁻⁸ (m³ s⁻¹) to (28.32 ± 0.01) × 10⁻⁸ (m³ s⁻¹). On average K_O2 decreased by approximately 15% with an increase of CO₂ initial concentration from 25% to 100%. K_CO2 was insensitive to the composition of the gas mix. The permeability ratio (β) varied from 0.73 ± 0.01 to 1.34 ± 0.01. A mathematical model considering the co-current effect of CO₂ flux on the gas exchange rate for O₂ was developed. These results suggest that there is a significant drag effect in the gas exchange process that should be taken into consideration when designing perforation-mediated MAP.     

The triacylglycerol preparation of conjugated linoleic acid reduces lipid oxidation in irradiated, cooked ground beef patties

It is proposed that conjugated linoleic acid (CLA) would depress the lipid oxidation caused by irradiation of cooked, aerobically stored ground beef patties. The free fatty acid (FFA–CLA) and triacylglycerol (TAG–CLA) preparations of CLA were added at 0%, 1%, 2%, or 4% during the grinding process. Patties were irradiated at 1.5–2.0 kGy and frozen at −20 °C. Subsequently, the patties were tempered to 4 °C, cooked to 70 °C and held at 4 °C for 7 d. Enrichment of ground beef with CLA increased the cis-9,trans-11 and CLA trans-10,cis-12 CLA isomers in ground beef patties, even after cooking. Weight loss (P = 0.03) and percentage fat (P = 0.05) were higher in irradiated beef patties than in control patties. Irradiation decreased the concentration of α-linolenic acid (18:3n − 3) in the ground beef by over 60% (P = 0.07), whereas thiobarbituric acid reactive substances (TBARS) values were higher (P = 0.004) in irradiated beef patties than in control patties. The 1% concentration of added TAG–CLA reduced TBARS in irradiated ground beef patties, whereas 2% and 4% FFA–CLA depressed TBARS (CLA type × percentage interaction P = 0.04). Irradiation increased the cardboard and painty aromatic attributes (P  0.05), and FFA–CLA preparation increased the painty aromatic attribute and afterburn aftertaste, but these effects were not observed with the TAG–CLA preparation (CLA type × treatment interaction P < 0.04). Adding 1% TAG–CLA to ground beef during grinding can reduce lipid oxidation in irradiated, cooked ground beef patties without the negative aftertastes associated with the FFA–CLA preparation.     

Behaviour of Listeria monocytogenes in the presence of Listeria innocua during storage of minced beef under vacuum or in air at 0°C and 10°C

Minced beef was inoculated with low levels (1·2–1·7 log₁₀cfu g⁻¹) of Listeria monocytogenes or Listeria innocua, or a combination of the two strains. Inoculated samples were stored at 0 or 10°C under two packaging atmospheres (aerobic and vacuum) for up to 28 days and surviving organisms recovered on Palcam Agar. The only significant increases in numbers of Listeria spp. occurred in samples held at 10°C under aerobic conditions. In vacuum packs, growth of both strains was inhibited. Under aerobic conditions meat pH increased from an initial value of pH 5·85 to c. 8·85 within 28 days. The pH of vacuum packaged meat declined to c. 4·95 during the same period. These differences in pH may be related to differences in the nature and effects of different background microflora that were observed to develop under each of these packaging conditions.Pseudomonas spp. predominated in aerobically stored beef, whereas in vacuum packed beef lactic acid bacteria predominated. No significant differences were observed between the growth rates of Listeria spp. inoculated into beef mince in pure and mixed culture. This suggests that the more frequent prevalence of Listeria innocua than Listeria monocytogenes in meat and meat products is not due to overgrowth or inhibition of the pathogen (Listeria monocytogenes) by the non-pathogen(Listeria innocua) during low-temperature storage.     

Biochemical and thermal characterization of crude exo-polygalacturonase produced by Aspergillus sojae

Crude exo-polygalacturonase enzyme (produced by Aspergillus sojae), significant for industrial processes, was characterized with respect to its biochemical and thermal properties. The optimum pH and temperature for maximum crude exo-polygalacturonase activity were pH 5 and 55 °C, respectively. It retained 60–70% of its activity over a broad pH range and 80% of its initial activity at 65 °C for 1 h. The thermal stability study indicated an inactivation energy of E_d = 152 kJ mol⁻¹. The half lives at 75 and 85 °C were estimated as 3.6 and 1.02 h, respectively. Thermodynamic parameters, ΔH^*, ΔS^* and ΔG^*, were determined as a function of temperature. The kinetic constants K_m and V_max, using polygalacturonic acid as substrate, were determined as 0.424 g l⁻¹ and 80 μmol min⁻¹, respectively. SDS-PAGE profiling revealed three major bands with molecular weights of 36, 53 and 68 kDa. This enzyme can be considered as a potential candidate in various applications of waste treatment, in food, paper and textile industries.     

