# Electronic Nose Analysis to Detect Milk Obtained from Pasture-Raised Goats
###### Abstract  
The nutritional peculiarities of dairy products made with milk from pasture-fed ruminants would require a rapid control to be authenticated and limit the risk of fraud. In the current study, ninety milk samples from two groups of goats were analysed by electronic nose, quantitative descriptive sensory (QDA) and gas chromatography-mass spectrometry analysis with the aim of discriminating between milk produced on grazing and on a confinement feeding system. The raw milk samples were taken at five different times over a period of three months (April, May and June, 2021) from eighteen individual Saanen goats divided into two groups, one of which was fed outdoors on a highly biodiverse pasture. Linear discriminant analysis (LDA), carried out on electronic nose data, was able to classify the two types of milk in terms of an animal feeding system (88% correct classification). Pasture milk scored higher for sensory descriptors such as \"Grassy\" and \"Sweet aromatic\" odours. Trepene compounds were the chemical class that qualitatively differentiates the pasture milk while volatile fatty acids were the most present quantitatively. Electronic nose has proven to be a rapid, reproducible and simple method for authenticating pasture raw milk in routine control analyses. E-nose; pattern recognition techniques; MOS sensors; small ruminants; raw milk; milk volatile organic compounds; milk authenticity; quality control; Noble milk; sensory analysis +
Footnote †: journal: Medical  
the use of silage and genetically modified feedstuffs in the livestock feeding system, the use of a high forage:concentrate ratio of at least 70:30 and, depending on the source of forage, it provides two different milk labels. In the \"Pasture\" milk, the animals must be fed for at least 150 days a year on a high biodiversity pasture. Instead, the \"Stall\" label contemplates the use of hay in an indoor animal diet [13; 14]. Consumers involved in the consumption of premium products have expressed that they can pay a higher price for the purchase of Noble milk from grazing ruminants [15]. However, the reputation as a premium product makes pasture-based dairy products vulnerable to fraud. This implies that the pasture-fed origin must be objectively and rapidly proven to protect consumers against potential frauds. Since the volatile compounds of milk are qualitatively and quantitatively influenced by the animal feeding regime [3; 16], their determination in raw milk could be a decisive analysis to be applied in the discrimination of milk produced by grazing animals compared to that produced by animals fed with conventional indoor diets. While volatile compounds analysis is time-consuming, costly and require skilled personnel, E-nose can be a useful portable device for a quick assessment of milk quality, rapidly evaluating complex and volatile gas mixtures in the sample headspace [17]. Schematically, E-nose is composed of an array of gas sensors with different selectivity, a signal-collecting unit and pattern recognition software. The use of the E-nose has involved different foods (fruits, alcoholic beverages, cooked and raw meat) and has been applied for different objectives [18; 19; 20; 21]. The applications of E-nose in the dairy sector (milk, yogurt and cheese) have recently been reviewed [22]. In fresh milk, E-nose has been used for several purposes such as monitoring microbial growth [23; 24], milk discrimination based on the farming system [17], identification of traces of detergent in milk [25; 26] and discrimination of milk from cows fed on two different Alpine pastures [27]. As far as we know, no information is available on the use of electronic nose as a useful device for authenticating raw milk from pasture-fed goats. Thus, in this study, we used an electronic nose consisting of ten metal oxide semiconductor (MOS) sensors to differentiate raw milk samples from grazing or confinement-fed goats and authenticate pasture milk.