Extracted California olive oil

Summary Extracted olive oil is not used exclusively for soapmaking but in fact is used to the utmost extent in edible oils. General processing procedures are outlined for the production of edible olive oil from high acid extracted olive oil.     

Color changes in olive oil

The following is a summary of the conclusions and facts brought out in this investigation:

1. That yellow olive oil packed in tin may turn green, and that this reaction is brought about by reduction of the yellow color through the action of the free fatty acids of the oil on the tinplate.
2. That this reaction will not take place at normal temperatures in the presence of light.
3. That the green color of olive oil, so formed, reverts to yellow by the action of light.
4. That the formation of green color in olive oil is dependent on the acid strength of the oil and depth of the original yellow color and increases proportionately with these.
5. That, in general, most olive oils on the market packed in tin, are of a greenish color, while the bottled product is yellow. This, of course, does not apply to fresh oil, but only that which is sufficiently old to have permitted any color change to have taken place.
6. That it is not possible to pack olive oil in cans without development of greenish color unless the original oil is rendered neutral or bleached. As it is not practical to render the oil absolutely neutral or to bleach it, the formation of green color in tin cannot be entirely prevented in practice but may be controlled to a certain extent.
7. That the development of excessive green color, which might be objectionable, can be prevented either by packing in cans only oil of low acidity (below 0.25%) or oil, the original color of which is light yellow. In the latter case the acidity is of little consequence as far as color is concerned.
8. That green-colored oil in cans can be reconditioned by transferring to bottles and exposing to light, whereby the original yellow color is restored.

     

Pigments present in virgin olive oil

The qualitative and quantitative control of pigments in ripe olives and in extracted virgin olive oil has increased our knowledge of the influence on these compounds in the areas of ripening of the fruit, storage time in the factory and the oil extraction process. As the harvesting time of the fruits increases, pigment content decreases. During storage, the presence of lipoxygenase has been detected, as well as a considerable decrease in chlorophylls and a small decrease in carotenoids. During the extraction process, the chlorophyllic fraction is destroyed in the greater part, and although the carotenoid fraction is also affected, its concentration increases in the oil with respect to that in the fresh fruit. In the pigment degradation, in addition to the acid-catalyzed reaction, the presence of lipoxygenase suggests a role for this enzyme.     

Color-pigment correlation in virgin olive oil

The chlorophyll and carotenoid content of virgin olive oils from five varieties harvested at varying degrees of ripeness were determined. Colors were evaluated from the chromatic ordinates L*, a*, b* of the absorption spectrum. Oil color changes for different varieties or stages of ripeness are directly related to pigment content and a* and b* values. The statistical study made on both series of parameters proves that there is a good correlation between them. The carotenoid content and b* have one of the best correlation coefficients (r) and is easily measured. This methodology evaluates chlorophyll and carotenoid content, an additional attribute for evaluation of virgin olive oil quality.     

Studies in photooxidation of olive oil

Photooxidation of olive oil, bleached to remove most non-triglyceride components, was studied to elucidate the role of added chlorophyll a, pheophytin a and b,α- andβ-carotene, d-α-tocopherol and nickel dibutyldithiocarbamate. Chlorophyll functioned as a photosensitizer resulting in rapid oxidation of the oil and the added components and loss of color.α- andβ-carotene acted essentially equally as singlet oxygen quenchers.α-tocopherol had little apparent effect on the oxidation rate. Carotenes and tocopherols apparently were destroyed more rapidly when chlorophyll was present. The ratio of peroxide value to conjugated dienoic acids formed developed greater values when chlorophyll was present, thus suggesting a singlet oxygen effect in the system. Pheophytin also proved to be an oxidation promoter.     

California apricot oil

Summary The characteristics and the percentages of the fatty acids present in apricot kernel oil as glycerides have been determined. The oil studied was found to contain about 90.6 per cent of unsaturated acids consisting of a mixture of oleic and linoleic acids. The saturated acids amounted to about 3.6 per cent and were composed almost entirely of palmitic and stearic acids. Mention is made of the utilization of the press cake for the recovery of volatile oil, for fertilizer, and as a feed for livestock. An analysis of the press cake is given. A table of the smoking points for various fats and oils by the J. M. McCoy procedure is given for comparison with that of apricot kernel oil. In addition to the established use of the oil by cosmetic manufacturers, other possible outlets include its use as a salad and cooking oil, for the roasting of shelled nuts, and for the manufacture of soap.     

