Physicochemical Characteristics, Microbial Quality and Sensory Acceptability of Cricket (Gryllus bimaculatus) Flour Preserved With Ginger, Garlic and Turmeric Extracts

Abstract

Insects are a vital and preferred food among many cultures scattered throughout the world, where they are consumed as a source of protein, fat, minerals, and vitamins. However, with majority of insects still collected from wild environments, their utilization is hampered by regional and seasonal availability, perishability, and high postharvest losses. Therefore, this study aimed to preserve the quality of crickets (Gryllus bimaculatus) commonly consumed in East Africa, using spice extracts and determine the physico chemical characteristics, microbial quality and sensory acceptability of cricket flour. Garlic cloves, ginger, and turmeric rhizomes (2.5 kg each) were acquired from a local food market in Northern Uganda (2.2581° N, 32.8874° E), packed in airtight bags, and transported to the Jomo Kenyatta University of Agriculture and Technology (JKUAT) food biochemistry laboratory in Kenya. Samples were carefully cleaned under tap water, and rinsed with distilled water, drained to eliminate excess water, grated and extracted using acetone, ethanol, methanol, and water (2 g in 30 ml). The solution was shaken for 1 hr and kept in the dark for 72 hrs. Standard techniques were used to determine phytochemical composition and antioxidant and antimicrobial activity. Based on the results, ginger and garlic, extracted with ethanol, was chosen for the treatment of blanched crickets and subsequent processing into flour. Blanched crickets were divided into 5 batches of 1000 g each; three batches were chosen randomly and mixed with extracts of ginger, garlic, or ginger+garlic at a ratio of 1:4 (v/w). The other two batches received 0.1% sodium benzoate (positive control) and distilled water (C) (negative control). Following a 30-minute soak in the appropriate solution; any excess was drained off prior to oven drying for two hours at 105 °C (until crisp dry). Samples were milled to flour and packed in packed in zip-top low-density polyethylene bags with a 10 µm thickness. The samples were kept on shelf at ambient conditions; room temperature (23±2 °C) and relative humidity (60±2 %) and subjected to physicochemical, microbiological, and sensory evaluation at days 0, 30, and 60 of storage to evaluate the changes in an interval on 1 month. Phytochemicals and antioxidant activity were determined using standard methods; the antimicrobial activity of extracts was investigated using the agar-well diffusion method against Staphylococcus aureus, Escherichia coli, and Candida albicans; representing the microrganisms that are of public health significance as they affect food quality and safety (cause food borne illness). The fatty acid composition was assayed using gas chromatography, while the sensory evaluation for color, aroma, texture/fineness, and overall acceptability was conducted using the hedonic test on a 5-point scale. Ginger extracts exhibited significantly higher total phenolic and flavonoid content in organic solvents compared to water extracts (p˂0.05). The highest total phenolic and flavonoid content was in ethanol and methanol extracts of local ginger; 1968.49 and 2172.65 mg GAE/100 g; 254.24 and 184.62 mg QE/100 g, respectively. Organic solvent extracts of turmeric exhibited significantly higher total phenolic and flavonoid content compared to aqueous extract; 1379.94, 515.60, 561.16, 307.45 mg /100g Gallic acid equivalence and 382.66, 411.88, 339.01, 158.11mg /100g quercetin equivalent in acetone, ethanol, methanol and water aqueous respectively (p˂0.05). Garlic extract followed the same trend as ginger and turmeric but with lower phenolic and flavonoid content.Vitamin C was significantly higher in aqueous compared to organic solvent extracts of ginger, garlic and turmeric (p˂0.05); This is of interest because vitamin C has antioxidant properties. Higher phenolic and flavonoids content in organic extracts resulted in a significantly higher free radical scavenging activity of the spice extracts. The strongest antioxidant activity was recorded in the turmeric-acetone extracts and in the acetone and ethanol extracts of the local ginger. Antimicrobial activity at 25 mg/ml varied significantly against the microorganisms, being highest on C. albicans and in the range of 18.00 to 30.67; 19.67 to 30.33; and 17.67 to 29.33 mm in ginger, garlic, and turmeric extracts, respectively. Raw garlic extracts exhibited higher antimicrobial activities against S. aureus, E. coli, and C. albicans. Activity of garlic ethanolic extracts compared favorably with raw extracts against the respective organisms (hybrid; 26.33, 24.33, 25.00; and local: 20.33, 20.33, 27.67 mm). Minimum inhibitory concentrations ranged from 2.5–10 mg/ml in garlic extracts. The major fatty acids in the cricket flour were linoleic, oleic, palmitic and stearic acid, respectively. During storage, slight increase in the proportion of palmitic acid and stearic acid and decrease in oleic and linoleic acid was recorded; changes in the proportions were more pronounced in the untreated samples.The acid value (AV), peroxide value (PV), and thiobarbituric acid reactive substances (TBARS) of flour all stayed within safe levels. Flour preserved with a ginger-garlic mixture showed minimal changes, compared favorably with sodium benzoate treatment. The pH, moisture content and total color change increased during storage but remained within acceptable limits. Fecal coliforms and Escherichia coli were not detected in any of the samples. On a five-point hedonic scale, (1. dislike extremely and 5. like extremely), color (3.84 to 2.55), aroma (3.59 to 2.40), texture (4.11 to 3.11) and overall acceptability (3.77 to 2.83) sensory scores were all significantly high on day 0 and low on day 60 of storage, respectively. According to the findings, ginger, garlic, and turmeric have strong antioxidant and antimicrobial activity, which makes them useful as natural antioxidants and antimicrobials. The study concluded that treating crickets with a combination of ginger and garlic minimizes lipid oxidation and that preserving crickets with ginger and garlic extracts produced flour that was safe, shelf-stable, and acceptable to consumers.