Abstract
Recent growth and diversification of sheep milk products means more sophisticated methods are required to ensure their flavour quality. The objective of this study was to compare four extraction techniques for the analysis of volatile compounds in sheep milk by gas chromatography-mass spectrometry (GC-MS). Solvent Assisted Flavour Evaporation (SAFE), Solid Phase Microextraction (SPME), Headspace Sorptive Extraction (HSSE) and Stir Bar Sorptive Extraction (SBSE) were evaluated for their sensitivity, selectivity, reproducibility, and overall efficiency. A total of 48 volatile compounds from nine compound classes were identified in the spray-dried sheep milk. Alcohols, aldehydes, alkanes, carboxylic acids, ketones, lactones, sulphur compounds, nitrogen compounds, and terpenes were all present, but the differences between the methods were most apparent for lactones. SBSE extracted eight lactones, SAFE extracted four lactones and HSSE and SPME only detected trace levels of two lactones. Six of the lactones—δ-hexa-lactone, δ-octalactone, γ-decalactone, γ-dodecalactone, δ-tetradecalactone, and δ-hexadeca-lactone—were identified for the first time in spray-dried sheep milk. The present work demonstrated that SBSE is an effective tool for the extraction and analysis of volatiles, especially lactones, in sheep milk and dairy products in general. A discussion of the benefits and limitations of each method is included.
Highlights
Sheep milk, at around 1.5%, represents a relatively small proportion of global milk production, but its popularity has grown in recent decades [1]
The present work optimized and compared four volatile extraction techniques based on their respective benefits and biases
One of the major drawbacks of headspace techniques is that they tend to lack sensitivity for larger, less volatile compounds compared with liquid extraction techniques [30]
Summary
At around 1.5%, represents a relatively small proportion of global milk production, but its popularity has grown in recent decades [1]. From 1994 to 2013 global sheep milk production grew by 26%, led by dramatic increases in Africa and Asia [1]. A limited amount of literature has directly examined the volatile flavour compounds and the impact of processing on those compounds in sheep milk. Teng et al investigated the impact of seasonal variation, pasteurization, and spray-drying on the volatile branched chain fatty acids of New Zealand sheep milk [3]. The study found that there were seasonal effects and that spray-drying led to significantly higher levels of those fatty acids [3]. To the best of our knowledge, no studies have investigated the broader range of volatile compounds in spray-dried sheep milk or in
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
