Heat resistance of Byssochlamys nivea, Byssochlamys fulva and Neosartorya fischeri isolated from canned tomato paste

Cultures of heat resistant molds (20) were isolated from spoiled canned tomato paste in order to estimate the pasteurization efficiency applied to commercially canned products. Ascospores of nine strains grown on malt extract agar for 30 days at 30°C, survived heating at 85°C for 20 min when initial numbers were near 10⁵/mL. Of these heat resistant strains were identified: two Byssochlamys nivea, three Byssochlamys fulva and four Neosartorya fischeri strains. Ascospores of all cultures were more heat resistant in tomato juice than in phosphate buffer. Thermal death rate curves were nonlogarithmic but approached logarithmic death rates at higher temperatures. The thermal destruction time for 1 log₁₀ at 90°C was 1.5 min for a Byssochlamys nivea strain, 8.1 min for a Byssochlamys fulva strain and 4.4 to 6.6 min for Neosartorya fischeri strains.     

Bacteria Associated with Spoilage of Braunschweiger

Refrigerated braunschweiger was spoiled mainly by Gram positive, catalase negative coçci identified as Streptococcus faecalis and Pediococcus pentosaceus. P. pentosaceus was isolated from sausage without nitrite held at refrigeration for 12 wk and from sausages made with 156 ppm nitrite stored at 22°C for 21 days. It produced souring and a low pH in the sausage. S. faecalis was isolated from refrigerated sausages and produced a perfumy or scented odor under anaerobic conditions. S. faecalis survived 65°C for 5 min and 60°C for 60 min. P. pentosaceus at levels of 10⁸ cells/ml of broth survived 65°C for 5 min but did not survive when the number of cells was 10³/ml.     

Effects of Frozen Storage on Survival of Staphylococcus aureus and Enterotoxin Production in Precooked Tuna Meat

This study investigated the survival of Staphylococcus aureus in precooked tuna meat for producing canned products during frozen storage (?20 ± 2 °C) as well as its growth and enterotoxin production at 35 to 37 °C after the storage. Samples (50 ± 5 g) of precooked albacore (loin, chunk, and flake) and skipjack (chunk and flake) tuna were inoculated with 5 enterotoxin‐producing strains of S. aureus at a level of approximately 3.5 log CFU/g and individually packed in a vacuum bag after 3 h incubation at 35 to 37 °C. Vacuum‐packed samples were stored in a freezer (?20 ± 2 °C) for 4 wk. The frozen samples were then thawed in 37 °C circulating water for 2 h and incubated at 35 to 37 °C for 22 h. Populations of S. aureus in all precooked tuna samples decreased slightly (<0.7 log CFU/g) after 4 wk of storage at ?20 ± 2 °C, but increased rapidly once the samples were thawed and held at 35 to 37 °C. Total S. aureus counts in albacore and skipjack samples increased by greater than 3 log CFU/g after 6 and 8 h of exposure to 35 to 37 °C, respectively. All samples became spoiled after 10 h of exposure to 35 to 37 °C, while no enterotoxin was detected in any samples. However, enterotoxins were detected in albacore loin and other samples after 12 and 24 h of incubation at 35 to 37 °C, respectively. Frozen precooked tuna meat should be used for producing canned tuna within 6 to 8 h of thawing to avoid product spoilage and potential enterotoxin production by S. aureus in contaminated precooked tuna meat.     

Gas‐producing and spoilage potential of Enterobacteriaceae and lactic acid bacteria isolated from chilled vacuum‐packaged beef

This study aimed to enumerate and identify lactic acid bacteria and Enterobacteriaceae from spoiled and nonspoiled chilled vacuum‐packaged beef and determine their potential to cause blown pack spoilage. These microbial groups were also enumerated in nonspoiled samples and detected in abattoir samples. The potential of isolates to cause ‘blown pack’ spoilage of vacuum‐packaged beef stored at chilled temperature (4 °C) and abuse temperature (15 °C) was investigated. Populations of lactic acid bacteria in exudate of spoiled and nonspoiled samples were not significantly different (P > 0.05), whereas the number of lactic acid bacteria on the surface was significantly higher (P < 0.05) in spoiled samples as compared to nonspoiled samples. The population of Enterobacteriaceae species in exudate and on the surface of samples were significantly higher (P < 0.05) in spoiled packs in comparison with nonspoiled packs. Results of the deterioration potential showed that ‘blown pack’ spoilage was noticeable after 7 days at 15 °C and after 6 weeks at 4 °C for samples inoculated with Hafnia alvei.     

