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Trying to plan the yield of a cricket farm, based on public available data.
One bit that I would really appreciate help with is how much powder does 1kg of dead wet crickets produce, assuming they are dehydrated and milled?
Hi piede828, - I refer you to Collavo, Glew, Huang, et al. "House Cricket Small Scale Farming", available as free pdf on-line. It is hosted by Researchgate & if you can not find it let me know.
Authors note in Table 27.7 different water % in crickets. Their own had 72.3% water & the team of Nakagaki with DeFoliart tested crickets having 74.2% water. The difference is due to the author's testing their crickets at age 45 days & the other team culling test samples at age 21 days. One earlier team reported their crickets having 68.4% water.
The referred to report has some interesting insights you may find useful determining at what age you harvest crickets for powdering. The issue of chitin is addressed with the observation that by harvesting before last molt you will encounter minimal chitin. Author's suggest "... best time ... for consumption ... about week 4 ... 5." ((" ... standpoint weight ... optimum ... between week 8 ... 9."))
I think we can assume consuming chitin is of marginal benefit unless chitin-ase enzyme activity exists. When you read a bug has "x" amount of protein bear in mind some is tied to chitin & not necessarily biologically available (part of processing chitin to chito-san involves stripping the protein off with alkali chemistry, which is not environment of a gut pH.)
Let's consider the assumption that harvesting crickets at maximum weight when reach a certain advanced age is logically the best. Authors have several data points that, to me, indicate this needs more specific calculating.
Before any misunderstanding the authors have data for 4 different diets. What we are now getting into is their conclusion of best diet of those 4, namely what their charts call "HRD" (or human refuse diet of our kind of scraps, namely left overs & peels from vegetables/fruits, rice/pasta, bread, cheese skins, yolks, pork/beef). So from now on I am only highlighting their references to crickets reared on that stuff.
These "HRD" fed crickets top weight was reached after 8 - 9 weeks. However only 47.5% actually lived that long.
Fig. 27.2 shows how many of 250 crickets in an original population is still alive every week. It reveals that after 4 weeks there are still 200 alive; whereas less than 125 were alive by 9th week.
Fig. 27.1 charts their average weight & my eyeball reading of the graph puts the 4 week weight average as 1.75 grams, while when let mature average weight was 4.25 grams.
Fig. 27.3 starts to generate a potential cost effectiveness insight. Basically as the population starts to fall ( see day 38 ) the individuals start to also gain weight by consuming more food.
An interesting way point may be when from day 45 to day 52 the population seems to hold steady (dropping again notably by day 59) & during those same days the individuals pick up weight by consuming more. What stands out to me is the data points for day 52; being that the population decline stabilized yet from day 45 their weight jump more closely matches their increased intake than later on (i.e; after 59th day in comparison to data for 66th day).
When look at Fig. 27.3 for the author's suggested week 4-5 age crickets ideal for consuming minimal chitin content we see data points for 31st & 38th day old crickets. From day 31 to day 38 their weight gain is not dramatic (right side of graph shows minimal intake change in grams consumed) & the population does not seem to show a lot of mortality.
Table 27.11 reveals that the food conversion "ECI" (efficiency conversion index) at 59th day on their diet was better (65 +/-1.73) than either at days 38, 45 (less conversion than others), 52 or 66 age (unfortunately has not earlier age "ECI") . If want to compare author's suggested 4-5 week palatability suggestion to what those crickets are getting for an "ECI" we would have to use 38th day's 63 +/- 6.11 "ECI"; which is almost as good as what the crickets show for 66th day "ECI" .
You can find their respective weights on the specific scraps" diet since 10th day in this chart. There may be a trade off worth calculating to see if feeding a diminishing population reaches a point that is not really cost efficient. As discussed with approximate ratios elsewhere in Forum, the "dressed" cricket carcass once take away the wings & legs is less than their fresh weight.
Granola bar with cricket flour was researched by Colombian student team Dayana Andrea Blanco Miranda & Daniel Felipe Giraldo Carrillo at the LaSalle Univ. Engineering Dpt. program for Food Tech. See (2016) free full on-line text in Spanish (I have not looked for English version) "Dessarollo de una barra tipo granola a base de harina de grillo Acheta domestics como principal fuente proteica."
