Our lab students produced ice cream for the second time this year.

It was absolutely delicious — and most impressively, using a hand-cranked ice cream maker, they achieved an overrun of 28.8%. A great result!

Next time, we’re aiming to break the 30% mark!

This year, our third-year students spent three months crafting Calpis, a sugared sour milk beverage, from scratch.

A delicate flavor, a full sweetness, and a perfectly balanced dilution ratio.

They did a wonderful job.

M17 medium is a widely used culture medium for lactic streptococci. When it was first reported by Terzaghi & Sandine (1975), one of the reference media used for comparison was T5 medium (Thomas et al., 1974). T5 medium contains phosphate salts and shows buffering capacity equivalent to that of M17 medium, making it an excellent choice for lactic streptococci that produce large amounts of lactic acid. However, T5 medium was found to form a precipitate, and the authors concluded that the clear M17 medium was superior. Fifty years later, M17 medium has become the standard.

When I read the description that T5 medium produces a precipitate, I thought, “Hmm, is that so?”—and decided to prepare it myself. The resulting medium was perfectly clear, with no precipitate whatsoever. Then it clicked: perhaps they had used tap water rather than distilled water. I have heard that tap water in many countries outside Japan is hard water, which contains high concentrations of dissolved minerals. Phosphate ions tend to form precipitates with calcium ions, yet the composition of T5 medium includes no calcium —leading me to hypothesize that the water itself was hard.

So I prepared T5 medium using Contrex (total hardness: 1,468 mg/L; Ca: 468 mg/L; Mg: 74.5 mg/L), a mineral water well known for being extremely hard. And the result?

The medium became turbid with a white precipitate.

From this, I concluded that T5 medium prepared with distilled water is clear and practical. It remains possible that the phytone and yeast extract used in T5 medium available at the time contained higher levels of minerals than today’s highly purified reagents—meaning that even when distilled water was used back then, the medium may still have precipitated. In other words, the absence of precipitation I observed may simply reflect the improved purity of modern laboratory reagents.

In any case, the key takeaway is this: when prepared under modern laboratory conditions with distilled water, T5 medium is clear.

While walking through the laboratory, I came across the universe beetles on a desiccator.

Yesterday, we held a welcome party for the new third-year undergraduate students (a cherry blossom viewing at Hirosaki Park). The cherry blossoms were in full bloom at just the right time.

In this same spirit, we were delighted to welcome two new members to our laboratory. We look forward to working together over the next two years.

We are grateful to the fourth-year undergraduate and graduate students who handled all the preparations.