Characterization by Volatile Compounds of Microbial Deep Spoilage in Iberian Dry-Cured Ham

Abstract: In the present study, volatile compounds of spoiled dry-cured Iberian ham with deep spoilage or “bone taint” were analyzed and correlated with level of spoilage and the microorganisms detected. Volatile compounds extracted by a solid phase micro-extraction technique were assayed by gas chromatography/mass spectrometry. The spoiled hams were evaluated sensorially, and the correlations among volatile compounds, spoilage level, and microbial counts were studied. The spoiled hams had higher concentrations of hydrocarbons, alcohols, acids, esters, pyrazines, sulfur compounds, and other minor volatile compounds than unspoiled hams. The sensorial analysis showed that the spoilage level of hams correlated with several volatile compounds, most of them associated with Gram-positive catalase positive cocci and Enterobacteriaceae counts. Cyclic compounds such as cyclohexanone, some ethers, and pyrazines should be considered as indicators to monitor incipient microbial deep spoilage in the elaboration of this meat product.     

Effect of chill storage under different icing conditions on sensory and physical properties of canned farmed salmon (Oncorhynchus kisutch)

This work focuses the sensory and physical properties of canned farmed coho salmon (Oncorhynchus kisutch); the effect of flake ice and slurry ice as previous slaughter and chilling conditions was studied. Hydrolytic chemical changes related to sensory and physical properties were also evaluated in canned salmon. Thermal treatment led to a canned muscle showing higher firmness, lower cohesivity and colour changes (higher L* and b* values; lower a* values); filling oils showed higher turbidity scores and lower L*, a* and b* values than starting oil. Additionally, oxidised and putrid odour development in canned muscle and filling oil was low. However, previous icing condition and time (up to 9 days) provided no changes in canned muscle and filling oil, except for an increasing oxidised odour and turbidity in filling oil with chilling time. Meantime, free fatty acid formation and K value were markedly affected by previous icing system and time.     

Comparison of microbial communities between normal and swollen canned soy sauces using nested PCR‐denaturing gradient gel electrophoresis,HPLC and plate techniques

The microbial community of normal and swollen canned soy sauce was investigated using molecular biological method. The PCR‐denaturing gradient gel electrophoresis (DGGE) profiles showed that four lactic acid bacteria (LAB), including Lactobacillus acidipiscis, L. pobuzihii, L. piscium and another Lactobacillus sp., were involved in the swollen canned samples. Plate technique showed that three diverse species of Bacillus (B. subtilis, B. oleronius and B. flexus) were present in the swollen canned samples. However, much less bacterial contaminants were detected in the normal samples. According to the HPLC analysis, the lactic acid concentrations of the swollen canned samples were significantly higher than those in the normal samples. These results indicated that LAB can play a key role in contributing to the acidisation of the swollen canned soy sauce products. Our results confirmed the existence of Bacillus sp. and LAB in the packaged fermented soy sauce.     

EFFECT OF PROCESSING METHOD ON PRODUCTS MADE FROM SWEET POTATO MASH1

Green and cured (seven days at 29°C and 90% RH) ‘Centennial’ sweet potato roots were used to make and evaluate frozen and canned mashes and canned whole roots. Fried patties and pies were made from each of the processed products. The frozen mash from green roots was higher in pH while the canned mash from green and cured roots was lower in pH and higher in viscosity. The canned mash had the lowest ‘L’ and ‘a’ readings but was rated the highest in color score when made into pies. However, the fried patties were scored higher in color when made from frozen mashes or canned whole roots. Moreover, pies made from low viscous mashes were scored low in texture.     

