- This thesis research is a series of five studies dealing
with various aspects of hazelnut quality:
1. Identification of kernel mold and its incidence among
2. Seasonal development and composition of kernels.
3. Hazelnut oil composition (fatty acids and
tocopherols) of seventeen varieties.
4. Hazelnut oil composition compared to 14 other nuts
5. Storage and roasting effects on lipid oxidation.
Barcelona, Daviana, and Ennis varieties of hazelnuts used
to study white mold showed that mold incidence was highest in
1986, and much less in 1987 and 1988. Ramularia spp was the
only fungus that was identified in all samples with kernel
mold and was usually found at high percentages. Temperatures
for drying, storage, and numbers of nuts per cluster had no
significant effect on percent mold.
The second part of this study measured fatty acid and
vitamin E concentrations during the growing season. Samples
were collected from seven varieties (Barcelona, Daviana,
Ennis, Tonda Romana, Tonda Gentile della Langhe, Tombul, and
Tombul Ghiaghli). Kernel oil and vitamin E (tocopherol)
concentrations increased with time, while moisture decreased.
Oleic acid was the major fatty acid (ca.75%) found in
hazelnuts, followed by linoleic(ca.20%). Linolenic was high
at the beginning of the season but then decreased to about 1%
at harvest. Alpha-tocopherol was the major form of vitamin E
found, composing almost 95% of total tocopherols. Hazelnuts
are a rich source of vitamin E, with about 350 μg/g oil.
Fourteen types of nuts, oil seeds, and seventeen
varieties of hazelnuts were compared for oil content, fatty
acid, and tocopherol composition. Macadamia nuts were the
highest in oil content (77%) and chestnuts were the lowest
(3%). Oil concentrations in oil seeds ranged from 5% in corn
to 50% in sesame seeds. Oil concentration also varied among
hazelnut cultivars. Hall's Giant had low concentrations (58%)
of oil and Tombul had high concentrations (66%) of oil.
Gamma-tocopherol was the dominant form in pistachios, English
walnuts, black walnuts, pinenuts, and Brazil nuts. All four
tocopherols were found in oil seeds and tocotrienols were
found in some. Hazelnut varieties were stable during storage
for up to two years with only slight loss in vitamin E.