For orientation I will skip to page 32 & point out the cricket flour (Table 6 reports composition as 67.1 protein + 5.9 % total carbohydrates, being mostly in exo-skeleton/chitin + 4% moisture) used was purchased from Thailand. Authors calculated that a product having 25% cricket flour, itself 76.8% protein, along with an amount of granola totaling itself 13.5% protein (Table 5 shows ingredients used & their respective ratios that create different % protein; in order of listing the ingredients are puffed rice, oatmeal, peanut, brazil nut & coconut ... Table 7 details the moisture content of these different granola ingredients) all blended with invert sugar syrup ("jarabe invertida"; syrup elaboration detailed in section 4.2.4 middle of page 34, Table 11 shows it to be 4.7pH & 85 Brix) & blended together comprising a 23 gram fabricated bar would contain 3.5 grams of protein.
Table 4 on has 12 different formatted ratios' tests ("ensayo"). Section 4.2.5 describes making ("elaboration") the different formulated bars; namely 1st weigh mix, blend well & then add invert sugar syrup, spread evenly on wax paper, let cool at room temperature & then cut (322 g ingredients gives 14 bars of 23 gram each).
Tables 9 & 10 (pgs. 43 & 44) give 12 different bar formulas' mg/gram amount ("cantidad") of the different essential amino acids (left hand list). Table 12 (pg.45) gives 12 different bar formulas moisture content ("% humedad"), % protein & % total carbohydrates. Table 16 (pg.49) shows that, depending on whether looking for a different variable the formula has to be different; basically that in terms of crumbling consistency for holding together as a bar ("fracturabilidad") the cricket flour can not be too large a percentage.
Pg. 62 gives the characteristics of the bar finally decided on after variable characteristic & taste testing + desirable amino acid profile. Table 26 breaks down the winning formula's components in the following order: moisture = 4.2 g/100g, protein = 36.42 g/100g., fat = 14.53 g/100g., ash = 1.81 g/100g., fiber = 6.25 g/100g, carbohydrates = 36.79 g/100g. & total calories= 423.61 kiloCal/100gram of sweetened cricket meal granola bar. This formula is given on pg.64 as being 50% granola, 25.1% cricket flour with 24.9% inverted sugar syrup.
Note: not edited for errors or auto-correct mistakes.
piede828, - So if you are using 45 day old crickets (72.3% water) & create a commercial grade cricket flour (4% water Thailand product) figure a reduction of 68.3% in weight making cricket "flour" from fresh original fresh weight of crickets. Thus I estimate you would be getting 31.7 grams cricket flour for every 100 grams freshly collected 45 day old crickets not subjected to water stress (too dry food or too hot conditions or parasite load).
Again piede828, - Rony Perez Paredes & Royer Rose's Sanchez in their thesis "Elaboracion y caracterizacion de harinas para consumo humano a partir de Acheta domesticus y Periplanetas americanas" available on-line as free full pdf in Spanish has other data points for residual moisture in cricket "flour". It is higher (5.63%) than commercial Thailand product (4%) reported above.
Diagram 2.7 (pg.27 of original text - not pdf page number) shows their tactic is selecting adult crickets ("grillos"), freezing them for 1 hour, drying them at 80 Celsius for 1 hour, grinding the frozen carcases (they used a hand mortar & pestle), then further drying at 110 Celsius for 2 hours & finally further grinding them into finer size; there are subsequently photographs of these operations.
On pg.39 (text not pdf) a picture showing the simple lab equipment used to calculate the protein content of 0.25 grams ("Kjeldahl" method; used Kjeldahl apparatus are sold on eBay). Beginning pg.70 (of text) Annex B describes their Kjeldahl methodology of sample processing.
Fat calculation used 2 grams extracted by hexane (solvent) via a recirculating solvent extractor "Soxhlet" apparatus set-up (shown pg.43 of text). Begining on pg. 74 (text) is the description of Soxhlet methodology of sample processing. Fig. B-5 is the actual piece of lab glassware that is the soxhlet extractor (sold used on eBay, requires a compatible sized boiling flask below & condenser above for cooling water tube in w/warm water tube out).
After determining ash ("ceniza", picture pg 43 of text) by baking 3 grams for 4 hours at high temperature (650 Celsius) they reverse calculated the carbohydrate content by reducing a crude weighed cricket "flower" amount by the previously determined % of protein, fat & ash - with the matter of moisture content still needing factoring in.
Table 9 (pg.53 of text) states their laboratory ("lab") reared crickets processed as described resulted in a cricket "flour" containing 5.63% moisture content ("humedad").
Table 10 data for their "lab" reared cricket flour was 60.66 g. protein/100grams + 31.21 g fat/100 grams + 4.37 g carbohydrates/100 grams + 3.76 g ash ("cenizas")/100 grams containing 541.01 KiloCalories/100 grams.