Environmental factors affect efficacy of some essential oils and resveratrol to control growth and ochratoxin A production by Penicillium verrucosum and Aspergillus westerdijkiae on wheat grain

This study determined the efficacy of three essential oils (bay, clove and cinnamon oil) and the antioxidant resveratrol (0–500 μg g⁻¹) on the control of growth and ochratoxin A (OTA) production by Penicillium verrucosum and Aspergillus westerdijkiae (=A. ochraceus) under different water activity (a_w, 0.90, 0.95, 0.995), and temperature (15, 25 °C) conditions on irradiated wheat grain. The most effective treatment (resveratrol) was then tested on natural grain. The ED₅₀ values for growth inhibition by the oils were 200–300 μg g⁻¹ at the a_w and the temperatures tested. For resveratrol, this varied from <50 μg g⁻¹ at 0.90–0.95 a_w to >350 at 0.995a_w at both temperatures. The ED₅₀ values for the control of OTA were slightly lower than for control of growth, with approx. 200 μg g⁻¹ required for the oils and 50–100 μg g⁻¹ of the antioxidant, at 0.90/0.95a_w and both temperatures. In wet grain (0.995a_w), higher concentrations were required. For growth there were statistically significant effects of single-, two- and three-way interactions between treatments except for concentration×temperature and concentration×temperature×essential oil/antioxidant treatment. For OTA control, statistically significant treatments were a_w, temperature×a_w, concentration×temperature, treatment×concentration, and three-way interaction of concentration×a_w×treatment for P. verrucosum and A. westerdijkiae. Subsequent studies were done with the best treatment (resveratrol, 200 μg g⁻¹) on natural wheat grain with either P. verrucosum or A. westerdijkiae at 0.85–0.995a_w and 15/25 °C over 28 days storage. This showed that the populations of the mycotoxigenic species and OTA contamination could be reduced by >60% by this treatment at the end of the storage period.     

Effect of heat and thermosonication treatments on watercress (Nasturtium officinale) vitamin C degradation kinetics

The use of ultrasound in food processing creates novel and interesting methodologies, which are often complementary to classical techniques. In this work, the effect of heat and the combined treatment heat/ultrasound (thermosonication) on the thermal degradation kinetics of vitamin C in watercress (Nasturtium officinale) was studied in the temperature range of 82.5 to 92.5 °C. First order reaction kinetics adequately described the vitamin C losses during both blanching processes.The activation energies and the reaction rates at 87.5 °C for heat (H) and thermosonication (Ts) treatments were, respectively, E_avitCH = 150.47 ± 42.81 kJ mol^− 1 and E_avitCTs = 136.20 ± 60.97 kJ mol^− 1, and k_{87.5 °CvitCH} = 0.75 ± 0.10 min^− 1 and k_{87.5 °CvitCTs} = 0.58 ± 0.11 min^− 1. No significant differences (P > 0.05) were detected between both treatments. The thermosonication treatment was found to be a better blanching process, since it inactivates watercress peroxidase at less severe blanching conditions and consequently retains vitamin C content at higher levels. The present findings will help to optimise the blanching conditions for the production of a new and healthy frozen product, watercress, with heat and a new blanching process methodology.

Industrial relevance

Thermosonication blanching can be useful since it reduces processing times, and consequently minimizes the adverse effects of heating on watercress quality. This new application will provide good material, in terms of vitamin C, for further processes, and can be an excellent alternative to the traditional heat treatment.     

Migration of α-tocopherol from an active multilayer film into whole milk powder

Antioxidant active packaging is a promising technology for whole milk powder (WMP) protection. In this study, the migration of α-tocopherol from a multilayer active packaging (made of high density polyethylene, ethylene vinyl alcohol and a layer of low density polyethylene containing the antioxidant) to WMP was studied. A model based on the Fick’s diffusion equation was used to calculate the diffusion coefficients (D) of α-tocopherol as 2.34 × 10⁻¹¹, 3.06 × 10⁻¹¹, and 3.14 × 10⁻¹¹ cm² s⁻¹ at 20, 30 and 40 °C, respectively. The D at 20 °C was different from those at 30 and 40 °C (P < 0.05); but it was similar at 30 and 40 °C. This low influence of temperature on the migration of α-tocopherol from 20 to 40 °C assures the release at real storage and commercialization conditions in regions with warm/hot climate. The antioxidant delivering system delayed the lipid oxidation of WMP and it was more effective at 30 and 40 °C since the rate of oxidative reactions was higher at these temperatures than at 20 °C.     

