This article is part of
Wilderness Way
VOLUME 11, ISSUE 1.
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IMU:
Hawaiian Underground Oven
by Dino Labiste
Anyone who has
experienced a contemporary Hawaiian lu’au (feast) will find
kalua pig a main part of the menu. Traditionally, the pig
was cooked in an underground pit and served in plaited
baskets made of coconut fronds or on large banana leaves.
The shredded pork was just as tender and moist as pork
roasted in an electric or gas oven. The word kalua refers to
the process of cooking in an earth oven (ka, the; lua,
hole).
Throughout Polynesia, Melanesia, Micronesia, and even the
Americas, traditional underground ovens have been utilized
to cook and steam food. The Hawaiians used a pit oven,
called an imu, to steam whole pigs, breadfruit, bananas,
sweet potatoes, taro, chicken, and fish. The imu was
essentially an underground pressure cooker. Due to the
amount of time and labor to prepare the imu, most earth oven
cooking was done for group meals, festivities, or religious
ceremonies.
To build an imu, a lua, or round pit about 2 to 4 feet deep
with sloping sides is dug into the earth. The diameter and
depth of the lua will match the amount of food to be cooked.
The pit must be large enough to contain not only the food,
but also rocks and the vegetation. Keep the imu as compact
as possible. Place the excavated dirt next to the pit.
Later, it will be used to cover the imu.
Next, gather kindling material, like twigs, small branches,
and any other combustible tinder. Place the kindling
material in the bottom center of the pit. Larger wood
(preferably hardwood) is built around the kindling wood. Do
not use wood that will impart an unpleasant taste to the
food.
Stones, about the size of a closed fist, are then positioned
on top of the larger wood. Vesicular basalt stones are ideal
for imu cooking. These porous rocks retain heat and are less
likely to break. Stones that contain moisture, which causes
the rock to explode when heated, should be avoided. The
kindling wood is lighted and the blazing fire heats the pit
and the stones. As the wood turns to charcoal, the imu
stones drop inward on the hot coals. Firing time varies from
1-1/2 to 3 hours until the stones are at their maximum heat.
The hot stones are then leveled out with a stick or wooden
tongs to an even floor on top of the coals.
Since
the cooking process requires steam and not dry heat, green
plant materials are needed to create the steam. The
Hawaiians utilized grass and leaves for their imu cooking.
Some of the traditional plants were banana stumps, ti
leaves, honohono grass, banana leaves, and coconut palm leaf
(see the section on “Modern Adaptations on Imu Cooking” for
plant substitutes). The common term used today to describe
the green vegetation material and its use is hali’i, which
means, “to spread like the mat covering the floor.”
While
the stones are being heated in the pit, gather and prepare
any plant material you will need. If you will be using
banana stumps, they will have to be cut into sections
smaller than the diameter of the pit. The sections are
sliced lengthwise, either in half or quartered, depending on
the size of the trunk. Then, the sliced stumps are pounded
with a rock to break up the fibers and to release the
moisture in the stumps. If a whole pig is going to be
cooked, the skin and the inside cavity area are rubbed with
a small amount of rock salt. When the stones are about
ready, place all your food and vegetation materials near the
pit. Also, lay your covering material next to the imu.
Traditionally, the covering material before the final dirt
cover was old lauhala mats or worn tapa cloth.
When
the heated stones are ready, it is time to layer the imu
with green vegetation, food, covering material, and dirt.
The first layer of hali’i is laid directly over the hot
rocks to prevent the food from being scorched and to create
steam for cooking. If you have access to a banana trunk, use
smashed banana stumps. Next, a second layer of hali’i is
placed over the first layer. In Old Hawai’i, the green
vegetation was ti leaves. This second layer is important in
that it touches the food and adds flavor to the cooking
meal. The food is placed on top of the ti leaves. If you are
cooking a whole pig, a few hot stones are also placed inside
the body cavity to insure the pig is well cooked. A third
layer of hali’i covers the food. The old way used ti leaves
with young, whole banana leaves on top. The covering
material is then laid over the imu. The covering material
must extend beyond the diameter of the pit’s opening. This
will keep any dirt from falling into the imu when the food
is unearthed. The final layer is loose dirt, which is
shoveled over the entire covering material to prevent any
steam from escaping.
Estimating
the time it takes to cook the food depends on the heat of
the imu, the thickness of the hali’i, the kind of food, and
the mass of the food. A large whole pig, in a good hot imu,
may take from 4 to 6 hours of steaming time. When the
cooking is done, brush away any loose dirt from the edges of
the covering material. Remove the dirt from the lauhala mats
or tapa cloth. Carefully lift off the covering material and
avoid getting any dirt into the imu. Uncover the layers of
hali’i, and serve up your delicious meal.
