Origin of animals

The origin of C. porcellus (n=15) was from backyard production systems, located in the Metropolitan Area of Mexico City. Next, we mention some zootechnical aspects of the guinea pigs used: the breed was American; the pups had a lactation period of 18 days; after weaning, the males were selected and a homogeneous lotification was carried out based on weight, so that good growth and development could take place. The time from weaning to slaughter was 5 ± 0.7 months of age and they obtained a live weight of 700 ± 62 g. The rearing of these animals was carried out with a mixed diet [vegetable waste (70 %) and commercial concentrate for rabbits (30 %)], and the health and safety in the primary production of guinea pig meat was guaranteed.

Descripción de la ración alimenticia Description of the food ration

In the feeding system, commercial concentrated feed was used (14.5% crude protein) and organic waste from CEDA (non-conventional) was integrated. Table 1 shows the nutritional values of the non-conventional foods used in this study, which were previously evaluated and reported by our work team (^{Almaráz et al., 2012}). With these data, the nutritional requirements recommended by Xicohtencatl et al. (2013).

Obtaining the guinea pig carcass

The sacrifice was carried out following the animal welfare protocols, desensitization was by exposure to 90% CO2, for 17 min (^{AVMA, 2020}), and at the end of this time a cross-section was made in the jugular vein to bleed. Subsequently, the carcasses were placed in the caudo-cranial position to proceed to slaughter (skinned and gutted) (^{Mota-Rojas et al., 2012}) and then the carcasses (417 g ± 60) were stored at 4 °C for 24 h (^{Rubio et al., 2014}); then each channel was separated according to the protocol of ^{Sánchez-Macías et al. (2016)}, separating and identifying the portion of the long leg. Finally, the samples were placed at -20 °C(^{Rodbotten, 2004}), for later use in sensory tests.

Sample preparation

A slow thawing protocol was followed (24 h period), until an internal temperature of 5 °C was obtained in the samples (^{Font, 2006}), and then the connective tissue and covering fat were removed.

Consumer characteristics and sensory testing

The gastronomic proposal was presented to the judges-consumers, in a context of consumption as close to reality as possible, the basic criterion was to simulate the conditions of ‘Gastronomic Experience’ in the most reliable way possible. Despite the above, the area where the evaluation was carried out allowed control, such as lighting (white light), temperature (25 °C), noise and strange odors. The evaluation time was at 11:00 am (after breakfast and before lunch.

This gastronomic proposal consisted of four stews with guinea pig meat (in mushroom cream, roast, sweet and sour marinated and in yellow mole). The stews were made with ingredients commonly used in Mexico (Table 1), and 2 cooking systems were used; two of these analyzed in a preliminary study by this research group (^{Luna et al., 2017}). For each of the techniques, an internal temperature of 75 °C (in the geometric center) was obtained in the meat.

Forty consumers of both sexes were recruited, with an age range of 20 to 52 years, which indicated that they were habitual consumers of meat; they were also informed of the type of meat to evaluate. For the acceptance test, each consumer was presented with the four dishes (at 55 °C) plated (in 4 times and in plain white dishes) and they were provided with water as a cleaning agent for taste, which they used before cooking evaluation of each stew (^{Peachey, 2002}).

The affective methodology was used (^{González et al., 2017}) with a structured 7-point hedonic satisfaction scale (I dislike it a lot: -3; I dislike it moderately: -2; I dislike it: -1; I neither dislike it nor do I like it: 0; I like it: 1; I like it moderately: 2 and I like it a lot: 3). The sensory variables evaluated were tenderness, juiciness, taste and smell.

Statistical analysis

XLSTAT-Sensory software version 2015.6.01.25740 (Copyright Addinsoft 1995-2016) was used. For the acceptance study, a group of consumers was carried out that generated the types for the global appreciation variable associated with the four attributes evaluated in the sensory test. That is, an Ascending Hierarchical Classification (AHC) and a Principal Component Analysis (PCA) of the sensory attributes were used to build the quadratic model of external preferences mapping (EPM) (^{González et al., 2017}).

Study of the acceptance of guinea pig meat

Sensory analysis can be a good tool to develop new products in a restaurant, by simulating the conditions in which this meat can be offered; the proposal allowed to evaluate their perception in a realistic situation. In the sensory space (Figure 1), the sensory attributes that are associated with the first main component (F1) are smell, taste and tenderness and the attribute associated with the second component (F2) was juiciness and represented 90.99 % of the variability of the acceptance data. Consumers were found to have different perceptions of attributes; the above, due to the culinary technique and the ingredients used.

