I. Neeman

Avocado oil production and chemical characteristics

Centrifugal force separation is a relatively new industrial process for extracting avocado oil. This study examined the influences of temperature, pH and NaCl concentration on oil extraction efficiency by centrifugal processing. Optimal separation conditions occurred at 75 C, with a pH of 5.5 and NaCl concentration of 5%.Differences in chemical characteristics exist between avocado oils produced by industrial processes and those oils that were produced in the laboratory by organic solvent extraction. The highest amount of chlorophyll, 192.9 ppm, was obtained by ethanolic extraction in the laboratory. Unsaponifiables content reached 1.95% in industrial oil produced by organic solvent extraction. The highest acid value, 8.35, was obtained from industrial oil produced by centrifugal separation. Hydroxyl values in our oils were found to be 2–3 times higher than those reported in the literature.

Diverse effects of ascorbic acid and palmitoyl ascorbate on Helicobacter pylori survival and growth

Among many antioxidants used in the food, pharmaceutical and cosmetic industries, ascorbic acid (AA) is one of the most important. AA has been suggested to decrease the risk of gastric disease (gastritis, duodenal ulcer, and carcinoma) by direct action on Helicobacter pylori. However, there are limited studies on the possible role of AA and its derivatives such as palmitoyl ascorbate (PA) on the growth and survival of H. pylori. In the present study it was demonstrated in vitro that AA in the concentration range 10-20 mg x ml(-1) (50-100 mM) inhibited H. pylori growth in liquid medium under microaerophilic conditions. In contrast, under aerobic conditions AA in the concentration range 2-20 mg x ml(-1) (10-100 mM) significantly increased the survival of H. pylori presumably eliminating the toxic effect of reactive oxygen species on bacterial cells. The hydrophobic derivative of AA, PA (a food antioxidant), demonstrated a strong antibacterial effect, under both aerobic and microaerophilic conditions in the concentration range 0.04-0.4 mg x ml(-1) (0.1-1.0 mM). This effect was also tested on other bacterial strains: Escherichia coli, Proteus vulgaris, Proteus mirabilis, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Clostridium sporogenes and Campylobacter jejuni. Among these bacterial strains, PA showed a similar inhibitory effect on B. cereus and B. subtilis as observed with H. pylori. The results suggest that PA may be considered an important AA derivative in eradication of H. pylori in vitro and in vivo and to decrease the risk for gastric diseases.

Oxidative stability of avocado oil

This study is concerned with the extent of oxidative deterioration and oil stability as determined by measuring peroxide and conjugable oxidation products (COP) values and AOM time of refined bleached avocado oil in comparison with refined soybean and olive oil. The formation of peroxides in avocado oil exposed to daylight at room temperature is similar to that of soybean oil but greater than that of olive oil. No differences were found in peroxide formation, oxodiene values and COP values between the tested oil stored in the dark, at 60 C and at room temperature. The COP ratio in oils stored at 60 C is similar for avocado and olive oil, but differs from that of soybean oil.The AOM stability time both for refined avocado and soybean oil was approximately 14 hr, and for refined olive oil was 15 hr.The extent of oxidative stability of crude avocado oil was determined by measuring peroxide value compared with crude olive oil. Crude avocado oil is very sensitive to oxidation when exposed to daylight and fluorescent light, in contrast to its stability in the dark at room temperature. The chlorophyll content in crude avocado oil is reduced rapidly on exposure to daylight and fluorescent light.

Antioxidant properties of deferoxamine

Deferoxamine, a natural trihydroxamate, was tested for its antioxidant properties. A significant antioxidant effect was detected in linoleic and linolenic acid suspensions, as well as in linoleic acid and fish oil emulsions. Its antioxidant activity was compared to that of butylated hydroxyanisole (BHA) and quercetin. In both emulsions and suspensions, the antioxidant effect of deferoxamine was in the same concentration range of BHA and quercetin. The antioxidant effect of deferoxamine in emulsions was lower than that of BHA. The effect of 0.770 mM deferoxamine in suspensions was the same as that of 0.555 mM BHA. Deferoxamine antioxidant activity in these systems was independent of its capability to bind iron. Inhibition of β-carotene degradation in linoleic acid-Tween 40 emulsion was lower than that of BHA. Deferoxamine inhibited the activity of soy lipoxygenase. The inhibition of lipoxygenase was reversible, but its mechanism is still unknown.

A simple and sensitive method for detecting avocado seed oil in various avocado oils

The presence of avocado seed oil in various avocado oils was detected by thin-layer chromatography (TLC). An unsaponifiable compound, called Component-C, was identified in the avocado seed oil. This compound is unique to avocado seed and has a blue color when developed on the TLC plate. At least 9.2 μg of avocado seed unsaponifiables were needed at a single TLC spot to detect the unique blue color definitely. Admixtures of as little as 0.16% avocado seed oil in various avocado oils can be detected by the proposed procedure.

Effectiveness of antioxidants in refined, bleached avocado oil

The addition of antioxidants propyl gallate (PG), α-tocopherol and ethoxyquin at a level of 250 ppm to refined, bleached avocado oil resulted in the retardation of the oxidative deterioration of the oil when it was stored in the dark at room temperature, exposed to daylight at room temperature (on the shelf) and at 60 C.The extent of oxidation was followed by measuring the peroxide and anisidine values and oil color. Ethoxyquin and α-tocopherol were relatively ineffective antioxidants, whereas PG greatly improved the stability of avocado oil stored in the dark at 60 C, but not in oil exposed to daylight.

Lipolytic activity of white pepper powder at high temperatures in a nonaqueous system

White pepper is added as a spice to goose fat in the food industry (particularly in the liver pâte industry) and causes the development of undesirable flavors. In the present study, we demonstrate that white pepper exhibits lipolytic activity when reacted with goose fat in a hydrophobic system. Temperature and pH dependence measurements suggested that two enzymes or isoenzymes with optimal temperatures at 55 and 85°C, and with optimal pH at 7 and 9, are involved. Wet sterilization of the white pepper irreversibly inactivates its lipolytic activity. Dehydration, destroyed while remoistening, recovered the catalytic activity of the pepper. The reaction obeys classical Michaelis-Menten kinetics at 85°C.