Protective effect of ascorbic acid against the browning developed in apple fruit treated with high hydrostatic pressure

Apple Reineta variety was used as an apple dessert. The 1-1.5-cm cubes were immersed in a sucrose solution (30% w/v) and subjected to high pressure (HP) of 400 MPa for 30 min at 5°C. Different ascorbic acid concentrations were used to protect the fruit from the browning developed after the HP treatment. After 2 months of storage at 5°C, no brown color was observed in the samples treated with 20 mM ascorbic acid, and they were acceptable to consumers. However, untreated samples presented fermentation, and they were not acceptable to consumers. The electric conductivity and potassium content were found to be good indicators of the metabolites released from the fruit to the solution in samples treated with high pressure. HP did not affect the peroxidase activity but eliminated the microbial population.Peer Reviewe

Biological response of rats fed with tofu treated with high hydrostatic pressure

Emerging technologies for food preservation have arisen in recent years, such as high-pressure (HP) hydrostatic treatment, and the biological response for this kind of food preservation is not well-known. Forty female rats (six weeks old) were used in the experiment to evaluate the biological effects of HP treatment of tofu. The animals were divided into groups that were fed with tofu (untreated), tofu treated with HP, and conventional food (as control) for 28 days. The glucose level, mineral content (calcium, potassium, zinc, and magnesium), shinbone maximum shear force, weight of the body, and weight of organs (heart, liver, spleen, and kidneys) were analyzed. The biological response for the rats was that significant differences were found in the calcium amount determined on the serum of the rats fed with untreated tofu and those fed with tofu treated with HP, and the calcium amount was lower on the rats fed with tofu treated with HP. Also, there were significant differences in the weight of the liver, and it was lower in the rats fed with tofu treated with HP. It was quite remarkable how the weight of the body and organs were smaller in the rats fed with tofu in comparison to the weight of the control rats. In the other components assayed no significant differences were found. HP produces a potential effect on tofu as it is observed in the rats response to the tofu treated with HP.Peer Reviewe

High hydrostatic pressure effects on vegetable structure

Cryo-fracture scanning electron microscopy revealed the changes that cauliflower and spinach leaves undergo after treatment with high hydrostatic pressure. High pressure changed cell permeability and enabled movement of water and metabolites from inside to outside of the cell. The ultrastructure showed that parenchyma organization disappeared in spinach leaf and cavity formation occurred after treatment. However, cauliflower exhibited a firm structure with a soaked appearance and would be more suitable than spinach for high hydrostatic pressure treatment.The authors are grateful to The CSIC, project ALI94-07786-C02-01, Madrid, Spain, for financial support.Peer reviewe

Response of rats to intake of tofu treated under high-pressure

As searching continues for an answer as to how products treated under HP could affect the health of human beings, this work has focused on the differences between three types of diets (control, untreated and treated tofu under HP) on a total of 30, 12-week-old, Wistar Hannover female rats. Different assays were carried out and the results showed that the increase in body-weight in the rats fed with tofu diets was significantly lower (P ≤ 0.05) than control, but no significant differences were found between both tofu diets. The weights of the organs of rats (liver, spleen and kidneys) fed with both tofu diets were lower than control rats, but were lowest in those fed with a treated tofu diet. The concentration of metal ions (Ca2+, Mg2+, K+, Zn2+ and Fe2) in the serum in both tofu diets showed an increase in magnesium, potassium and iron, but iron increased more in the treated tofu diet. No differences were found in the shear-force of shinbone. The concentration of glucose, total proteins and albumin decreased and uric acid, bilirubin and alkaline phosphatase increased in rats fed with tofu diets as compared to control rats. Alkaline phosphatase activity was significantly elevated in both tofu diets and a significant difference (P ≤ 0.05) was found between both tofu diets. Cholesterol, HDL-cholesterol and LDL-cholesterol were lower in animals fed with tofu diets and significant differences were found in total cholesterol and LDL-cholesterol between control and tofu diets. The triglycerides and HDL-phospholipids were also lower in the tofu diets. The final results revealed that, in general, it seems that tofu treated under high pressure is not harmful to health. However, some significant differences occurred in rats fed with both tofu diets in comparison to the control diet, but only the activity of alkaline phosphatase presented significant differences (P ≤ 0.05) between untreated and treated tofu diets. © 2002 Elsevier Science Ltd. All rights reserved.Peer Reviewe

Soybean vegetable protein (tofu) preserved with high pressure

Tofu is a soybean vegetable protein that Asians have long consumed; its intake is increasing in other countries. Tofu was purchased at a local shop. The tofu samples were already preserved in plastic bags subjected to vacuum and storage (5 °C). Tofu samples were subjected to high pressure (HP) of 400 MPa at 5 °C for 5, 30, and 45 min. Microbial analysis, sensorial evaluation, and structure were determined. HP treatment in tofu reduces the microbial population. Most of the microorganisms found in the initial population belonged to the Enterobacteriaceae family, bacteria Gram-negative (no Enterobacteriaceae), and bacteria Gram-positive. After HP treatment, Hafnia alvei and Bacillus cereus were found. After HP treatment, tofu is a pasteurized product, which is safer in terms of secondary pathogenic microbial contamination. Sensorial test results revealed that treated tofu was acceptable to consumers. The micrographs on the cryofracture observed with a cryoscanning electron microscope revealed a more compact structure after pressure compared with that of untreated samples, but the aggregates in the treated samples were more disperse.Peer Reviewe

Fruit preservation under high hydrostatic pressure

This study was designed to present a fruit-dessert preserved with high hydrostatic pressure. Enzymatic browning reactions in some fruits and vegetables appear to be activated by pressurization. High hydrostatic pressure extents the shelf-life of fruits decreasing microbial population. Colour in fruits is one of the attributes that produces a deleterious effect after HP treatment. Melon is a good product to be preserved with HP without any pre-treatment. Ascorbic acid concentrations between 10-20 mM prevent the browning. The final product was acceptable to consumers and the shelf life of the fruit-dessert was several weeks longer whereas the control sample fermented.Peer Reviewe