15 research outputs found
Recommended from our members
The effect of freezing and freeze-drying on the physico-chemical changes in Northwest strawberries
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
Recommended from our members
Effect of processing and storage on the texture of canned berries
The texture of processed berry fruits changes both during processing
and subsequent storage. A study was made of these changes
in processed strawberries, raspberries, blackberries, and blue-
berries, spin-cooked and stored at 100°F. for 28 days in tin and
glass containers. Four samples, from each of the two replications of
the above, four berries,were analyzed immediately after processing
and after 3, 7, 14, and 28 days of storage at 100°F. Physical measurement
of texture was obtained by the use of Maryland Shear-press.
The work diagrams thus obtained were studied in detail. These samples,
after being subjected to the Shear-press, were analyzed for percent
A.I.S. and total pectin.
The results indicated the following:
1. There was no significant difference in the texture, percent A.I.S.
and total pectin, between berries processed and stored in tin and glass containers over a period of 28 days at 100°F,
2. Highest correlation was obtained between texture as measured by
partial work and total pectin in case of strawberries and blueberries
and between maximum force and percent A.I.S. in raspberries
and blackberries.
3. Maryland Shear-press gave characteristic work diagrams for
each of the four berries, which were consistent throughout.
4. A linear relationship was obtained between sample size and texture
as measured by the total work
Cytochrome P450 1A2 (CYP1A2) activity, mammographic density, and oxidative stress: a cross-sectional study
INTRODUCTION: Mammographically dense breast tissue is a strong predictor of breast cancer risk, and is influenced by both mitogens and mutagens. One enzyme that is able to affect both the mitogenic and mutagenic characteristics of estrogens is cytochrome P450 1A2 (CYP1A2), which is principally responsible for the metabolism of 17β-estradiol. METHODS: In a cross-sectional study of 146 premenopausal and 149 postmenopausal women, we examined the relationships between CYP1A2 activity, malondialdehyde (MDA) levels, and mammographic density. In vivo CYP1A2 activity was assessed by measuring caffeine metabolites in urine. Levels of serum and urinary MDA, and MDA–deoxyguanosine adducts in DNA were measured. Mammograms were digitized and measured using a computer-assisted method. RESULTS: CYP1A2 activity in postmenopausal women, but not in premenopausal women, was positively associated with mammographic density, suggesting that increased CYP1A2 activity after the menopause is a risk factor for breast cancer. In premenopausal women, but not in postmenopausal women, CYP1A2 activity was positively associated with serum and urinary MDA levels; there was also some evidence that CYP1A2 activity was more positively associated with percentage breast density when MDA levels were high, and more negatively associated with percentage breast density when MDA levels were low. CONCLUSION: These findings provide further evidence that variation in the activity level of enzymes involved in estrogen metabolism is related to levels of mammographic density and potentially to breast cancer risk
Phytochemicals - A Global Perspective of Their Role in Nutrition and Health
Phytochemicals are biologically active compounds present in plants used for food and medicine. A great deal of interest has been generated recently in the isolation, characterization and biological activity of these phytochemicals. This book is in response to the need for more current and global scope of phytochemicals. It contains chapters written by internationally recognized authors. The topics covered in the book range from their occurrence, chemical and physical characteristics, analytical procedures, biological activity, safety and industrial applications. The book has been planned to meet the needs of the researchers, health professionals, government regulatory agencies and industries. This book will serve as a standard reference book in this important and fast growing area of phytochemicals, human nutrition and health