Quantification of volatile compounds (oxidative and olfactory) in meat products and impact of seaweed addition on the sensory and volatile profiles of processed meat products

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Garicano Vilar, Elena
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University College Cork
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Now more than ever consumers demand healthier food options, including meat products, with ‘clean-label’, sustainable and natural ingredients without compromising their sensory experience; hence a greater need for innovative concepts and approaches towards new product development is required. In this regard, seaweeds compose a credible source of functional ingredients with bioactive properties. There is a positive association between processed meat consumption and the risk of chronic diseases, such as cardiovascular disease, certain cancers or type II diabetes, due to their high levels of saturated fats and sodium. Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation (i.e., frankfurters, ham, and canned meat). The optimization of processed meat products through the reduction of fat and the partial replacement of salt could potentially offset the risk. However, the influence of matrix changes on the character aroma compounds and sensory perception of the developed products could adversely affect consumer acceptability. Therefore, this research aims to characterize the volatile organic compounds (VOC) and aroma profiles of processed meat products and seaweed, and to study seaweed-based processed meat products in terms of shelf life and consumer perception. This thesis has demonstrated the feasibility of generating valuable VOC and aroma profiles of processed meat products and seaweed using sophisticated extraction, separation, and identification gas chromatography mass spectrometry techniques (GC-MS); and of developing a novel method using headspace high capacity sorptive (HiSorb) extraction for quantification of target lipid oxidation compounds. This in-depth approach provides information on the sensory characteristics and shelf life of the processed meat products (frankfurters and beef patties), following reformulation and/or storage. The work in this thesis primarily employed HiSorb and thermal desorption (TD) GC-MS (HiSorb TD GC-MS) with polydimethylsiloxane (PDMS) probes and headspace solid phase microextraction GC-MS (HS-SPME GC-MS) for VOC profiling, but also the use of gas-chromatography olfactrometry (GC-O) applications. Chapter 1 provides an updated insight into the main extraction/concentration techniques that are available for the determination of the main odour-active volatiles in beef and pork. Aroma compounds are challenging to extract, concentrate, separate, identify and quantify due to the complexity of meat. The review highlights the potential pros and cons of the main approaches used to date but also, how advances in extraction, chromatography and olfactometry helps elucidate more key aroma compounds. However, many VOC have been identified in beef and pork to date. It is the use of GC-MS and olfactometry methodologies that enable us to increase our knowledge of the importance of the key volatiles impacting on consumer perception, either positively or negatively. The review in chapter 2 provided insights into the volatile analyses of six commercially important brown and red seaweed species used in the food industry and highlighted the need for more information regarding VOC in edible macroalgae and to identify those most likely to impact sensory perception. This is as important for those VOC that positively or negatively contribute to sensory perception. Such information could be used to aid new product development or widen applications of these seaweeds in the food sector, one of which is in meat product formulation. In that regard, chapter 3 investigated the volatile profiles of dried brown (Himanthalia elongata, Undaria pinnatifida, Alaria esculenta) and red (Porphyra umbilicalis, Palmaria palmata) seaweeds, and a brown seaweed extract (fucoxanthin) from Laminaria japonica, some of which had not previously been described. A chemometric approach was used to collate data from GC-MS, direct sensory aroma evaluation, and GC-O to obtain a better understanding of their volatile profile and sensory perception. Once the volatile profiles of the seaweed were characterized, chapter 4 investigated the impact of the inclusion of four selected seaweeds (1 % w/w) in reformulated frankfurters in which salt addition was reduced by 50 % compared to a control. The overall acceptability of reformulated frankfurters containing seaweed was greatly influenced by the type of added seaweed (also linked to dosage), but overall, the addition of seaweed enabled salt reduction and thus improved the nutritional quality. Further processing of seaweed prior to addition, optimization of dose rates, combinations of seaweeds and/or highlighting potential nutritional benefits will be necessary before such products are accepted by consumers unfamiliar with seaweeds in their diet. Lipids may cause both desirable and undesirable flavours and aromas in meat. However, progressive lipid oxidation adversely affects meat quality. Sophisticated techniques such as GC-MS can be used to identify and quantify individual VOC associated with lipid oxidation. Hence, the aim in chapter 5 was to develop a GC-MS method using HiSorb extraction for untargeted volatile profiling and to quantify targeted LOC in raw beef patties over refrigerated storage. Using this approach to determine the concentrations of VOC associated with lipid oxidation that adversely impact sensory perception provided insights into the production parameters that could maximise the oxidative shelf life stability and quality of meat products. It is essential to expand the knowledge on how to protect foods against lipid oxidation. Synthetic antioxidants have been used for many years to retard lipid oxidation in foods. However, there is growing interest in replacing synthetic antioxidants with natural ingredients. Seaweeds are not only a valuable source of bioactive compounds and a good salt content replacer, but also exhibit extraordinary antioxidant potential which can be harnessed for a broad variety of food applications. Therefore, the validated HiSorb GC-MS method outlined in chapter 5 was applied to profile the aroma of raw beef patties reformulated with seaweed, packed in MAP, and stored under refrigeration conditions in chapter 6. The method was combined with GC-O to detect VOC changes that could cause off-flavours in the product over time, along with changes in colour and TBARS values indicative of lipid oxidation. The antioxidant activity of the seaweed was also examined in an attempt to evaluate their effect against product deterioration. The antioxidant activity present in seaweed, attributable to polyphenols, flavonoids and other antioxidants, opens new possibilities of application of these in fresh meat products. Their use could potentially increase shelf life of food products due to their antioxidant capacity, and replace artificial food additives.
Gas chromatography-mass spectrometry , Thermal desorption , High capacity sorptive extraction , Volatile organic compounds , Flavour , Odour , Sensory analysis , Seaweed , Processed meat products , Gas chromatography-mass spectrometry olfactometry
Garicano Vilar, E. 2022. Quantification of volatile compounds (oxidative and olfactory) in meat products and impact of seaweed addition on the sensory and volatile profiles of processed meat products. PhD Thesis, University College Cork.