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

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