Studies on olive oil standardization

Summary Experiments were conducted in the Research Experiment Station for Agricultural Technology, Athens, Greece, to study the effect of climatic conditions, state of maturity, infection by olive fly, and the effect of various fertilizers upon the quality of olive oil. Olive oil produced in localities where the temperature is low during the maturity period has more unsaturated fatty acids than oil produced in localities with higher temperatures. With the advance of maturity the proportion of unsaturated fatty acids increased. Infection by olive fly had no appreciable effect upon the relative proportion of saturated fatty acids. For studying of the effect of fertilizers the injection method was used. Nitrogen fertilizers injected into the branches gave considerable increase in the volume of fruit, its protein content, and the total amount of oil produced per acre.     

Quality characteristics of olive leaf‐olive oil preparations

Olive leaf‐olive oil preparations were obtained by vigorous mixing at various levels of addition (5, 10, 15%w/w) of new or mature leaves. After removal of the plant material via centrifugation, quality and sensory characteristics of the preparations were determined. Oxidative stability (120°C, 20 L/h) and DPPH radical scavenging were increased ～2–7 fold depending on the level of leaves used due to enrichment with polar phenols, mainly oleuropein, and a‐tocopherol. The extraction process affected the chlorophyll content and organoleptic traits as indicated by acceptability and preference tests (n = 50). Forty‐four % of the panelists identified a strong pungency in preparations with 15% w/w new leaves. Fifty‐four % of them identified a bitter taste in those with 15% w/w mature leaves, which was attributed to high levels of oleuropein (～200 mg/kg oil). Olive leaf‐olive oil preparations had interesting properties regarding antioxidants present that can attract the interest of a functional product market. Practical applications: The wider use of olive oil and derived products is highly desirable. In this sense, the current study presents data that support introduction to the market of a new specialty olive oil based solely on olive tree products (olive oil and leaves). Thus, in addition to olive oil and olive paste, a new product, that is an olive oil enriched with olive leaf antioxidants, especially oleuropein produced via a “green” technique (mechanical means instead of extraction with organic solvent) can be made available for consumers.     

Machines for olive paste preparation producing quality virgin olive oil

Polyphenolic substances enhance the resistance to oxidation of virgin olive oils, but an excess of polyphenols determines a marked bitter, somewhat tannic taste of the oil, similar to the taste of unripe olives. Tests have been carried out on drupes of different cultivars in industrial productions to evaluate the effect of the machines used to prepare olive pastes on the contents of polyphenols in the oils. Notably greater amounts of polyphenols were found in the oils extracted from hammer-crushed pastes than in the oils extracted from milled pastes. The kneading process which follows, especially if it is long, often reduces the amounts of total polyphenols. Therefore, in order to obtain the best organoleptic and chemical quality in extra virgin olive oils, two systems are suggested for the processing procedures. For olives of certain cultivars (Coratina) and for not-blackened or slightly blackened drupes yielding oils with a very high content of total polyphenols, it is most expedient to use the stone-mill together with a kneader system. But it is more suitable to utilize the hammercrusher together with a kneader system in processing olives (such as the Ogiiarola Salentina or Leccino cultivars) yielding normally “sweet” oils with a low content of total polyphenols.     

Characterization of a 13-lipoxygenase from virgin olive oil and oil bodies of olive endosperms

Olive oil is one of the oldest known vegetable oils, and it is almost unique in that it can be consumed without any refining treatment. One of its most important quality problems is oxidative rancidity due to the oxygenation of polyenoic fatty acids and formation of compounds that derive from these fatty acid hydroperoxides. Beside autoxidation, lipoxygenases (LOXs) were suggested to be involved in this process. Here we show, that approximately 1.6% of all linoleic acid (LA) molecules within olive oil samples had been converted into LOX-derived (13S,9Z,11E)-13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE) as determined by ¹H NMR- and HPLC analysis. LOX activity tests indicated the occurrence of an active 13-LOX exhibiting a pH optimum between pH 5.5 and 6.0. Furthermore, this enzyme preferentially metabolized free fatty acids. In order to elucidate the origin of this LOX, we analyzed olive endosperms for LOX forms. Chromatography of total protein extracts of the tissue showed LOX activity almost exclusively associated with a high molecular mass fraction. Light microscopic inspection, as well as the calculated phosphate, neutral lipid, and protein content of this fraction, suggested that this fraction may contain oil bodies and that LOX activity was associated with their membrane. This LOX activity had a pH optimum of 6.0. Activity assays at various temperatures indicated a significant catalytic efficiency of the enzyme up to 55°C. HPLC analysis of LA oxygenation products within the lipid fraction and of activity tests of isolated oil bodies showed that the LOX present in mature olive endosperm oil bodies was, as the enzyme from olive oil, a linoleate 13-LOX preferentially active on free LA. We suggest, that this oil body LOX from olive endosperm, is the one detected originally in olive oil and may survive at least in part olive oil production.