Measurement of Provitamin A Carotenoids in Fresh and Canned Carrots and Green Peas

The influence of thermal processing (canning) on the carotenoid content of carrots (Daucus carota) and green peas (Pisum sativum) was investigated. Carotenoids extracted from fresh and canned vegetables were separated by column chromatography and quantified using spectrophotometric analysis. Canned canots and green peas had a higher carotenoid content than fresh samples. The apparent increase in canned carrots was mainly due to the loss of soluble solids into the brine during processing. However, the increase of carotenoids in canned green peas was due to the loss of carotenoids by enzymatic activity in fresh green peas during extraction procedures.     

Sensitive determination of bisphenol A and bisphenol F in canned food using a solid-phase microextraction fibre coated with single-walled carbon nanotubes before GC/MS

A reliable and sensitive method for simultaneous determination of bisphenol A (BPA) and bisphenol F (BPF) in canned food by gas chromatography-mass spectrometry (GC/MS) is described after extraction and pre-concentration by a new solid-phase microextraction (SPME) adsorbent. The potential of single-walled carbon nanotubes (SWCNTs) as SPME adsorbent for the pre-concentration of environmental contaminants has been investigated in recent years. This work was carried out to investigate the feasibility of SWCNTs as a headspace SPME adsorbent for the determination of bisphenol derivatives in canned food. Potential factors affecting the extraction efficiency, including extraction time, extraction temperature, desorption time, desorption temperature, and salinity were optimized. Calibration curves were linear (r ²≥ 0.994) over the concentration range from 0.30 to 60 µg kg^?1. For both target analytes, the limit of detection (LOD) at signal-to-noise (S/N) ratio of 3 was 0.10 µg kg^?1. In addition, a comparative study between the SWCNT and a commercial polydimethylsiloxane (PDMS) SPME fibre for the determination of bisphenol derivatives in canned food was conducted. SWCNT fibre showed higher extraction capacity, better thermal stability (over 350°C) and longer life span (over 150 times) than the commercial PDMS fibre. The method was successfully applied to determine BPA in canned food samples which were purchased from local markets. BPA was found in some of the samples within the concentration range from 0.5 to 5.2 µg kg^?1.     

A METHOD FOR MEASURING THE TEXTURE OF MEAT AND THE EFFECT OF NITRITE AND SALT ADDITION ON THE TEXTURE OF CURED MEATS1

An instrumental technique was developed for measuring the texture of canned chopped ham using the 15 cm ² wire extrusion cell of the Ottawa Texture Measuring System. Its measurement efficacy was evaluated by testing enzymatically tenderized ham. This showed that the technique was sensitive to textural changes and that the level of the added enzyme affected the ham's texture exponentially. Nitrite addition to the canned chopped ham product at levels of 0-1000 ppm did not affect its texture. The level of salt used in the curing solution, however, had a marked tenderizing effect. Similarly, compression tests on wieners indicated that nitrite addition did not influence their texture. It was concluded that the characteristic texture of the two products tested cannot be attributed to nitrite addition and that other factors such as the level of salt addition to the canned chopped ham must be responsible.     

An attempt to use a barley fibre preparation containing β-glucan in the production of functional canned meat

Nutritional value and physical and sensory quality characteristics of medium-grounded model canned meat products containing barley fibre preparation Vitacel BG300 (0.0%, 3.0% and 6.0%) were assessed. The results showed that regardless of the type of thermal treatment (pasteurisation and sterilisation), the addition of barley fibre did not significantly (P > 0.05) alter the content of the main nutrients (protein, fat and chlorides) in the block of canned meat product. Increasing the dose of barley fibre from 3.0% to 6.0% significantly increased (P < 0.05) the thermal loss in both pasteurised and sterilised canned meat products. The colour of the blocks of both pasteurised and sterilised canned meat products with barley fibre was significantly (P < 0.05) darker, and the instrumental hardness differed from the corresponding control products. Despite the beneficial nutritional effect of the Vitacel BG300 barley fibre preparation, its use significantly deteriorated the sensory quality of canned meat products.     

