Introduction

Humans have been eating insects since prehistoric times [1] and, to a greater or lesser extent, this has occurred in most cultures [2]. Thus, in the 21st century, around two million people worldwide consume insects as part of their diet, mainly in regions of Asia, Africa, and Latin America [3].

In Mexico, approximately 549 species of insects are incorporated into culinary traditions [4]. In addition, approximately 85 species of edible insects have been identified in Oaxaca, Mexico [5]. One of these species, Sphenarium purpurascens (Charpentier, 1845), is particularly significant in the state’s culinary heritage and is commonly referred to as the “chapulin” [6].

In Oaxaca, the harvesting of S. purpurascens traditionally begins with the June rains and lasts until December. It is mainly carried out in alfalfa pastures (Medicago sativa) and cornfields (Mesoamerican polyculture centered around Zea mays). However, the expansion of urban land has led to less local harvesting and more importation of the insect [6]. Thus, most of the S. purpurascens sold commercially comes from the Mexican states of Puebla and Tlaxcala, although a minority still comes from the Central Valleys region of Oaxaca [6]. Under these circumstances, the price per gram of protein from S. purpurascens is higher than that of eggs, meat, and dairy products [7], and 30% of the supply is perennial [6].

In nutritional terms, S. purpurascens contains between 50–75% protein and 6–11% fat [8]. Its fiber content has been reported to range from 3.9% to 32.2% [9–12], and S. purpurascens raised on a corn diet contains 20–25% less fiber than those fed alfalfa [11] or soybean [12] diets.

As for the fatty acid profile, S. purpurascens has been analyzed in only two studies, which identify 20% [12] and 69% [10] of polyunsaturated fatty acids, a difference that could be due to the insect’s diet [9]. However, only one of the studies specifies the diet of S. purpurascens and how, depending on whether it is based on corn or soy, it significantly changes the fatty acid profile and the ω-6:ω-3 ratio [12].

Furthermore, S. purpurascens is a functional food, a classification attributed to its fiber and polyunsaturated fatty acid content. These biomolecules, in addition to their nutritional value, have the capacity to modulate one or more metabolic processes that contribute to the promotion of health [13]. The fiber is primarily composed of chitin, a substance found in the exoskeleton of the insect [14, 15]. Insoluble chitin has been shown to assist in the treatment of constipation [16], possess anti-inflammatory properties [17], and promotes colonic eubiosis [17]. Conversely, polyunsaturated fatty acids have demonstrated the capacity to mitigate the risk of disorders and diseases associated with inflammatory processes, including cardiovascular disease [18].

However, despite the existence of nutritional composition analyses, no study has examined the contribution of S. purpurascens to the human diet under real culinary processing conditions or the amount ingested by consumers. Thus, there is a research gap regarding its effectiveness as a functional food since effectiveness is the extent to which a treatment works under real-world conditions [19].

It is imperative to address the issue of culinary processing, as it invariably results in a modification of the nutritional value of foods [20]. In the case of S. purpurascens, the physical and chemical factors intrinsic to cooking have the potential to influence the oxidative stability of polyunsaturated fatty acids [18].

The other significant condition that may influence the effectiveness of S. purpurascens as a functional food is the amount ingested, given that the favorable effect of a functional food is contingent not only on its bioactive compounds but also on the dose-response curve according to the physiological context of the consumer [21].

Indeed, although the therapeutic efficacy of bioactive components such as ω-3 fatty acids [22] and fiber [17] is well known, their effectiveness as components of S. purpurascens cooked and consumed in normal quantities in real-life contexts is unknown. Thus, the aim of this report is to explore the potential contribution of ω-3 fatty acids and fiber from traditionally cooked adult S. purpurascens to the diet of consumers in the Sierra Sur region of Oaxaca.

Materials and methods

This is a two-phase exploratory study. The first phase examined the nutritional content of S. purpurascens available at the weekly traveling market in the city of Miahuatlán de Porfirio Díaz (CMPD), located in the Sierra Sur region of the Mexican state of Oaxaca. The second phase determined the quantity and frequency of consumption of S. purpurascens among adults who purchase this food at the market. This report is part of a research project approved by the Research Ethics Committee of the Universidad de la Sierra Sur under number CEI-02 and registration number SPN/02/25042019.

