GROWTH DYNAMICS OF INDIGENOUS MICROBIAL POPULATIONS ON VEGETABLES AFTER DECONTAMINATION AND DURING REFRIGERATED STORAGE

To ensure microbiological stability and safety in minimally processed (MP) salad vegetables, it is essential to consider the microbiology of this produce during cultivation and harvesting, and the potential changes to this microbiology through preparation, distribution and storage. This study takes two salad vegetables (lettuce and white cabbage) and, having enumerated a range of different physiological groups of microorganisms present on unwashed produce, determines the impact on each microbial group of applying a decontamination step in the preparation protocol. The disinfectant used was sodium dichloroisocyanurate. Decontamination reduced the total microbial load significantly on both vegetables. The levels of different microbial groups enumerated differed significantly between vegetables. All the microbial populations were reduced, but the biocidal effect of chlorine treatment varied with vegetable type. Reduction of the levels of lactic acid bacteria and aerobic psychrotrophs on cabbage was only achieved with inclusion of the decontamination step, and this effect, in general, did not last more than 3 days. Decontamination significantly reduced the levels of coliforms, and although the levels increased during refrigerated storage, they did not exceed initial levels found on unwashed produce. In addition, the levels found on treated cabbage remained lower than produce washed with water only.     

BIOGENIC AMINE CONTENT OF SOME TURKISH CHEESES

Biogenic amines in ten samples of Kaşar (aged), five samples of Kaşar (fresh), four samples of Mihaliç, nine samples of Van Otlu (herbed), nine samples of Örgü, nine samples of Urfa and six samples of Civil cheeses were obtained from local supermarkets of Ankara. Tryptamine (TRY), phenylethylamine (PHA), putrescine (PUT), cadaverine (CAD), histamine (HIT), tyramine (TYA), spermine (SPM) and spermidine (SPD) contents of Turkish cheese samples were screened by high performance liquid chromatography (HPLC).
PUT, CAD, HIT, TYA and SPD were the predominant biogenic amines in maturated Kaşar (aged), vacuum-packed Kaşar (fresh), Mihaliç, Otlu (herbed) and Örgü cheeses. PHA, CAD, TYA and SPD were the predominant biogenic amines in Urfa cheese samples.
Civil cheeses were found to contain the highest HIT and TYA content with an average of 94.76 mg/100 g and 138.16 mg/100 g, respectively, much higher than the toxic dose. HIT level of Mihaliç cheeses were also higher than the accepted limit. The concentration of amines in all other cheeses was much lower than the toxic dose limits.     

CHANGES IN BIOGENIC AMINE CONTENTS AND SENSORY QUALITY OF SARDINE (SARDINA PILCHARDUS) STORED AT 4C AND 20C

Biogenic amines (tyramine, putrescine, cadaverine, histamine, spermidine and spermine) in sardine during the storage at two temperatures (4C and 20C) were investigated. Changes in sensory scores were also recorded. Significant differences between storage times were found. The levels of tyramine, putrescine, cadaverine and histamine increased as decomposition of sardine progressed at both 4C and 20C. Spermidine and spermine did not change throughout storage. Putrescine was the main biogenic amine formed, followed by tyramine, cadaverine and histamine. Histamine remained lower than the toxic level of 100 mg/kg in the samples stored at 4C whereas it exceeded the toxic level after 16 h at 20C. The increase in histamine concentration was lower than tyramine and putrescine at both temperatures. Sensory scores gradually decreased during the storage.     

