The collaborative evaluation of a procedure for the determination of N-nitroso compounds as a group

Two collaborative studies have been made of the method devized for the determination of N-nitroso compounds as a group, which involves their selective denitrosation with hydrogen bromide in glacial acetic acid, followed by the measurement of the nitric oxide liberated using a chemiluminescence analyzer, such as the TEA. Considerable variation was evident between the results in the first study, most of the values reported being low. This situation undoubtedly arose from the carry-over of traces of hydrogen bromide from one determination to the next, which resulted in premature denitrosation. The precision and consistency of the results were greatly improved in the second study, for which additional precautions had been recommended. All of the six participating laboratories reported reasonably consistent values, the coefficients of variation being 27.9% and 21.1% respectively, at the levels of spiking of N-nitrososarcosine equivalent to 32.9 ng and 146.4 ng of nitric oxide.     

EFFECTS OF DIFFERENT SALT CONTENTS ON SOME QUALITY CHARACTERISTICS DURING PROCESSING OF DRY‐CURED TURKISH PASTIRMA

ABSTRACT

This study examined the effects of different salt contents (3, 6 and 9%) during process stages on physicochemical, lipid oxidation and microbial quality of a dry‐cured meat product, past?rma, throughout 21 days of processing. Significant changes in moisture content, NaCl content, pH and water activity (a_w) were observed in past?rma after the third drying and pasting stages. There were significant decreases (P < 0.05) in objective color characteristics (L*, a* and b*) between raw material and final product for all past?rma samples. However, no significant effect of salt level (P > 0.05) was detected on L* and a*. Salt level significantly (P < 0.05) affected thiobarbituric acid‐reactive substances (TBARS) formation, which was lower in low‐salt past?rma samples, while the combination of salting, drying and pressing stages increased TBARS values in high‐salt past?rma samples. Higher salt content (6% and 9%) and last drying resulted in reduction of microbial count.

PRACTICAL APPLICATIONS

Salt (NaCl) is an important agent in inhibiting microbial growth, reducing water activity and imparting a salty taste to dry‐cured meat products such as ham and past?rma. Salt content in past?rma varies from 5% to 10% in the final product and has an impact on product quality parameters. The effects of different NaCl contents (3, 6 and 9%) and processing stages on pH, water activity (a_w), color parameters, lipid oxidation and microbial count were studied during processing of past?rma. Low‐salt concentration had some negative impacts on past?rma characteristics, giving high a_w, pH and microbial count, but low Thiobarbituric acid‐reactive substances value and NaCl content. Drying, pressing and pasting with çemen mixture during past?rma processing had a positive impact on reduction of moisture, a_w and microbial count.

     

The transnitrosation of N-methylaniline by a protein-bound nitrite model system in relation to N-nitrosamine formation in cured meats

The reactions of sodium nitrite, S-nitrosocysteine hydrochloride, S-nitrosoglutathione and a ‘protein-bound nitrite’ model system with N-methylaniline at pH 5.5 and 37°C have been compared. The results show that the rate of nitrosamine formation from sodium nitrite and S-nitrosocysteine is greater than that from the model system although the latter depends upon the local concentration of nitrosothiol groups on the matrix. Transnitrosation by S-nitrosoglutathione is considerably slower than the other reactions. The implications of the results with respect to nitrosamine formation in cured meat are discussed.     

Synthesis of an ionic N-nitrosamine and a method for its determination in foodstuffs

Summary A model ionic N-nitrosamine (N-nitroso-N¹N¹-dimethylpiperazinium iodide) was synthesised in order to develop an appropriate analytical method for examining the possible incidence of this class of compounds in food. A procedure suitable for its analysis in biological samples is described and is based on preparation of an aqueous extract, ion-pair extraction into an organic solvent, separation by high-performance liquid chromatography and detection with a thermal-energy analyzer. The average recovery of the ionic N-nitrosamine from cured meat was 83% at 200 g/kg; the detection limit was 50 gm/kg. bei den Muskelproben nahezu 30% der mit Hilfe der

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Synthese eines Ionischen N-Nitrosamins und eine Methode für dessen Analyse in Lebensmitteln

Zusammenfassung Ein Modell eines ionischen N-Nitrosamins (N-Nitroso-N¹N¹-dimethylpiperaziniodid) wurde synthetisiert, um die entsprechende analytische Methode zur Prüfung des möglichen Auftretens von Verbindungen dieser Klasse in Lebensmitteln zu entwickeln. Es wird ein für die Analyse dieses Stoffes in biologischen Proben geeignetes Verfahren beschrieben, das auf der Zubereitung eines wäßrigen Extrakts, Ionenpaar-Extraktion in einem organischen Lösungsmittel, Trennung durch Hochleistungs-Flüssigkeitschromatographie und Nachweis mit Hilfe eines thermischen Energieanalysators beruht. Aus geräuchertem Fleisch mit einem Gehalt von 200 g ionischem N-Nitrosamin/kg wurden im Durchschnitt 83% des Stoffes extrahiert, die Methode hat eine Nachweisgrenze von 50 g/kg.

     

Comparison of health-relevant flavonoids in commonly consumed cranberry products

The human health benefits from consumption of cranberry products have been associated with the fruits' unique flavonoid composition, including a complex profile of anthocyanins and proanthocyanidins. However, when processed by techniques such as pressing, canning, concentrating, or drying, a number of these natural components may be compromised or inactivated due to physical separation, thermal degradation, or oxidation. Fresh cranberries were compared to freeze-dried berries and individual fruit tissues (skin and peeled fruit). Products examined included cranberry juices (commercial and prepared from concentrate), cranberry sauces (commercial and homemade), and sweetened-dried cranberries (commercial). Freeze-drying resulted in no detectable losses of anthocyanins or proanthocyanidins from cranberry fruits. Anthocyanins were localized in the skin. Proanthocyanins were higher in the skin than in the flesh, with the exception of procyanidin A-2 dimer which was concentrated in the flesh. Anthocyanins were significantly higher in not-from-concentrate juice than in reconstituted juice from concentrate (8.3 mg and 4.2 mg/100 mL, respectively). Similarly, proanthocyanidins were markedly higher in not-from-concentrate juice compared to juice from concentrate (23.0 mg and 8.9 mg/100 mL, respectively). Homemade sauce contained far higher anthocyanins and proanthocyanidins (15.9 and 87.9 mg/100 g, respectively) than canned sauces processed with whole berries (9.6 and 54.4 mg/100 g, respectively) or jelled-type (1.1 and 16 mg/100 g, respectively). Sweetened-dried cranberries were quite low in anthocyanins (7.9 mg/100 g), but they still retained considerable proanthocyanidins (64.2 mg/100 g). Commercially processed products contained significantly lower levels of polyphenols as compared to fresh and home-processed preparations. Anthocyanins were more sensitive to degradation than proanthocyanidins. Practical Application: As cranberry juices and other products are increasingly consumed for their recognized health benefits (including prophylaxis against urinary tract infection), it is relevant to consider how various degrees of commercial and home processing can alter innate levels of the biologically active flavonoids (especially anthocyanins and proanthocyanidins) characteristic to the intact fruits.