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The effect of freezing and freeze-drying on the physico-chemical changes in Northwest strawberriesRao, Akkinapally Venketeshwer 30 June 1966 (has links)
Preservation of food by freezing is a common method
of processing. Of relatively recent origin is the freeze-drying
method. This method has several advantages over
other methods of preservation, but is not free of problems,
one of which is the maintenance of appearance and
texture.
In the present study, the effects of freezing, thawing,
freeze-drying, and reconstitution on the physico-chemical
properties of Northwest variety strawberries
with particular reference to textural characteristics
were investigated. Very little prior work is reported
with regards to the effect of these factors on fruits.
Strawberries were frozen at two different rates of
freezing - slow frozen at 0°F and quick frozen in a
blast freezer at -20°F. Frozen berries were examined
by physical and chemical methods to evaluate the changes.
In a separate study, berries were thawed under standard
conditions of relative humidity and temperature and the drip collected for analysis. Thawed berries were examined
by both physical and chemical methods. To study the reconstitution
behaviour of the berries, they were freeze-dried
and reconstituted under standard conditions of berry
to water ratio, temperature of water and time of reconstitution.
Reconstituted berries and the remaining
solutions were then examined. Measurements of the texture,
color, total solids, alcohol insoluble solids, pectins,
cellulose, ash, and constituents of ash were made
on raw, frozen, thawed, and reconstituted berries. The
results indicated the following conclusions:
1. An increase in percent soluble solids, pH, and
titratable acids and a decrease in total solids and AIS
of the berries were observed upon freezing. Slow frozen
berries showed more pronounced effects. Smaller berries
were observed to change the least. No significant differences
were found in the other constituents.
2. Strawberries lose weight upon thawing depending
on the chemical composition of the berries. An inverse
relationship was observed between weight loss and total
solids, AIS, pectic substances, cellulose, ash and mineral
content of the berries. With gradual increase in the
weight loss upon thawing, there was a progressive softening
of the berries. A direct relationship was found between
weight loss and the amount of pectic substances,
sugars, titratable acids, ash, and minerals found in the drip. Slow freezing resulted in higher weight loss and
smaller berries lost the least.
3. A linear relationship exists between weight loss
of the berries upon thawing and the area of the drip.
This method offers a convenient and quick procedure for
evaluation of the quality of frozen strawberries, with the
added advantage of collecting the drip and storing it for
further analysis at a convenient time.
4. Ability to reconstitute was found to be related
to rate of freezing and size of berry. Quick freezing
and smaller berries gave the best results.
5. Direct relationship was found between the degree
of reconstitution and total solids, AIS, pectic substances,
cellulose, ash, and minerals. The amount of
pectic substances, sugar, titratable acids, ash, and minerals
leaching out of the berries into the reconstituting
solution were smaller and were independent of the degree
of reconstitution.
6. Individual berries showed a large variation in
their chemical constituents, which was responsible for
the differences in the thawing and reconstitution behavior
of Northwest strawberries. / Graduation date: 1967
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Freeze-drying of peasWosje, Duane Charles. January 1965 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 57-60.
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Mechanical compression of food products during freeze-drying through force produced by springs.Emami, Seid-Hossein January 1976 (has links)
Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Nutrition and Food Science. / Microfiche copy available in Archives and Science. / Bibliography: leaves 121-127. / M.S.
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Effects of rigor, salt, storage methods and time on the ultrastructure, chemical and organoleptic properties of beef /Kuo, James Chun-Chin January 1982 (has links)
No description available.
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Survival of freeze-dried probiotics in soy protein powderAubuchon, Emilie D. January 2006 (has links)
Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 21, 2007) Includes bibliographical references.
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Studies on the rehydration of irradiated freeze-dried beefNi, Yeng-Wei January 1969 (has links)
The total water uptake, rate of water uptake, extract release volume and maximum shear force were measured on a series of samples of irradiated freeze-dried beef. Forty seven pieces of round steak (2.5 cm x 2.5 cm x 10.4 cm or 1" x 1" x 4") were irradiated at one, three and five megarad. The control samples were not irradiated. Half of the samples were irradiated when fresh, and the other half were irradiated after freeze drying. This procedure has been defined as the "fresh-dry" irradiation sequence throughout the report. The samples were frozen in an air blast at two temperatures (-22.2°C and -56.1°C). Freeze-drying was carried out below 300 microns of Hg and a maximum shelf temperature of 15.6°C (60°F).
There appears to be three phases of water uptake:
1) A very rapid, almost instantaneous, absorption.
2) A more gradual uptake (called Part.1 in the report).
3) A relatively slow asymptotic approach to an equilibrium condition (Part 2). These two last phases are shown to be straight lines when the logarithm of the water uptake is plotted against the logarithm of the immersion time.
Irradiation level has no significant effect on the final water content or on the slow asymptotic absorption (Part 2) or the extract release volume, but has a significant effect on the gradual water uptake (Part 1) and on the shear press force. Fresh-dry irradiation sequence (and freezing rate) have a significant effect on the total water uptake and on the slow asymptotic water (Part 2) uptake, but not on the gradual water uptake (Part 1), or on the extract release volume or on the shear press forces.
Freezing rates have a significant effect on the total water uptake, but not on the slow asymptotic water uptake (Part 2), on the gradual water uptake (Part 1), on the extract release volume or on the shear press forces.
The highest total water uptake was found for the meat irradiated when fresh, and slow frozen at -2 2.2°C.
The mechanism of the gradual absorption appears to follow a phenomena of water flow, as evidenced by the straight line relationship found in the plots of logarithm water uptake versus logarithm immersion time. / Land and Food Systems, Faculty of / Graduate
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Collapse temperature of freeze-dried carbohydrate solutions : effects of composition and moisture content.Tsourouflis, Spyros Panayiotis Constantinos January 1975 (has links)
Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Nutrition and Food Science. / Bibliography: leaves 109-112. / M.S.
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Compression of foods during vacuum freeze dehydration.Emami, Seid-Hossein January 1979 (has links)
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nutrition and Food Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 153-157. / Ph.D.
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Storage stability of freeze dried raspberry and blackberry juicesPatton, Kathleen A. January 1986 (has links)
No description available.
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Storage stability of freeze dried raspberry and blackberry juicesPatton, Kathleen A. January 1986 (has links)
No description available.
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