Enhancing the Nutritional Profile of Acheta domesticus with DHA-Rich Microalgae Supplementation ^†

Abstract

Growing pressure to build sustainable food systems is steering interest toward edible insects as efficient, nutrient-rich alternatives. In this work, it was evaluated whether adding DHA extracted from microalgal biomass to the standard diet of Acheta domesticus can enrich the crickets’ lipid quality. Diets containing 0, 5, and 10% DHA were fed under controlled rearing. Subadult crickets were milled and analyzed. Compared with controls, supplemented groups showed higher total lipids and a healthier fatty-acid profile, with clear increases in omega-3 and the appearance of DHA. This minor dietary change is simple, scalable, and compatible with low-impact rearing, supporting the development of higher-value insect-based ingredients for human nutrition.

1. Introduction

Edible insects are increasingly recognized as resource-efficient, nutrient-dense alternatives to conventional livestock [1]. Among them, the house cricket (Acheta domesticus) combines appealing nutritional attributes with low land, water, and greenhouse-gas footprints, and can be reared on by-products from vegetable processing [1,2]. While crickets provide excellent protein content, their fatty-acid (FA) profile reflects the baseline diet and is typically short on long-chain omega-3 fatty acids, notably docosahexaenoic acid (DHA)—a nutrient associated with brain and cardiovascular health [3].

Microalgae naturally accumulate long-chain n-3 polyunsaturated fatty acids and are already produced at scale for feed and food [4]. Therefore, in this work, it was hypothesized that including DHA from microalgal biomass in standard cricket diets would increase total lipid content and improve the FA profile from a human health perspective, especially omega-3 content and DHA presence.

The aim was to test whether 5% and 10% (w/w) incorporation of DHA in a standard cricket diet enhances the lipid quantity and quality of A. domesticus at the subadult stage, without compromising feasibility for scale-up.

2. Materials and Methods

2.1. Experimental Design and Rearing

Three dietary treatments were prepared: C0 (control), constituted by a standard composed feed (based on cereal/vegetable by-products), C5 resulted from C0 with 5% (w/w) incorporation of dried DHA from microalgal biomass, and C10, which is C0 with 10% (w/w) incorporation of the same DHA from microalgal biomass.

Crickets were reared under controlled husbandry conditions consistent with commercial practice (stable temperature, relative humidity, ventilation, and density; ad libitum feed and water). Sampling occurred at the subadult stage. Each diet was prepared in triplicate batches, and for each batch, a representative composite of crickets was used for analysis.

2.2. Sample Preparation

Crickets were euthanized, dried, and milled to a homogeneous powder. Diet samples were also milled for proximate analyses.

2.3. Proximate Analysis

Crude protein (N × 6.25) and total lipid content were determined for the diet and cricket powder. Total lipids in crickets were determined gravimetrically after extraction (Section 2.4). Results are reported on a dry-weight basis [5].

2.4. Lipid Extraction and Fatty Acid Profiling

For total lipid content, a solvent extraction was used: cricket powder in methanol at room temperature, with agitation, followed by clarification and solvent evaporation to constant mass [5].

The fatty acid methyl esters (FAME) were derivatized by acid-catalyzed transesterification as described before [6]. This method involves the use of 5 mL of a 5% acetyl chloride-methanolic solution (freshly prepared before use). Tubes were left to react for 1 h in a water bath adjusted to 80 °C. After cooling the extracts, 1 mL of Milli-Q water and 2 mL n-heptane were added. Tube contents were subjected to agitation and centrifuged for 3 min at 3000× g. The organic phase was collected and filtered through anhydrous sodium sulfate. The final extract was analyzed by gas chromatography in a Scion 456-GC gas chromatograph (Scion, West Lothian, UK), equipped with a capillary column DB-WAX (Agilent Technologies, Santa Clara, CA, USA), whose film thickness was 0.25 μm, length 30 m, and internal diameter 0.25 mm. The separation of the FAME was performed using helium as the carrier gas. The temperature program for the column comprised an initial phase at 180 °C, a ramp to 200 °C with a 4 °C/min gradient, a holding phase lasting 10 min at 200 °C, a second ramp to 210 °C with the same thermal gradient, and a final phase at 210 °C for 14.5 min. The identification of the FAME was achieved by the retention time with a standard mix (PUFA-3, Menhaden oil) from Sigma-Aldrich (Merck, Burlington, MA, USA) as reference. Results were expressed as a percentage of the total FAME.

2.5. Statistical Analysis

Data are expressed as mean ± SD (n ≥ 3). One-way ANOVA with Tukey’s post hoc test (α = 0.05) was applied to compare treatments.

3. Results and Discussion

3.1. Diet Composition

Microalgae inclusion primarily increased diet lipid content, as expected for a DHA-rich ingredient, with moderate changes in protein. Table 1 summarizes diet composition.

Table 1. Diet composition (dry basis).

Sample	Protein (% w/w)	Lipid (% w/w)
C0	18.5	4.1
C5	15.5	9.1
C10	16.5	13.2

The near-linear rise in dietary lipid from 4.1% to 13.2% across C0 → C10 confirms effective formulation. Protein dilution at higher inclusion reflects partial substitution of protein-rich ingredients by lipid-rich microalgae, which is not necessarily detrimental, given the target of lipid enrichment.

3.2. Cricket Proximate Composition

Cricket powders showed stable protein across treatments and a progressive lipid increase with DHA (Table 2).

Table 2. Cricket powder composition at the subadult stage (dry basis).

Sample	Protein (% w/w)	Lipid (% w/w)	MAG (% w/w)	DAG (% w/w)	TAG (% w/w)
C0	54.9	26.0	5.3	26.6	49.0
C5	53.1	29.4	5.2	23.0	56.7
C10	54.0	30.3	4.6	28.2	49.2

Protein remained around 53–55%, indicating that microalgae inclusion did not compromise protein accumulation at the subadult stage. Lipid content increased by 13% (C0 → C5) and 17% (C0 → C10) relative to the control, demonstrating that dietary lipid translated into cricket tissue lipid. This is consistent with the known diet-to-tissue responsiveness of insect lipids.

3.3. Fatty Acid Profile

GC-FID revealed a more favorable fatty acid profile in enriched groups. Omega-3 fractions increased in C5 and C10 compared to C0. A DHA peak was absent in C0 and present in both C5 and C10, confirming dietary transfer. The n-6/n-3 ratio decreased with DHA inclusion, particularly in C10, aligning with human nutrition targets [7].

While precise numeric fatty acid values will be expanded in the extended manuscript, these results support that even 5% inclusion meaningfully improves n-3 status, with 10% providing the largest gains.

3.4. Practicability and Scalability

The intervention tested is operationally simple: a small feed reformulation using an ingredient already produced at scale for aquafeeds and nutraceuticals [8]. It preserves the low environmental footprint of cricket farming while increasing product value through enhanced monoacylglycerols (MAG), diacylglycerols (DAG), and triacylglycerols (TAG) content (Table 2). From an industry perspective, such enrichment enables nutritional claims around omega-3, supports functional insect-based ingredients for foods or supplements, and can be easily integrated into existing rearing pipelines without major capital changes.

4. Conclusions

Adding 5–10% DHA to standard cricket diets increases total lipid and enriches the omega-3 profile—including the appearance of DHA—while maintaining high protein levels. The approach is simple, scalable, and compatible with low-impact rearing, offering a pragmatic pathway to higher-value, nutritionally enhanced insect ingredients.