The a large number of molecules mostly volatiles, produced

 

The shelf life extension of food products represents one of the biggest
challenges in the food industry. Indeed, the growing awareness of consumers
about the dangers of food poisoning accompanied by a willingness to hold fresh
products of higher quality, led to the development of active and intelligent
packagings whose goal is to slow down the deterioration processes affecting
both the safety and the nutritional and organoleptic quality of foods.

Among the organoleptic properties characterizing
specific cheese varieties, flavour is one of the most important, determining the
quality and the consumer’s acceptance of cheese 1…. The aroma of most
cheeses results from the combination of a large number of molecules mostly
volatiles, produced by complex microbial and biochemical transformations throughout
manufacture, ripening and deterioration processes 2, 14….  Free fatty acids, in particular short-chain and medium-chain fatty acids (SCFFAs and MCFFAs) play
a major role in cheese flavor by their abundance in the volatile fraction 3…
and their specific odor notes. They are mainly produced during cheese
maturation and storage from the hydrolysis of milk triglycerides by microorganisms
and native milk lipolytic enzymes 6, 7, 9…. FFAs are characterized by a rancid and unpleasant
odour note and can be involved either in cheese aroma or in a
rancidity defect when they are present in very important amounts 3, 4…. Thus, SCFFAs and MCFFAs
analysis can play an important role in evaluating dairy product quality. 

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During
the storage, deleterious changes occur in cheese including accumulation of
molecules which could be hazardous to health, loss of nutrient value and
development of off-flavours 10…. These changes, which have an important impact
on the shelf life of cheese result from diverse physical-chemical and
microbiological reactions among which lipid oxidation. The latter constitute a
significant process in cheese deterioration due to their important content in
lipids. The oxidation of lipids, principally of unsaturated fatty acids produces
many volatile secondary compounds like aldehydes and ketones 11…. Hexanal is considerated as the major volatile
odour-active carbonyl compound generated from lipid peroxidation and
represents a sensitive and useful chemical indicator to monitor the shelf life
of food 11, 12….

The
volatile profile of different types of foodstuffs,
including cheeses has
been extensively studied employing gas chromatography coupled to mass spectrometry
(GC-MS). This analytical technique which allows to identify
and quantify volatile compounds, requires a prior step of extraction that can be conveniently performed by headspace solid phase micro-extraction (HS-SPME).
The efficiency of SPME can be improved by using salting-out agent to increase
the amount of volatile analytes in the HS 24… and by choosing the
proper fiber coating with a good absorbance for the monitored compounds. 

Many research works have focused on
the quantitative determination either
of FFAs or hexanal in dairy products using GC-MS but none of these previous
studies has examined concomitantly the content evolution of SCFFAs, MCFFAs and
hexanal as shelf life markers in cheese.

Therefore, the
present study aimed to set up a GC-MS quantitative method to monitor these chemical markers and on the same
occasion, to optimize the HS-SPME conditions in order to improve their
extraction. This analytical method has been used to evaluate the efficiency of
a new active multilayer packaging in term of cheese shelf life extension by monitoring
the quantitative evolution of these specific markers over a long-term
experiment.   

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