No abstract

Selective ion flow tube mass spectrometry (SIFT-MS) is a direct mass spectrometric technique that allows qualitative and quantitative analysis of a large number of volatile organic compounds. Because of its speed and ease of use, this nondestructive technique could be considered as a practical tool for quality control. This research focuses on the possibilities of direct headspace sampling by SIFT-MS for the quantification of the volatile basic nitrogen content (TVB-N) of fish fillets. These volatile bases [trimethylamine (TMA), dimethylamine (DMA), and ammonia] give additional information in conjunction with the sensory scoring and microbiological analysis about the quality of the fish fillets. This research validates in a first part the SIFT-MS method for the quantification of the volatile bases in mixed cod samples. With regard to the investigated linearity, repeatability, reproducibility, recovery, limit of detection, and limit of quantification, SIFT-MS appeared to be an adequate technique for measuring volatile bases spiked on cod. In the second part of this research, the technique was validated for the analysis of volatile bases on cod fillets during a storage experiment under ice. A good correlation was obtained between the proposed direct headspace sampling and traditional methods. The sensitivity of the SIFT-MS method can be improved when cod fillets are made more alkaline (pH >11) during sampling.

The incorporation of active oxygen scavengers in polymer packaging materials is essential to allow packaging of oxidation sensitive products. Opposed to the currently available chemical oxygen scavengers, systems based upon natural and biological components could have advantages towards consumer perception and sustainability. A modelsystem for a new oxygen scavenging poly(ethylene terephthalate) (PET) bottle is proposed using an endospore-forming bacteria genus Bacillus amyloliquefaciens as the active ingredient. Spores were incorporated in poly(ethylene terephthalate, 1,4-cyclohexane dimethanol) (PETG), an amorphous PET copolymer having a considerable lower processing temperature and higher moisture absorption compared to PET. To asses spore viability after incorporation, a method was optimized to extract spores from PETG using a chloroform/water mixture. Samples were also analyzed using a Live/Dead BacLight Bacterial Viability kit. It was shown that endospores were able to survive incorporation in PETG at 210°C. Incorporated spores could actively consume oxygen for minimum 15 days, after an activation period of 1-2 days at 30°C under high humidity conditions. Industrial relevance: The study describes a modelsystem for the use of incorporated spores genus Bacillus amyloliquefaciens as an active oxygen scavenger in PET multilayer bottles using PETG as the middle layer material. Industrially, oxygen scavengers using incorporated viable spores as the active compound could have advantages towards consumer perception, recyclability, safety, material compatibility, production costs, … compared to currently available chemical oxygen scavengers.

No abstract

The growth-inhibiting effects of simple and commercial salt replacers on the growth of Listeria monocytogenes were determined in broth at 7C. The divalent chlorides, CaCl2 and MgCl2, had the largest antilisterial activities at equivalent water phase concentrations or molalities followed by NaCl ª KCl and MgSO4 in decreasing order of antilisterial effect. Additional antilisterial activities other than their water activity depressing effects were observed for CaCl2 and MgCl2. Challenge tests performed on cooked ham and white sauce showed that reduction of NaCl levels by Յ28 and 33%, respectively, did not affect the stability of these products to L. monocytogenes. It can be concluded from the study that changes in the stability to L. monocytogenes are most likely to occur when NaCl is fully reduced and/or replaced or partially replaced by either CaCl2 (increased stability) or MgSO4 (reduced stability).