Results

According to the testimony of the vendor interviewed who provided the samples of S. purpurascens that were analyzed, the origin of these samples was the municipality of Ocotlán de Morelos (16.79151° N, 96.67455° W, and an altitude of 1,644 meters based on WGS84), Oaxaca, where this insect is a pest of green alfalfa pastures and cornfields; however, the organized social response to control it is sustainable extraction. This is mainly done with nets and occasionally by hand, by people who collect, purge (store the insects in plastic bags for 24 hours), and sell the raw insects wholesale by the sack.

The vendor interviewed said that he buys the insect in bulk and cooks it at home. Culinary processing consists of placing S. purpurascens in a pot with previously boiled water, washing them, and draining them manually to remove impurities (soil, plants, and others). They are then poached (70°C–85°C) for 10–12 minutes. Once drained using a manual strainer, cooking continues on a griddle over low heat (around 90°C) for one hour, stirring and mixing the food constantly with a wooden spoon (to avoid damaging the insects). At the 45-minute mark, garlic blended with lemon juice is added, along with salt to taste.

Among the results of the proximate analysis, it is noteworthy that alfalfa-fed adult insects cooked as described contain on average 6.4 times more dietary fiber than those that were corn-fed, and this difference is not attributable to chance (Table 2). In contrast, differences in other nutritional parameters are attributable to chance, due to the bilateral nature of the CI and the t-test results.

The proportions of fatty acids are similar in both types of S. purpurascens (Table 3). They provide fewer a lower proportion of ω-6 polyunsaturated fatty acids (linoleic C18:2) and a higher proportion of ω-3 polyunsaturated fatty acids (linolenic C18:3 n-3). The latter is the most deficient in the diets of modern industrial societies, which are characterized by a pro-inflammatory imbalance associated with a higher proportion of ω-6 [29]. Thus, ingesting S. purpurascens could contribute to balancing the ω-6:ω-3 ratio, which, the closer it is to 1:1, would favor the modulation of inflammatory responses associated with various diseases and their complications [30, 31].

Around 50% of respondents consume ready-to-eat adult S. purpurascens 1–2 times per week (Table 4); however, there is no significant relationship between the frequency of consumption and the amount of S. purpurascens ingested on each day of consumption.

According to the average ω-3 content of S. purpurascens (Table 2), the median daily consumption of all groups (Table 4) would provide 12.4% of the average daily ω-3 requirement for adults according to references [27] and between 7.3% and 23.2% if the interquartile range is considered. Likewise, with the fiber contribution from alfalfa-fed S. purpurascens, the median consumption of all groups surveyed (Table 4) would cover 39.7% of the daily fiber requirement for adults according to references [28] and between 23.1% and 73.6% if the interquartile range is considered.

Discussion

This exploratory study confirms a previous report in which alfalfa-fed S. purpurascens had a higher fiber content than corn-fed ones [6]. However, the fiber content identified here was, on average, 81.7% higher than that reported. This difference could be due to the fact that in the adult stage of the insect, the exoskeleton is larger than that of the nymphs [32] and therefore has a higher fiber content [33]; however, this must be verified with further studies that specify the stage of development of the samples analyzed, as this aspect is omitted in most previous studies.

The proportion of saturated fatty acids in the S. purpurascens samples analyzed here is just over double that previously reported [10, 12], implying a lower proportion of polyunsaturated fatty acids, which could be due to thermal degradation resulting from the temperatures [34] inherent in the cooking processes described here for S. purpurascens; but this finding should be treated with caution as the fatty acid profile was not performed in triplicate. It is evident that subsequent studies are required to substantiate or refute these proportions, while accounting for variables such as the insect’s developmental stage and the extent of its culinary processing.

This research provides preliminary guidance for establishing recommended amounts of regular consumption of S. purpurascens that may be useful for testing the effectiveness of its functional components. In this regard, it is imperative to acknowledge that overall diet composition constitutes a system, comprising a set of interdependent variables. Consequently, the functional effectiveness of a specific food can be augmented or neutralized, contingent on the quantity and quality of other foods regularly consumed.

However, among the main limitations of this study are its cross-sectional design (a single point in time, January 2019), its implementation in a single market, and the lack of replication in the fatty acid profile. Nevertheless, the evidence presented possesses heuristic value for future research on the effectiveness of the functional components of S. purpurascens.

Ultimately, the consumption of S. purpurascens harvested through sustainable extraction complements a production process in line with the 12th goal of the 2030 Agenda, which is to “Ensure sustainable consumption and production patterns” [35]. This is because it is a production-consumption system that involves avoiding the use of conventional chemical pesticides, which pose health risks, as well as obtaining nutrients—especially proteins—with a lower environmental impact compared to livestock farming [3].