I have watched bad boba cooking for over a decade. Hard cores, clumping, going stale within minutes, overcooking into mush — four problems, and eight out of ten shops hit at least one. Most owners blame their own technique: they switch cookware, watch tutorials, time everything, and still get the same result. Most of the time it is not you — it is the pearls you bought.

I entered the industry in 2009, from milk tea shop worker to supply-chain buyer. I have handled no fewer than eight hundred batches of pearls. This article covers both ends — selection and cooking — so you can judge whether the bag of pearls in your hand is up to standard.

Quick summary (TL;DR): ① Understand the product: tapioca pearls are cassava starch — the ingredient list must start with cassava starch; ② Process: modified-starch pearls are the stable commercial choice (20-30% pricier than raw-starch); ③ Four indicators: ingredient list first item, uniform particle size, dryness, and yield rate (2-2.5x; below 1.8 means poor value); ④ Cooking: boiling water drop-in, 1:8 water ratio minimum, 25 min boil for 8mm pearls, 20-30 min rest, ice-water shock; ⑤ Procurement: batch consistency beats everything — demand per-batch test reports.

What exactly are pearls?

The body of a pearl is cassava starch — starch extracted from cassava (also called yuca or manioc in the south). Add water and sugar, knead into a dough, roll into balls, dry — that is the raw pearl.

Why cassava starch specifically? Because of its high amylopectin content: after gelatinization it is elastic, translucent, and does not retrograde (turn hard) easily when cooled. Corn starch and potato starch can be used too, but the texture is far worse — corn starch pearls turn brittle, potato starch pearls turn sticky. Neither has cassava's signature "chewy with a slight bite".

But cassava starch itself varies in grade. Origin matters a lot — Thai and Vietnamese cassava starch, and the stuff from Guangxi and Hainan, have different amylose/amylopectin ratios, which changes the finished pearl's texture. This is not mysticism, it is raw-material character; experienced tasters can tell in one bite.

Three production processes — they decide how easy the pearls are to cook

Commercial pearls on the market fall into three types, with big price and quality gaps.

Raw-starch pearls: cassava starch formed directly. Cheapest, but least stable. Different batches of cassava starch gelatinize differently — this bag cooks right at 15 minutes, the next bag still has hard cores at 20. Most common in small-workshop products.

Modified-starch pearls: made with cross-linked or esterified modified cassava starch. Gelatinization is more stable after modification, batch consistency is good, they resist overcooking and storage, and the cooked pearls hold their chew longer. Reputable large factories basically all go this route; price is about 20-30% higher than raw-starch pearls.

Blended pearls: cassava starch + other starches + thickeners + emulsifiers. Read the ingredient list length — short is not necessarily bad, but an especially long one (seven or eight additives and up) usually means a "fake chewy" texture: a brittle snap rather than the natural bounce of starch.

How to tell them apart? Read the ingredient list. A list with just "cassava starch, white sugar, water" is basically raw-starch or lightly blended; a name like "acetylated distarch phosphate" means modified process; a long string of thickeners and emulsifiers means heavily blended.

Blended is not automatically bad — in commercial use, moderate modification and blending actually improves stability. But the mouthfeel of additive-stacked products versus real starch texture — regular customers can tell.

Four hard indicators when buying

First, the first item on the ingredient list must be cassava starch. If water or white sugar comes first, starch content is insufficient — the pearls either fail to hold shape or retrograde fast. Some low-price pearls cut cost by blending corn starch into cassava starch and label it "edible starch" — pass on those.

Second, particle size uniformity. Pour a handful onto a flat surface and eyeball whether sizes are consistent. If particle sizes vary widely, under the same cooking time the small ones turn to mush while the large ones still have hard cores. Reputable factories screen to very tight tolerances; no-name brands often skip screening entirely.

Third, dryness. Grab a handful and squeeze: properly dried pearls make a crisp clicking sound as they collide and feel hard. Damp, soft, compressible pearls mean poor drying or moisture damage in storage — cooking time becomes completely unpredictable.

Fourth, yield rate. Dry pearls absorb water; the normal yield is 2 to 2.5 times dry weight. One kilo of dry pearls should yield 2 to 2.5 kilos cooked. Some pearls yield under 1.8 — you are paying the same money for more water, and per-cup cost goes straight up.

You cannot know particle size and yield without testing. So when choosing a supplier, ask for samples and cook them with fixed parameters — the data will speak for itself.

Cooking parameters: this part is free

Even with the right pearls, wrong cooking ruins them. Here are the stable parameters I have used in my own shops for years.

Water ratio: at least 1 part pearls to 8 parts water; 10 is safer. Too little water means incomplete gelatinization and certain hard cores.