The survival of Campylobacter jejuni in red meats stored at different temperatures

The survival of 4 strains of Campylobacter jejuni was studied in raw minced beef and raw pork sausage mixture stored in plastic stomacher bags at freezer temperatures (−19°C) for up to 10 weeks, refrigirator temperatures (< 10°C) for 6 days and 22°C for 24 h. At each of the 3 storage temperatures survival was better in minced beef. Similarly, there was less variation in percentage survival between the 4 strains in minced beef than in sausage mixture after storage at each temperature. Detailed studies were carried out with one strain of C. jejuni. Viable counts were relatively unchanged in minced beef at refrigerator temperatures and 22°C, but showed a decrease in corresponding samples of sausage mixture. At freezer temperatures decreases in count of approximately 1 log unit were observed during the first week for both meats followed by a more gradual decrease. The effect of desiccation by exposure was studied in minced beef and lamb outer carcass meat (breast) at refrigerator temperatures (≤ 10°C). Decreases in viable count were observed in lamb carcass meat after 32 h although large variations were sometimes observed between duplicate samples for the same strain of C. jejuni. Counts were unchanged in exposed minced beef after storage for 48 h.     

Survival kinetics of Ephestia kuehniella eggs during 46–75 °C heat treatment

The effect of heat treatment on the survival of Ephestia kuehniella eggs was examined. Samples of 60 eggs were immersed in hot water at constant temperature in the 46–75 °C range for 5–1200 s. Following heat treatment and cooling, the eggs were stored at 24 ± 1 °C in a growth chamber for 7 days before survival evaluation. Statistical analysis of the data demonstrated that the thermal survival kinetics were best represented by a first-order reaction. The rate constant had an Arrhenius-type dependence over the 54–75 °C temperature range. Kinetic parameters were estimated by non-linear regression. The activation energy (E_a) and rate constant (k_ref) at the reference temperature (T_ref = 64.8 °C), were determined as 102.2 ± 6.2 kJ mol⁻¹ and 0.061 ± 0.003 s⁻¹, respectively, over the 54–75 °C temperature range. A 0.01% survival rate was obtained after 50 s at 75 °C. The data at temperatures below 50 °C were not in accordance with those at higher temperatures. Above this temperature, mortality was likely due to physiological disorders, as noted on a DSC thermogram.     

Inhibition of Clostridium sporogenes growth in mascarpone cheese by co-inoculation with Streptococcus thermophilus under conditions of temperature abuse

The ability of a biological control system to inhibit the outgrowth of Clostridium sporogenes spores during storage of mascarpone cheese under temperature-abuse conditions was investigated. Challenge studies were carried out on mascarpone cheese artificially contaminated with spores of C. sporogenes (10 cfu g⁻¹), and with or without the coinoculum of a Streptococcus thermophilus strain (10⁵cfu g⁻¹). During storage at 4, 12, and 25°C, the outgrowth of clostridia spores, the growth of S. thermophilus, and the pH changes were evaluated at 10, 20, 30, and 40 days. In mascarpone cheese stored at 4° and 12°C, S. thermophilus and C. sporogenes did not show any growth. The initial pH (6·14) of the product also remained unchanged. During storage at 25°C S. thermophilus grew up to about 10⁷cfu g⁻¹after 10 days, resulting in a pH decrease of mascarpone cheese to values close to 4·5. The cell number decreased progressively during storage reaching values near to 10¹cfu g⁻¹after 40 days, whereas product acidity remained constant. C. sporogenes, when inoculated alone, also grew at 25°C. The cell number increased to levels of about 10⁷cfu g⁻¹after 20–40 days of storage according to the different mascarpone cheese lots used. No growth was found when C. sporogenes was co-inoculated in mascarpone cheese with S. thermophilus and stored at 25°C. The study on the behaviour of C. sporogenes, known as a non-toxigenic variant of Clostridium botulinum, allowed us to obtain useful information for setting up an effective biological control system to inhibit growth of the toxigenic species as well. The use of an additional barrier, besides refrigerated storage, may help to maintain the safety of mascarpone cheese in the event it was exposed to elevated temperatures.     

Biogenic amines and polyamines in liver,kidney and spleen of roe deer and European brown hare

Cadaverine (CAD), histamine (HIS), tyramine (TYR) and the polyamines putrescine (PUT), spermidine (SPD) and spermine (SPM) were determined in liver, kidney and spleen of hunted roe deer (n = 39) and European brown hare (n = 20) 3 and 6 h post mortem, respectively. Median concentrations (mg/kg fresh weight) of CAD and TYR were <5 mg/kg for organs of both species, whereas median HIS concentrations were higher in spleen (14.6 and 11.6 mg/kg for hare and roe deer, respectively) and lowest in liver. Maximum PUT concentration was 72.9 mg/kg, but median values were ≤7.8 mg/kg. Mean SPD concentrations were 8.5, 10.7 and 42.9 mg/kg for liver, kidney and spleen of roe deer, and 37.2, 24.4 and 52.0 mg/kg for hare. Mean SPM concentrations were higher (94.6, 79.9, 102.2 and 111.2, 82.8, 91.1 mg/kg, respectively). SPM concentrations in the organs of the male roe deer were significantly higher than in those of females. SPM:SPD ratios (weight base) were in the order of 2:1 for spleen, and higher for liver and kidney. SPM and SPD were correlated significantly (r = 0.42–0.47). Although variations of polyamine concentrations are partially associated with species, organ, age and gender, the relative contribution of individual factors deserves further study.