Organochlorine pesticides in canned tuna and sardines on the Serbian market

The aim of this study was to determine the level of organochlorine (OC) pesticides in 57 samples of canned tuna and 31 samples of canned sardines in vegetable oil, collected from supermarkets in Serbia. OC pesticides α-HCH, β-HCH, δ-HCH, dichlorodiphenyltrichloroethane (DDT), DDE, DDD, dielderin, endosulfane I, endosulfane II, endosulan sulfate, endrin, endrin ketone, heptachlor, heptachlor epoxide, lindane, aldrin, metoxichlor, cis-chlordane and trans-chlordane were determined using a GS-MS method. The highest concentrations (µg kg^?1, arithmetic means) in canned tuna were for δ-HCH (60.6 ± 97.0) and p, p´-DDT (55.0 ± 25.1), while the corresponding values in canned sardines were for δ-HCH (90.7 ± 102.7) and endosulfane II (78.0 ± 145.9). Mean level for the sum of endosulfans was above the maximum limit in canned sardines (85.0 µg kg^?1). Also, dieldrin (39.7 µg kg^?1) was measured above the ML.     

Microbiological and physico-chemical characterisation of deep spoilage in Spanish dry-cured hams and characterisation of isolated Enterobacteriaceae with regard to salt and temperature tolerance

 The microbiological and physico-chemical characteristics of dry-cured Spanish "serrano" hams with deep spoilage were compared to unspoiled hams, and the evolution of similar characteristics was studied during the early curing stages of previously refrigerated or frozen hams. The results suggest a relationship between deep spoilage and the presence of Enterobacteriaceae, caused by insufficient NaCl concentrations during curing. Strains of Serratia liquefaciens, Enterobacter cloacae and Proteus vulgaris, which comprised the most frequently isolated species of enterobacteria from spoiled hams, were therefore characterised in a model system in order to examine their ability to grow in different NaCl concentrations at different temperatures. Strains isolated from normal hams during early curing stages and from the production environment were included for comparison. The results showed that all strains were able to grow in 7% NaCl at 5  °C, and that strains isolated from spoiled hams did not differ from those isolated from normal hams and from the environment. The NaCl tolerance of strains isolated from spoiled hams was closely linked to incubation temperature, and a reduction in temperature from 5  °C to 2  °C reduced the tolerance significantly. Received: 23 December 1998     

Effect of enterocin EJ97 against Geobacillus stearothermophilus vegetative cells and endospores in canned foods and beverages

Geobacillus stearothermophilus is a thermophilic bacterium typically responsible for the flat-sour spoilage of low-acid canned food with high water activity. Control of vegetative cells and spores of G. stearothermophilus strains CECT 48 and CECT 49 by enterocin EJ97 produced by Enterococcus faecalis EJ97 is described. Both strains were highly sensitive to EJ97 in a culture medium. In samples from canned foods inoculated with a cocktail of vegetative cells or endospores of the two strains and stored at 45 °C for 30 days, viable cell counts were reduced below detection levels. The time course of microbial inactivation depended on the food sample and bacteriocin concentration. Dormant endospores were resistant to EJ97 short-time treatments (5 min), but endospores activated to germinate by heat became bacteriocin sensitive. The simultaneous application of enterocin EJ97 and heat treatments (90 and 95 °C) on dormant endospores had an increased antimicrobial effect that depended both on the bacteriocin concentration and the heat temperature. Results from this study strengthen the potential of enterocin EJ97 for biopreservation against G. stearothermophilus in canned vegetable foods and drinks.     