Drop-in timing: add pearls only when water is fully boiling, stirring as you go. Dropping into warm water is the single biggest cause of hard cores — no contest.

Boil time: depending on particle size, standard 8mm pearls boil hard for 25 minutes. Note: the boil must stay at a rolling boil for the whole time — a gentle simmer does not count.

Resting: turn off the heat, cover, and rest 20 to 30 minutes. Resting is as important as boiling — heat slowly penetrates to the core. Skip the rest and you get pearls that are mush outside and hard inside.

Ice-water shock: scoop out and quickly shock in ice water. The texture tightens immediately and chewiness jumps a level. Skip this step and pearls go soft and lifeless.

Storage: drain, toss with sugar or honey, hold in a warmer at 60°C, use within 4 hours. At room temperature they start hardening and retrograding after 2 hours. Do not be sentimental — throw out stale pearls; a customer biting a hard core is the real loss.

The per-cup math: commercial pearls run 6-9 yuan per 1kg bag; per cup uses 25-30g dry weight, so pearl cost is roughly 0.3-0.5 yuan. Such a cheap ingredient ruining a 15-yuan cup of milk tea is a bad trade by any math.

Commercial procurement: my rules

Pearls are the category where I changed suppliers most often, and only settled in recent years — pearls have special quirks.

Rule one: batch consistency beats everything. If jam is a bit more sour this batch and sweeter next, customers barely notice. If pearls need 20 minutes this batch and 30 the next, your staff is stuck on the spot. So I only work with suppliers who guarantee batch stability — modified process, automated production line, and full inspection before shipment; all three are non-negotiable.

Rule two boils down to one sentence: every batch comes with a test report. Microbiology, moisture, sulfur dioxide residue — the report travels with the batch. Pearls are eaten directly, and cooking takes only ten-something minutes; if the raw material is bad, there is no recovery. A supplier once quoted 20% lower; I asked for test reports; a week later they sent a scan with obvious Photoshop marks. Blocked immediately.

Rule three: trial new products in small batches first. A supplier claims their "long-lasting pearls hold 8 hours" — cook a batch yourself and taste at hour six. Believe about 30% of the marketing page; let your tongue and timer decide the rest.

Common traps

Believing influencer tutorials wholesale. The viral "boil 10 minutes, rest 10 minutes" is for small quick-cook pearls. Apply it to standard 8mm commercial pearls and hard cores are guaranteed. Start from the manufacturer's reference parameters on the package, then fine-tune.

Cooking too much at once. Prepping extra for the lunch rush is understandable, but pearls are at their best within 2 hours of cooking. Better to cook in two batches than one day's worth in a single pot.

Soaking in syrup instead of tossing with sugar. Peals scooped into syrup keep soaking, and the syrup temperature slowly "stews" them soft. The right way: drain, then toss with granulated sugar or honey so each pearl gets a thin coating.

Freezing cooked pearls. Freezing then thawing destroys the starch structure with ice crystals — thawed pearls turn grainy and hard. Cooked pearls are made-to-order; there is no second path.

Buying no-name brands to save money. Pearl is the category with the densest low-price traps. Anything 30% below market price means either adulterated starch or shrunken drying/screening processes. Every few yuan you save per kilo comes back as hard cores in your customers' cups, with interest.

Final words

This unremarkable little ingredient is the hidden gatekeeper of your repeat-purchase rate. Customers may not say exactly what is off with a so-so tea base, but one hard core and they know instantly.

Three sentences for buying: cassava starch first on the ingredient list, batch consistency above all, test reports as a one-vote veto. Four things for cooking: drop into boiling water, boil long enough, rest it through, shock in ice water.

The rest — trust your tongue.

FAQ

Q1: Why do my pearls always have hard cores? — Usually the pearls, not your technique. Check the ingredient list (cassava starch first?), the process (modified is more stable), and your cooking: always drop into fully boiling water, keep a rolling boil, rest 20-30 minutes, and shock in ice water.

Q2: How do I tell raw-starch, modified and blended pearls apart? — Read the ingredient list: three simple items = raw or lightly blended; "acetylated distarch phosphate"-type names = modified process; a long list of thickeners/emulsifiers = heavily blended.

Q3: What is the yield rate and why does it matter? — Cooked yield should be 2-2.5x dry weight. Below 1.8 means you are buying more water; per-cup cost climbs for the same quality.

Q4: Can I freeze cooked pearls to store them? — No. Freezing and thawing destroys the starch structure; thawed pearls turn grainy and hard. Cooked pearls should be made fresh — toss with sugar, hold at 60°C, use within 4 hours.