Bewertung des Einflusses verschiedener Garverfahren auf die sensorische und ernährungsphysiologische Qualität von frischen und TK Gemüsen anhand ausgewählter Parameter (English shop)

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The influence of different cooking methods on the retention of ascorbic acid,
D-tocopherol, E-carotene (all-trans and cis-isomers) and minerals in fresh and
frozen vegetables is examined.
In addition the percental relation between the cis- and all trans- isomers of
E-carotene is expressed as cis-/all-trans ratio.
Fresh Broccoli, red pepper, carrots and potatoes are boiled and stewed in a
pot and prepared in a steam oven, a pressure steam oven and in the
microwave. Fresh red pepper and carrots are boiled and prepared in a
combi-steamer with 100 and 60 % humidity. Further frozen broccoli and
frozen peppers are boiled, prepared in a steam oven and in the microwave.
The sensory quality of the cooking methods is examined by evaluation test
with scale [DIN 10 952].
Ascorbic acid, D-tocopherol and E-carotene are detected by HPLC [VDLUFA
1993; IZ-LUFA-ITL 1999; DIN EN 12823-2 2000]. The determination of the
minerals is made by the ash content [VDLUFA 1976 ].
Sensory evaluation shows that most of the evaluations lie in the range of high
quality and some in middle quality range.
Generally the hydrophilic substances (ascorbic acid and minerals) suffer the
highest losses by boiling while the other cooking methods with less water
show small to no losses.
Cooking of fresh broccoli generally leads to a release of the lipophilic
compounds (D-tocopherol and all-trans-E-carotene) while in the frozen
broccoli no change or a decrement occurs.
In the fresh and frozen peppers no change or a loss of D-tocopherol and
all-trans-E-carotene occurs whereby the cis-/all-trans ratio of the E-carotene
increases.
For better comparison between fresh and frozen vegetables in future
investigations both should originate from the same crop. Further the
preparation of frozen vegetables with methods of canteen kitchens is an
interesting point of investigation.