Figure 1 Sensory space of the gastronomic proposal with Cavia porcellus meat. Sensory attributes were rated using a 7-point hedonic acceptance scale 

The most widely accepted proposal was the guinea pig prepared in cream of mushrooms, locating in the positive values for both main components and in particular in the preference associated with the flavor attribute as it is stronger, since it moves away from the direction indicated by the vector. The roasted guinea pig obtained positive values for smell, flavor and tenderness, but negative for juiciness. Therefore, this culinary preparation was less accepted. The external preference map (Figure 2 and 3) indicates that for type 2 consumers, there is a significant effect (R²=0.976, p <0.05); since this model explained the preferences of this group of consumers, determining their general acceptance in common for guinea pig in cream of mushrooms. Type 1 and type 3 have R² = 0.968 and R²=0.893 (p <0.05) which determines their general acceptance in common by guinea pig in yellow mole and in cream of mushroom cream respectively.

Figure 2 External map of vector model preference for the general acceptance of Cavia porcellus meat, rated using a 7-point hedonic acceptance scale. 

Figure 3 Preference map and contour graph of satisfaction percentages using a vector model for general acceptance for Cavia porcellus meat, rated using a 7-point hedonic acceptance scale. 

For consumers belonging to types 4 (R²=0.081), the model applied in the present investigation could not explain the preferences. Type 2 and type 3 show similar preferences for guinea pig in cream of mushrooms, since this stew is the most preferred in both types. The percentage of satisfied consumers (Figure 3) was 60-80 % for guinea pig stews in mushroom cream, yellow mole and bittersweet marinade and 40-60 % for roast guinea pig.

^{Barham et al. (2010)} indicated that the judgment of the quality of a stew is a personal matter, such as the extent to which a particular meal is enjoyed or not, and that a series of conditions must be met (taste, texture, juiciness and smell), before the food is really nice. In the present work, despite the use of different culinary techniques for the preparation of these stews, the sensory scores of the structured hedonic scale (bipolar) place them in positive values, which indicates that the consumer accepted this type of meat in different presentations. When elucidating the conditions for which the stews were described by this group of individuals under study as pleasant, it is worth mentioning the way in which they were able to meet the conditions for it; and it was through the production of raw materials (which was the same for all the stews), in the cooking process (different culinary techniques) and in the way food is presented (variable ingredients); of course, with the preparation of the stews (ingredients and their combination). In addition to the cooking process carried out in a proper way, it can lead to the quality development of a food dish. In some stews, processes that developed the flavor were involved, as observed in guinea pig in cream of mushrooms, which obtain positive ratings for flavor and in others this can affect the organoleptic characteristics, as happened with the roast that was the least accepted and obtained negative ratings on juiciness.

^{Natividad et al. (2010)} and ^{Flores-Mancheno et al. (2017)} elaborated sausages with guinea pig meat reporting good organoleptic characteristics and ^{Apráez (2011}), obtained acceptance for guinea pig chorizo in 21.67 % with significant differences for the category 'I like it very much', for the guinea pig chorizo . Other sensory evaluations have also been carried out for C. porcellus meat, in different presentations, and smoked guinea pig meat was the most widely accepted, followed by breaded guinea pig meat and croquettes (^{Argote et al., 2009}).

Also, ^{Argote et al., (2009)}, using a quantitative model and random probability sampling, collected information on the preference for guinea pig meat in Colombia (traditionally consuming beef), finding that 96 % of the surveyed population has consumed meat from guinea pig, and the rest (4 %) do not do it because they do not like its taste and appearance. Therefore, the incorporation of this type of food is viable, since the results obtained in the hedonic scale for the different dishes are classified as: I like it, I like it moderately and I like it a lot.

In a similar way to the present study, ^{Yaguache (2013)} proposed culinary alternatives using guinea pig meat and evaluated them sensually using a hedonic scale; the prepared dishes were well accepted. 45 %, 46 %, 54 % and 44 % of consumers indicated that they really liked the guinea pig skewers, pork rinds, guinea pig wrap, and guinea pig in wine, respectively. Therefore, it was reported that guinea pig meat is liked by all palates in different ways of preparing it. The guinea pig is gaining importance as a source of exotic meat, and consequently its importance as a meat-producing animal is increasing; but there is still research on its meat quality traits and it needs to be explored in greater depth. However, in subsequent studies it is important to use the C. porcellus species adapted in Mexico and not to consider moving native animals from South America, since as suggested by ^{FAO (2010)}, «biological diversity has an intrinsic value and must preserve itself at the highest possible level».

The acquisition of this meat may be viable, as indicated by ^{Xicohtencatl et al. (2013)} who indicate a production cost of a guinea pig at weaning of $ 30.14 pesos MN and infer that guinea pig production systems can have income from the sale of guinea pigs for pets and also from the production of meat for local consumption.