Multiplex PCR for rapid detection of thermophilic Moorella thermoaceticaand Geobacillus stearothermophilus from canned foods and beverages

A multiplex PCR assay was developed to simultaneously detect the thermophilic spore‐forming bacteria Geobacillus stearothermophilus and Moorella thermoacetica, which are major sources of spoilage in the canned food and beverage industries because of their thermophilic persistence. A total of 294 samples were examined, and none of the samples demonstrated signs of spoilage. Culture‐based assays showed that forty‐five M. thermoacetica isolates were obtained, which was confirmed by multiplex PCR, and G. stearothermophilus was not detected in any of the canned food and beverage, but multiplex PCR analysis identified this species in almost all of the samples. Meanwhile, twelve Bacillus subtilis isolates were found under both aerobic and anaerobic conditions. Multiplex PCR may allow selective detection of species that are present at low levels in complex matrices, or those that cannot be detected by culture‐based methods. Screening for spoilage‐causing micro‐organisms in ingredients and samples from processing lines, together with traditional culture methods, will help risk management and improve hygiene control.     

Tuna Protein Nutritional Quality Changes after Canning

Albacore tuna (Thunnus alalunga) was steamed and canned in soy bean oil and sterilized at 115°C for 55 or 90 min. Proximate composition, total amino acid and available lysine content were determined during different phases of the process. Water and protein were lost in all phases and fat content increased. There was a decrease in available lysine during cooking but no loss in total amino acids. Nutritional evaluation of the protein showed differences in biological value and net protein utilization when the canned tuna was mixed with bread flour.     

Saponin content of food plants and some prepared foods

Quantitative thin layer chromatography was used to estimate the saponin content of 20 common food plants and also of foods prepared from some of them. The food plants found to be richest in saponins were chickpeas (Cicer arietinum), soya beans (Glycine max), lucerne (alfalfa) sprouts (Medicago sativa) and varieties of Phaseolus vulgaris (navy beans, haricot beans, kidney beans). Saponins were not destroyed by processing or cooking. They were present in falafels (prepared from chickpeas), canned baked beans, canned broad beans and protein isolate from faba beans. However, the saponin content of a fermented soya bean product (tempe) was only half that of whole soya beans. Guar meal (Cyamopsis tetragonolobus) contains saponins but only a trace could be detected in samples of guar gum.     

The effect of high pressure treatment on rheological characteristics and colour of mango pulp

The effect of high‐pressure (HP) treatment (100–400 MPa for 15 or 30 min at 20 °C) on the rheological characteristics and colour of fresh and canned mango pulps was evaluated. Differences were observed in the rheological behaviour of fresh and canned mango pulps treated with HP. Shear stress–shear rate data of pulps were well described by the Herschel–Bulkley model. The consistency index (K) of fresh pulp increased with pressure level from 100 to 200 MPa while a steady decrease was noticed for canned pulp. For fresh pulp the flow behaviour index decreased with pressure treatment whereas an increasing trend was observed with canned pulp. Storage and loss moduli of treated fresh pulp with HP increased linearly with angular frequency up to 200 MPa for a treatment time of 30 min while a steady decreasing trend was found for processed pulp. No significant variation in colour was observed during pressure treatment.     

Colour stability of canned strawberries using black carrot and elderberry juice concentrates as natural colourants

Besides texture degradation and aroma loss colour fading and browning of processed fruits, in particular strawberries, displaying comparatively low amounts of non-acylated anthocyanins, still pose a serious problem. Therefore, in the present study the colour of texture-improved canned strawberries was stabilised using commercial concentrates from black carrots and elderberries as natural colourants. CIE L ^* a ^* b ^* values of the fruit surface and of the brine solutions were monitored over a period of 24 weeks under light exposure. Furthermore, the contents of individual anthocyanins were analysed by HPLC-DAD. The colour of the processed control fruits (without added colourant) was unacceptable even at the beginning of the storage. Their anthocyanin contents were reduced by more than 85% at the end of the storage period. In contrast, the colour of canned strawberries containing black carrot and elderberry anthocyanins was significantly improved. Colour difference values ΔE ^* of black carrot-coloured strawberries were found to be smaller than those of the samples containing elderberry concentrate as a colourant. This could be ascribed to the presence of acylated anthocyanins in the first exhibiting exceptional storage stability, while all non-acylated pigments were degraded. The chill brining process for fruit firming markedly affected pigment stability, which can be attributed to enzymes that are still active at cold storage conditions.