What changes need to be made to espresso machine so it can function properly in space? I recently read this article about an Astronatur taking a "specially adapted espresso machine" with her to the space station and using it there to drink coffee.

Now this makes me wonder, what changes were made to the coffee machine so that it produced excellent coffee even in zero gravity?

All the article says is:


  Cristoforetti will be able to get her morning caffeine fix after celebrated Italian coffee makers Lavazza teamed up with space food specialist engineering firm Argotec to create a special and lightweight machine.


Which doesn't really give much technical information about the change itself.
I was able to dig up this press release:
http://www.lavazza.com/en/.content/document/pdf/PR_Italian-espresso-in-orbit.pdf

The first capsule-based espresso system able to work in the extreme
conditions of space is here. It is called ISSpresso and is the
brainchild of two Italian companies — Argotec and Lavazza — in
collaboration with the Italian Space Agency
Turin, 13 June 2014 – “An espresso coffee is what I miss most aboard
the International Space Station.” We have repeatedly heard this
comment from the Italian astronauts who for 13 years have been at
times working in the International Space Station, and today their
espresso wish is about to become reality. In fact, Argotec and Lavazza
are working together with the Italian Space Agency (ISA) to actually
bring the authentic Italian espresso onto the International Space
Station. So in the Futura Mission — the second long-term mission of
the Italian Space Agency aboard the Space Station — another Italian
astronaut of the European Space Agency, Air Force Captain Samantha
Cristoforetti, could not only be the first Italian woman to go into
space, but also the first astronaut in history to drink an authentic
Italian espresso in orbit.
Its name is ISSpresso. It takes its name from the International Space
Station (ISS), where it is to be installed. It is the first
capsule-based espresso system able to work in the extreme conditions
of space, where the principles that regulate the fluid dynamics of
liquids and mixtures are very different from those typical on Earth.
ISSpresso is the product of a project run by Argotec, the Italian
engineering company specialised in the design of aerospace systems and
European leader in the preparation of healthy and nutritious foods for
in-space consumption, and Lavazza, the historic Italian coffee brand.
ISSpresso is a veritable technological and engineering jewel, able to
deliver a perfect espresso in weightless environment. This is why it
was selected by the Italian Space Agency to be used aboard the ISS, in
the framework of the Request for Expression of Interest that the
Agency keeps constantly open to public-private partnership projects
and activities to be carried out in the ISS.
“Italian coffee is a beverage without borders — comments Giuseppe Lavazza, Vice President
of Lavazza — and we have been thinking about taking the espresso into
space for some time. Indeed, as far back as ten years ago we launched
the espresso into orbit artistically with the photographs taken by
Thierry Le Gouès and our Mission to Espresso calendar, which at the
time may have looked like a work of science fiction but was actually
just a vision of the future. In fact, today we are in a position to
overcome the limits of weightlessness and enjoy a good espresso — the
indisputable symbol of made in Italy products — on board the
International Space Station. We are proud to have worked on this major
project with Argotec, through the Lavazza Innovation Center, our
division dedicated to research and product innovation: a scientific
and engineering challenge which we hope will improve the living and
nutrition quality of astronauts engaged on long missions.”
“Our aerospace engineers — stated David Avino, Managing Director of Argotec
— have designed a new-concept coffeemaker, which is safe for the
astronauts and able to function in microgravity conditions, also
thanks to Lavazza’s experience as a leader in capsule extraction 2
systems. The functional project was already completed in June 2013:
Argotec had been working on it for about one year. This is an ultra
high-tech project which has led to innovative solutions, applicable
with immediate returns on Earth as well. ISSpresso is a technological
challenge that meets very stringent requirements, imposed by the
Italian Space Agency, in terms of technical functionality and safety.
In addition to the engineering aspect, Argotec is also taking care of
the European astronauts’ training and nutrition. Food provides an
important psychological support and being able to enjoy a good Italian
espresso may be just the right way to finish off the menu designed
especially for each astronaut, helping him or her to feel closer to
home.”
Roberto Battiston, President of the Italian Space Agency added:
“ISSpresso is a perfect example of the way ISA's decision to make ISS
national usage rights available to public-private partnership
initiatives can result in a valorisation of public resources for
technological, economic, and social objectives. The ISA will bring
ISSpresso aboard the ISS, thanks to bilateral cooperation agreements
with the NASA, as it shares with the project partners the objective of
improving the quality of life of ISS astronauts, as well as the
astronauts who will take part in future long interplanetary
exploration missions. At the same time, we are also proud to
contribute to the promotion of the image and spreading of the
Made-in-Italy brand at international or better “space”, level.”
A coffee break in space. A prototype of the space coffee machine is
currently being tested at Argotec’s laboratories and all the necessary
functional and safety checks. In a subsequent phase, Finmeccanica –
Selex ES will participate in the assessment activities aimed at
launching ISSpresso into orbit with the Futura Mission crew, one of
whom is the Italian astronaut Samantha Cristoforetti. The ‘corner
café’ on the ISS will be the hub for socialising on board the Station,
a sort of social network in space, a venue for getting together,
chatting and relaxing: an aspect that should not be ignored in
missions that keep the astronauts away from home for many months in a
very challenging environment. The innovative capsule system will also
be able to prepare not only a regular espresso, but also a caffè lungo
or hot beverages, such as tea, infusions and broth, so that food can
also be rehydrated.
Extra-terrestrial technology. Every tiniest detail
of ISSpresso is designed to respond to a scientific and engineering
challenge: in fact, the machine studies have enabled principles of
physics and fluid dynamics to be tackled, such as the difficulty of
handling liquids at high pressure and high temperature in a space
environment. Just think that the plastic tube carrying the water
inside a normal espresso machine has been replaced with a special
steel tube designed to withstand pressure of more than 400 bar. The
machine is so complex that it weighs about 20 kilograms since there
are back-ups of all the critical components for safety reasons in
accordance with the specifications agreed upon with the Italian Space
Agency. ISSpresso represents a technologically high-value project
which, besides increasing the variety of flavour in the astronauts’
menu, will help improve our understanding of the principles of fluid
dynamics and conditions in microgravity. Some of the solutions adopted
have led to international patents, which will be useful both for
future space missions and immediate terrestrial use...

tl;dr
It looks like its a heavy duty capsule system designed to withstand high pressure that not only makes coffee, but makes tea, broth, infusions and re-hydrates food.

Just found images on The Guardian:

And on http://walyou.com/lavazza-argotec-isspresso/