Spadafora N.D.,University of Cardiff |
Machado I.,Catholic University of Portugal |
Muller C.T.,University of Cardiff |
Pintado M.,Catholic University of Portugal |
And 2 more authors.
Melons are an important component of fresh fruit salads, however, they suffer from limited shelf life. Processing of melon fruit for use in fruit salads induces a number of changes including alterations in colour and texture. In addition, respiration rate and ethylene production are affected. Processing also elicits changes in flavour (sweetness) and aroma (production of volatile organic compounds - VOCs), of critical importance to the consumer. Several parameters govern shelf life; temperature is a critical factor. In this study we tested whether cut size is another parameter that can affect quality indicators. Melon (Cucumis melo 'Arapaho') cubes of three sizes were stored at 4°C and assessed for quality at five time-points over a 15-day period. We assessed a number of parameters including firmness, loss of fresh weight, respiration rate, antioxidant capacity, phenolic compounds and carotenoid content. In addition we measured VOC profiles to assess whether there were any qualitative changes associated with storage period and/or cut size. Fresh weight (FW) loss and respiration rate increased significantly with storage time and FW loss was affected by cut size. Total carotenoid levels remained stable during the storage time as did antioxidant capacity in all cut sizes. However, cinnamic acid levels tended to decrease in the last stage of the storage period and changes in β-carotene content correlated with cut size (though not significantly). We were also able to separate the VOC profiles from the different cut sizes indicating that VOCs may be useful markers as indicators of the effects of cut size and storage time on quality. Source
Watson N.M.,Markes International Inc.
Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA
The series 2 UNITY-Air Server™, a new, cost-effective system for round-the-clock speciated measurement of multiple trace-level VOC in air or pure gases was presented. The system was validated for on-line monitoring of the 27 ozone precursors specified by European regulators, including ethane, ethylene, toluene, n-butane, o-, m-, p-xylene, and isoprene. A reliable, semi-continuous, cryogen free sampling and GC/FID analysis system has been demonstrated for this challenging and complex mix of volatile and very volatile hydrocarbons. The design of the focusing trap and the sorbent choice within increased the maximum sample volume and along with the complete transfer of the whole sample to the GC system, allowing for greater sensitivity. Reliability and stability of the system was excellent, achieving < 0.3% RSD in retention time shift and > 98% of compounds having linearity of ≥ 0.99. This is an abstract of a paper presented at the 104th AWMA Annual Conference and Exhibition 2011 (Orlando, FL 6/21-24/2011). Source
Barden D.,Markes International Inc.
The detection of volatile organic compounds (VOC) is important for a variety of reasons, many of which stem either from the need to ensure that damaging chemicals are controlled or eliminated, or the desire to understand more about the chemicals that affect the enjoyment of the world around. These applications range from environmental monitoring to material emissions testing, but one area in particular has recently seen large advances-the analysis of VOCs in food. The large number of compounds released from food and the need to separate and identify them presents a particular challenge for the analyst, and one that demands techniques with the ability to identify the widest possible range of compounds from a single sample. In this respect, sulfur compounds appear often in the literature, primarily because of their disproportionately strong odors, even at trace levels. They are often of key importance in food aromas, although not only as indicators of decay, since they can be contributors to the distinctive aromas of certain foods. Source
Watson N.M.,Markes International Inc.
Air and Waste Management Association - Air Quality Measurement Methods and Technology Conference 2012
These examples have shown how recent advances in air monitoring technology have extended the range and robustness of GC-based analytical procedures for air samples collected using either canisters or sorbent tubes. Some of the potential applications and advantages that have been explored here, include automated screening of uncharacterized canister samples, reliable detection of very low-concentration species and technologies to facilitate transition from canisters to sorbent tubes, with the employment of simple grab sampling devices. With the advancement of air sampling techniques and technology excellent linearity and detection methods are available to ensure laboratory inaccuracies are minimized. The greatest area for inaccuracy when making ambient air measurements now lies with the sample collection itself. This paper has discussed the two main sampling types for VOC collection, canister sampling and absorbent tube sampling and it is important to ensure that when taking the sample the correct collection method is employed. These new technologies lend themselves to sampling smaller air volumes on to sorbent tubes, which can dispel user worries about breakthrough volumes and humidity effects. Taking small sample volumes and combining this with powerful detection techniques, such as time-of-flight mass spectrometry, allows detection of trace compounds to be achieved either at the same level or at much lower limits of detection when compared to less sensitive detection techniques. However, more work is required to identify the limits of new time-of-flight mass spectrometer technologies when used in combination with TD-GC systems for real-world air monitoring. Source
Widdowson C.,Markes International Inc.
12th International Conference on Indoor Air Quality and Climate 2011
New 'green chemistry' regulations and increased consumer awareness of product safety issues are driving global demand to test intentional and unintentional release (emission) of chemicals from everyday products. The new EC Construction Product Regulation (CPR), REACH and new US building codes are key examples of regulatory developments which will increase the need for chemical emissions testing as part of product labelling. Reference methods require chemical emissions from representative samples to be tested under simulated real-world conditions using small chambers or emission test cells. The method is carried out at a prescribed, near-ambient temperature and under a flow of pure, humidified air. Volatile and semi-volatile organic chemicals emitted by the sample pass into the chamber/cell air and are collected at specific times - typically 3, 10 or 28 days - using sorbent tubes. DNPH cartridges with HPLC analysis are also used for formaldehyde tests. This paper describes innovative new technologies to simplify the chemical emission testing and data analysis process. Source