R3. Commercial phase-change (eutectic) cold-storage products as a substitute for the NH4Cl goop

Date of survey: 2026-08-30. All prices are listing prices seen on that date at the URL given. Where a page blocked automated access, or showed no price, the entry says so. Nothing below is a guess dressed up as an observation.

Context: Tech Ingredients video 2 (2026-08-29, https://www.youtube.com/watch?v=IGlZ61oCcEY) fills PET sports-drink bottles with a 705 g water / 295 g NH4Cl eutectic (29.5 wt% NH4Cl, claimed melting point -15.4 C), plus 4 g bentonite, 20-25 g chopped carbon fibre and 12 g xanthan. The point of the goop is to be a rechargeable cold battery inside the freezer so the fan (video 1) has somewhere to dump heat other than the stored food. This document asks: what can you buy instead, what does it cost per kJ of latent heat, and what happens if it leaks onto food.

Two numbers to keep in mind while reading.

• Ice: 334 kJ/kg at 0 C. Every "gel pack" that is water plus a gelling agent has exactly this behaviour. The video measured it: gel pack and plain water plateaued at 0 C together.
• Cooling 10 kg of stock from 60 C to 3 C removes about 10 kg x 4.18 kJ/kg.K x 57 K = 2,400 kJ. So 20 kg of a 300 kJ/kg PCM (6,000 kJ) buys roughly 25 kg of hot liquid per full recharge, before counting the compressor's own contribution (about 45 W net in the video's household freezer, more in a commercial box).

Recharge rule that matters more than any brand: the freezer air has to sit several degrees below the PCM melting point for many hours to refreeze it. Arctic Ice says freeze Tundra (-15 C) at "below -5 F" (-20.5 C) for 24-36 h (https://arctic-ice.com/products/tundra-series). Frigolab says 6 C below the plate temperature for 24 h (https://www.frigolab.eu/gb/option-and-accessories/842-eutectic-plate-cold-gn-11-18c.html). A commercial reach-in that holds -18 to -23 C can recharge a -15 C PCM overnight. It cannot reliably recharge a -21 C PCM. That single fact rules out most of the "-21 C" pharma products for this job unless the freezer runs at -26 C or colder.

1. Consumer and outdoor cooler packs

Summary for section 1: only Arctic Ice Tundra and Engel 5 F are genuine -15 C eutectics in consumer packaging. Everything else is either water (0 C), a -2 C beverage pack, or a -7 C brine gel.

2. Industrial and pharma cold-chain PCMs, -10 to -25 C

What this table says for a commissary: the materials with the highest latent heat at -15 C (PLUSS HS15N 341, PureTemp -15 301, Rubitherm SP-17 300 kJ/kg) are all quote-only or sold by the gallon into your own containers. The only shelf-priced industrial format is the Sonoco/Fisher PureTemp brick, and at $0.21 per kJ it is five times the consumer-pack price.

3. Eutectic cold plates for vehicles and mobile freezers

These are welded steel or rotomoulded PE plates with internal refrigerant coils (vehicle type) or plain sealed plates (foodservice type), filled with a salt-water eutectic. Vehicle plates are recharged by the truck's own condensing unit, not by a freezer, and are sized by BTU holdover, not sold by the kilogram.

• Dole Refrigerating (Lewisburg TN): Cold-Cel holdover truck plates, Econo-Cel blower plates, plate freezers. "We don't have standard sizes", custom, contact for quote (https://www.doleref.com/eutectics). The CE catalogue PDF at doleref.com returned an HTML placeholder on 2026-08-30, so eutectic temperature options and BTU tables could not be read. No price.
• C Nelson Manufacturing (Oak Harbor OH): cold-plate carts and truck freezers with steel eutectic plates in three temperatures, -12 F (-24 C) novelties, 0 F (-18 C) ice cream, +26 F (-3 C) refrigeration; hold 8-10 h (https://cnelson.com/collections/refrigerated-eutectic-cold-plates). Web prices show $0.00, call 419-898-3305. Models VBD4SE (30 in) to VBD14SE (88 in).
• FIC S.p.A. (Italy): eutectic plates at -4, -11, -23, -26 and -33 C for last-mile transport (https://www.fic.com/en/tipologie-prodotto/eutectic-plates, via search snippet; the page returned 404 on direct fetch). Quote only.
• Frostcar (Turkey): models FP077 to FP177, no specs on page (https://www.frostcar.com/eutectic-plates/).
• Thermal Custom Packaging (TCP): -21 C hard-shell PCM, see section 2. Not vehicle plates.
• "Hercules" eutectic plates: no product page found before the search budget ran out. Unverified.
• Turnkey-parlor sites quote Chinese eutectic-plate ice cream truck bodies at about US$8,000-10,000 per set (https://turnkeyparlor.com/cold-plates-cool-packs-keep-ice-cream-cold/ and made-in-china listings).