CHANGES IN BIOGENIC AMINES OF MAJOR PORTUGUESE BLUEFISH SPECIES DURING STORAGE AT DIFFERENT TEMPERATURES

Changes in histamine (Him), cadaverine (Cad), putrescine (Put), agmantine (Agm) and volatile basic nitrogen (VBN) contents were examined in sardine, Atlantic horse mackerel, chub mackerel and Atlantic mackerel, during ice storage and storage at room temperature. Him formation as well as other amines varied greatly with species of fish and storage conditions. The levels of Him, Cad, Put and VBN increased gradually in all the fish species as decomposition progressed, regardless of storage temperatures. In iced fish, amine production was considerably reduced and Him concentration was, in general, lower than 100 mg/Kg. During ice storage amines increased slowly until day 7, after which a significant rise was detected. In comparison with the other fish species higher levels of Him, Cad and Put were determined in Atlantic mackerel. At room temperature Him, Cad and Put were produced at the highest concentrations in chub mackerel, followed by sardine, Atlantic mackerel and Atlantic horse mackerel. Him concentration maximum exceeded allowable limits for human consumption in the first three species after 24h of storage at room temperature. No correlation was observed for Him or other amine levels and the degree of fish decomposition. Thus, the use of Him or other amines as a freshness index of the studied fish species was not considered appropriate.     

FORMATIONS OF BIOGENIC AMINES IN TURKISH STYLE SAUSAGE DURING RIPENING AND STORAGE PERIODS

Changes of biogenic amine (histamine, β‐phenylethylamine, serotonin, spermine, spermidine, cadaverine, putresine, 1,7‐diamino heptane, tryptamine and tyramine) concentrations and pH values of Turkish style sausages were investigated during ripening and storage. Cadaverine and β‐phenylethylamine were not detected during the ripening and storage periods for all sausage types. Storage time had a significant (P<0.05) effect on the formation of all biogenic amines. Starter culture usage decreased (P<0.05) biogenic amine formation. Histamine levels were higher in sausages prepared without additives and lower in the sausages made with starter culture than the sausages made without starter culture. There was no effect of starter culture and additives on formation of tryptamine, 1,7‐diamino heptane, serotonin or spermidine. Starter culture and additives affected (P<0.05) the formation histamine, putrescine and spermine. pH values of sausages sharply decreased (P< 0.05) from 5.98 to about 4.53 during 3 days of ripening. After that, pH values increased slowly and were nearly constant during the storage period.     

THE STORAGE LIFE OF FRUITS AND VEGETABLES

Exponential curves have been fitted to published temperature/time/quality data for both fresh and frozen fruits and vegetables. The two constants in the exponential equation are used as measures of the relative storage life of the product and of its sensitivity to temperature change. Of these 2 constants, 1 is analogous to the “Q₁₀” value often used to express temperature sensitivity, but it is independent of actual temperature. The two constants are used to provide an index of “storability” of different fruits and vegetables and a tentative classification of produce according to this “storability” is presented. Fitting curves to temperature/time/quality data also allows prediction of the effects on storage life of fluctuating product temperatures, such as are experienced during normal transport and storage.     

A STUDY OF THE EFFECT OF STORAGE AT 5°C ON THE MICROBIAL FLORA OF HEAT-TREATED MARKET CREAM

Changes in the microbial flora of heat-treated cream due to storage at 5°C for five days were studied. The relatively mixed flora of fresh cream at both 5°C and 30°C incubation temperatures appeared to vary according to source, with few psychotrophic organisms originally. After storage the flora became almost dominated by psychotrophic types with total numbers not less than 10⁶/ml, although the original numbers were very low indeed—in most samples less than 1500/ml.     

INTERACTION BETWEEN TRIOLEIN AND NATURAL HAKE ACTOMYOSIN DURING FROZEN STORAGE AT -18C

The interaction of hake muscle actomyosin with triolein in 0.6 M KCl, pH 7, during frozen storage has been investigated. ATPase activity, protein solubility and relative viscosity measurements were performed. No effect of triolein on these functional properties was observed during the storage period studied. Incorporation of l-14C triolein to the protein was found over the storage period, indicating that despite the lack of effect on functionality, lipid-protein interaction occurs. No differences were found in the electrophoretic patterns between control and neutral lipid added samples.