What Every Chef Should Have on Their Phone

Nobody reaches for their phone in the middle of service. That's not when the questions come.

They come at four in the afternoon, when you're setting up and you need to know whether agar disperses at 85 degrees before you commit six litres of stock to it. They come when the recipe is in cups and your scale only speaks grams. They come when a colleague asks for your gel recipe and you're about to photograph a page of your notebook again.

Prep is when you have a free hand and a question. Here's what's worth having ready.

Hydrocolloid ratios you can trust

This is the one that costs money when you get it wrong. Agar disperses hot, at 85°C — cooler than that and it never properly hydrates. Once set it holds up to around 85°C on a warm plate, which is what makes it useful for hot gels. Its working range is 0.5 to 2.0%, and where you sit in that range depends on what you want: nearer the bottom for something that still moves, nearer the top for a gel you can cut.

Xanthan runs 0.1 to 0.5% depending on how much body you're after, and it's one of the few that disperses cold as well as hot. Gellan sits between 0.1 and 0.8%, with high-acyl giving you soft and elastic and low-acyl giving you firm and brittle.

You either know these cold or you look them up, and the looking-up is the problem — most of what's online is either a food science paper or a blog post written by someone who has never worked a service. What you want is the working number: percentage, dispersion temperature, pH range.

Keep a reference you actually trust, because the alternative is dumping a batch.

Conversion, without doing it in your head

Every kitchen has recipes from somewhere else. American cookbooks in cups, an old chef's notebook in ounces, a supplier spec in kilos, a scale in grams.

Converting two thirds of a cup of cream to millilitres while you're already behind is a small, stupid tax you pay several times a week. It's also where mistakes creep in — not because the maths is hard, but because you're doing it distracted.

Yield, before you order

You need eight kilos of trimmed salmon fillet for Saturday. How much whole fish do you order?

Skinless salmon yields about 50%. Skin on, closer to 62%. Get that wrong and you either run out mid-service or you've bought four kilos you didn't need. Multiply that across every protein and every vegetable and it's where a lot of kitchens quietly lose money.

Yield percentages vary by supplier, season and how you butcher. But having a baseline beats guessing, and knowing that a baseline exists beats assuming you use everything you buy.

Sharing a recipe properly

A chef asks for your brioche. You photograph your notebook. They squint at your handwriting, scale it wrong, and it doesn't work.

A recipe that transfers properly carries the quantities, the yield, and ideally the cost. Scaled to what they need, not to what you make. This is more useful than it sounds — most recipe sharing between chefs is still photographs of paper, and most of it loses something in transit.

Sous vide, set before prep starts

Water baths take time to come up. That means you set the temperature at the start of prep, which means you need the number before you start — not halfway through.

Duck breast, pork belly, short rib, egg: all different, all somewhere in a range rather than at a single point, and the range depends on whether you're after texture or pasteurisation. Worth having in front of you rather than in your memory.

Allergens, when you write the menu

Not when the table asks — by then it's too late to change anything. The useful moment is when you're building the dish.

Fourteen allergens in the EU, and the ones that catch people out are never the obvious ones. It's the mustard in the vinaigrette, the celery in the stock, the sulphites in the dried apricots. Checking at the writing stage means you're not improvising an answer during service.

What I use

I built DigitalKnife because I kept having these problems and kept solving them badly — a notebook, a spreadsheet, three browser tabs and a calculator.

The free tools cover most of the above: temperature reference, weight and volume conversion, the seasonal calendar, allergens, yield percentages for 245 ingredients, sous vide times, and seven cards of the Molecular Lab. No account needed for those.

But the point of this post isn't the app. It's that these are the questions that actually come up during prep, and having them somewhere reliable — any reliable somewhere — is worth more than the tool you use to get there.