Verdict: vehicle plates are the wrong tool. They are sized in tens of kg each, need a refrigerant connection to recharge, and are priced as capital equipment. Nothing here beats a stack of 5 lb consumer packs for a freezer-internal cold battery.

4. Foodservice eutectic plates, freezer cold accumulators, dry-ice alternatives

European foodservice catalogues sell GN-sized sealed PE plates with -21 C, -18 C, -12 C, -3 C, 0 C and +21 C fills. These are exactly the "buy" version of the video's bottles, but they are sold in Europe and shipping 5 kg plates across the Atlantic eats the price advantage.

• Frigolab (Italy): Eutectic plate COLD -18 C, GN 1/1 530 x 325 x 30 mm, 5.1 kg; GN 1/2 325 x 265 x 30 mm, 2.45 kg. EUR 89.00 ex VAT (EUR 108.58 inc), minimum 2 (https://www.frigolab.eu/gb/option-and-accessories/842-eutectic-plate-cold-gn-11-18c.html). Energy capacity not stated; at a typical 200-250 kJ/kg that is about 1,000-1,300 kJ per plate, EUR 0.07-0.09 per kJ before shipping.
• Kangabox UK: Premium cold plates in -12 C or -21 C, GN 1/4 GBP 37.40, GN 1/2 GBP 43.35, GN 1/1 GBP 65.45, Euronorm 60 x 40 GBP 79.00, all ex VAT (https://www.kangaboxuk.com/hot-and-cold-eutectic-plates-24-c.asp). Weights not listed.
• Reysan Atlantic UK: -21 C "saline" plate in HDPE, 48 x 28 cm, 4.5 kg, "latent heat 210 kcal" (879 kJ, so about 195 kJ/kg); -3 C version 4.1 kg, 230 kcal. Out of stock, "ask for price" (https://www.reysan.co.uk/cold-accumulator-eutectic-plate.aspx).
• Olivo (France): 13 plate models in rotomoulded PE, from 250 cc cartridges (0.3 kg) to GASTRO 1/1 (530 x 325 x 35 mm, 5.3 kg); seven fills at +21, 0, -3, -12, -17, -21, -26 C; "water, mineral salts, and refrigerants", non-toxic. No price (https://www.olivo-logistics.com/en/eutectic-plate/).
• Melform (Italy): 800 x 480 mm plates at +3 C, -21 C, and "extra frozen -21 C"; recyclable shell, "non-toxic internal liquid"; price shown as EUR 0.00, minimum 2 (https://www.melform.com/en/product%20category/foodservice-en/eutectic-plates/).
• Cold & Co (France): Rigid eutectic gel -20 C in HDPE with reinforced corners, "delivers cold between -30 C and -18 C", needs 48 h at -30 C or 24 h at -40 C to charge, sold in lots of 12, no price (https://www.coldandco.com/products/rigid-eutectic-gels-minus-20-degree/).
• Tempack (Spain): rigid frozen packs, phase change -21 C, HDPE over eutectic gel, no price (https://tempack.com/en/products/cold-packs/eutectic/eutectic-cold-pack-detail).
• Ice cream cold-plate dipping cabinets (C Nelson, Kelvinator, etc.): the plate is the cabinet's own eutectic and is not removable. KaTom's category page blocked automated access. Not relevant as a freezer insert.
• Dry-ice alternatives: every product above is marketed as one. The honest comparison is per kJ: dry ice gives about 571 kJ/kg of sublimation at -78.5 C and costs whatever your local supplier charges per delivery, but it is single-use and displaces oxygen in a walk-in. A -15 C eutectic pack is reusable thousands of times and its only running cost is the freezer's electricity to refreeze it.

5. Food-grade alternatives to NH4Cl for a home brew

Eutectic points below are the standard literature values. The latent heat figures for NaCl, NH4Cl and KCl are from the Zalba, Marin, Cabeza and Mehling 2003 review table (Applied Thermal Engineering 23, 251-283), quoted from memory and not re-fetched on 2026-08-30; corroboration from sources fetched today is noted per row. Salt prices are US retail listings seen 2026-08-30.

