At the present time, there does not seem to be any very great need of a by-product industry to utilize waste avocados. Still there is a. certain amount of soft fruit and blemished fruit which normally will find no market in the fresh condition. In order to develop practical methods of utilizing this fruit and any contemplated over production.
Avocado Paste: Since the fruit is used as a salad fruit, the first thought will be to prepare a paste or minced product from the peeled fruit and preserve it by suitable methods. This idea was tested very thoroughly. Paste was treated with varying amounts of salt to preserve it without sterilization. Portions of the same lots were sterilized at various temperatures. Various antiseptics were tried, such as vinegar, or benzoic acid. Fermentation of the paste before canning was also experimented upon.
In all cases, the results were poor because of the loss of the fresh avocado flavor and the development of an acrid taste.
It is possible that if the fruit was treated with lye before making into a paste, the acrid taste would be eliminated. Experiments made on the peeled halves would indicate this to be true.
Dried Avocados: Peeled and pitted fruit was dried at 100 degrees C. The flavor of the dried product was palatable, but very much inferior to the fresh article. Used in soup, it was found to impart a pleasant rich flavor. It seems to have possibilities as a flavoring for high-priced soups. The temperature of drying used should not be above 212 degrees F. The flesh darkens during drying.
Canning Avocados: A number of different lots of fruit were canned in various kinds of brines and syrups and at various temperatures. Salt brines were unsatisfactory in all cases. A disagreeable acrid taste develops in the fruit canned in plain water or brines of various degrees of salt.
Fruit canned in a 60 per cent cane sugar syrup at 180 degrees F gave excellent results. The flavor was rich and seemed equal to that of the fresh fruit. The only objection seems to be that the flavor is a little too rich for the product to be eaten freely. Fruit sterilized in a syrup at 212 degrees F. was not equal to that sterilized at 180 degrees F. The addition of a small amount of lemon juice to the syrup improved the flavor of the canned product.
Syrups of lower concentration than 60 per cent were not so satisfactory as the heavy syrup.
Preservation in Vinegar and in Brandy: The fruit keeps well if stored in ordinary cider vinegar, but the excess vinegar must be leached out before using the fruit. This flattens the flavor considerably, but the product is fairly palatable. The texture becomes soft on long standing.
When stored in brandy of good quality the halved fruit retains its color, texture and flavor very well. The alcohol is easily removed by soaking the fruit in water twenty-four hours before use.
Oil: The avocado is very rich in oil which constitutes a very large portion of the nutritive value of the fruit. It is probable that it will be many years before enough avocados are produced in the state to make possible the establishment of an avocado oil industry. As a point of interest, however, various methods of recovering the oil were tried out on a very small scale. It seemed to be necessary to dry the fruit first. The oil was then recovered by pressure at 500 pounds per square inch and the oil left in the press cake was extracted with ether. The oil obtained by pressure had a pleasing flavor. Its appearance was greatly improved by decolorizing with bone-black and filtration. A great deal of solid fat separates on cooling the oil. This can be removed by filtration. The oil at best was inferior to good cottonseed oil. Therefore, avocado oil as a by-product does not seem very promising for table use. It may later be discovered to have other uses, such as in soap-making.