Note on the video's ratio. 295 g NH4Cl in 705 g water is 29.5 wt%, well above the 19.5 wt% eutectic. At 29.5 wt% the mixture is on the salt-rich side of the eutectic: NH4Cl solubility is 29.4 g/100 mL at 0 C (Wikipedia data above), so roughly 60 g of the 295 g will simply not dissolve at freezer temperatures and sits as solid salt doing nothing. The mixture still freezes at the eutectic temperature, which is why the video's plateau came out near -15 C, but a 19.5-20 wt% mix (about 200 g NH4Cl per 800 g water) gives the same plateau with a third less salt and more latent heat per kilogram. Worth checking against the video's claim that "the exact recipe is in the description" before copying it. The bentonite, carbon fibre and xanthan are sensible; xanthan is a food gum, bentonite is a wine fining agent, chopped carbon fibre is inert but not something you want in a sauce.

Corrosion warning for any home brew: Yilmaz 2010 found galvanised steel corroded at 4-5.7 g/m2.day in 21% NaCl and copper at 3.2-3.3 g/m2.day in dilute KCl, while stainless 304 and aluminium showed no mass loss in a month (aluminium did bubble). Keep the brine in PET or HDPE, never in a metal hotel pan, and keep it off the freezer's aluminium evaporator fins. The video's warning about steel wool is right.

Which to pick for a home brew:

• NaCl eutectic at 23.3 wt%: -21 C, 222 kJ/kg, $0.45 of salt per kg, and it is the only one of these you could spill on a brisket and shrug. The catch is the recharge rule: a freezer at -18 to -20 C will not refreeze it. Only do this if the freezer verifiably holds -25 C or colder.
• NH4Cl at 19.5-20 wt%: -15.4 C, about 289 kJ/kg, $2-4 of salt per kg. Recharges in any -18 C freezer. Food additive, but smells of ammonia and you would not want it on food. This is the video's choice and for a -18 C box it is the right one on physics.
• KCl at 19.5 wt%: -10.7 C, 253-283 kJ/kg, salt-substitute safe. Too warm to be a good sink for a freezer, fine for a refrigerator-side cold battery.

6. Ranking: top 3 buy-not-build for 20-40 kg at -15 to -21 C

Price per kJ uses observed listing price divided by (pack mass x latent heat). Where the latent heat of a consumer pack is not published, 301 J/g (PureTemp -15) is used and marked "assumed". For a -18 C commercial freezer the usable candidates are -15 C products; -21 C products are listed for completeness with the caveat that a -18 C box cannot recharge them.

Build option for comparison, same basis: NH4Cl at 19.5 wt% in free PET bottles, salt at $11-19/kg, about 289 kJ/kg, comes to $0.007-0.013 per kJ for the salt, or roughly $0.015-0.025 per kJ once you add carbon fibre, xanthan, bentonite and an hour of mixing per 10 bottles. That is 2-3x cheaper than Engel per kJ and 10x cheaper than the Fisher bricks. NaCl at 23.3 wt% is $0.002 per kJ but needs a -25 C freezer to recharge. The buy case rests on not wanting to handle 6-12 kg of ammonium chloride and 20-40 PET bottles in a food prep area, and on the packs being rigid, labelled and dishwasher safe. At $270-540 for 20-40 kg of Engel packs versus perhaps $100-150 of ingredients and an afternoon, buying is defensible; it is not the bargain the brands imply.

What could not be verified

• Latent heat of Engel 5 F, Arctic Ice Tundra, Cooler Shock, Polar Tech Ice Brix and all EU foodservice plates: none publish it. The 301 J/g assumption for the two -15 C consumer packs rests on Arctic Ice being PureTemp and Engel looking like the same OEM product.
• PureTemp sample store (store.puretemp.com) did not resolve, so the $12-24/lb figure is the FAQ statement, not a cart price.
• Rubitherm, PLUSS, Axiotherm, Climator, va-Q-tec, Cryopak, TCP, IPC, CCT, Pelican BioThermal, Dole, C Nelson, FIC, Olivo, Melform, Tempack, Cold & Co: quote only, no unit price observed.
• Zalba 2003 latent heats (NaCl 222, NH4Cl 289, KCl 283 kJ/kg) were not re-fetched; ScienceDirect and MDPI returned 403. The KCl figure is corroborated by a 2021 paper (253 measured, 284 literature) and the NaCl eutectic temperature by Yilmaz 2010.
• Home Depot, Lowe's, Walmart, eBay, REI, yeti.com, KaTom and engineeringtoolbox blocked automated fetches; prices from those retailers come from search snippets where cited and should be re-checked in a browser.
• "Hercules" eutectic plates: no product page found.
• Search budget for the session was exhausted at 200 queries; remaining lookups were direct fetches only.