by Milena Lambri, Arianna Roda, D. Marco De Faveri – Istituto Enologia e Ingegneria Agro-Alimentare, Università Cattolica del Sacro Cuore, Piacenza
Avocado oil is an excellent food ingredient used in various applications, such as bakery products (both savory and sweet products), for seasoning pre-cooked food, in canned vegetables and, as experienced in the application shown below, in chocolate-based products, in partial substitution of cocoa butter or other vegetable oils. In particular, this ingredient stands out among other lipid matrix products, for its gold color with emerald green reflections, its fruity and sweet scent, characteristics to which polyphenols contribute positively as they give stability, promoting long preservation. In particular, the avocado extra virgin oil used in the test, arriving from a system built directly near plantations in the province of Gitega in Burundi, highlights low acidity and peroxide levels. Data related to the phenomena of primary and secondary oxidation are far below the limit values, as it results from the analytical data shown in table 1. UCLA researches (Center for Human Nutrition in California) show that avocados have more concentration of vitamin E than kiwis, peaches and grapes. The resulting oil also has a triglyceride composition similar to that of olive oil, but has a higher smoke point, about 255° C (208° C for olive oil). In addition, the fatty acid profile of this lipid ingredient shows high levels of monounsaturated fats, normally associated with the traditional Mediterranean diet characterized by a high consumption of olive oil. Laboratory tests indicate that the avocado oil contains about 75% monounsaturated fats, and only 14% saturated fats, rather small percentage. Other positive characteristics are: the content of β-sitosterol (0.5-1.0%) in significantly higher quantity than olive oil and the lowest level of squalene. It is shown that β-sitosterol can relieve symptoms of benign prostate hypertrophia and the equivalent amount referred to as pharmacologically active medicine, may be taken with just 10-15 grams of avocado oil per day. Although the mechanism of action has not yet been clarified, the clinical tests gave positive results confirming its actual effects.
Shelf-life tests of gianduja cream with the addition of avocado oil
Test setting
The study of shelf-life was carried out using Venchi gianduja cream as base matrix. In that matrix the following were added in different percentages:
• avocado oil produced in the last oil campaign in Burundi;
• Extra-Virgin oil from taggiasca olives packed in Imperia.
With these matrices and ingredients the following samples were made:
• A -gianduia cream with 5% avocado oil;
• B -gianduja cream with 8% avocado oil;
• C -gianduja cream with 3% avocado oil and 2% extra-virgin olive oil;
considering as reference sample (D), Venchi gianduja cream already present on the market. All samples were tested at t0 time and subsequently subjected in triplicate to an accelerated aging test, monitoring them after one, three, six, eight and ten days (respectively at t1, t3, t,6t8 t10 time). Therefore, for each sample, analysis of acidity, peroxides and sensory control were carried out on freshly prepared mixture (t0 time), and then repeated at t1, t3, t6, t8, t10 time and then after one, three, six, eight and ten days of preparation. The conditions for accelerated aging have substantiated in the maintenance of the samples in stove at a temperature of 63 ± 1°C, in open beckers (Besbes, 2004).
Results of tests
The number of peroxides and acidity were determining on the lipid matrix extracted from the product. The number of peroxides is linked to the process of rancidity and its determination is essential to evaluate the quality of a lipid matrix. According to Regulation (EEC) n. 2568/91 the number of peroxides varies in olive oils as shown in table 2. The determination of the number of peroxides during the test has given negative results. That is, the analysis carried out on samples taken from the stove after 1, 3, 6, 8 and 10 days from the moment of preparation did not provide any indication related to the presence of compounds resulting from oxidation. Concerning acidity, however, a growing trend over time was found, (figure 1), although contained on levels compatible with the values indicated by law (Reg. EC 1531/2001) for the commercial classification of olive oils (table 3). Finally, each sample taken from the stove was subjected to sensory analysis through a hedonistic and acceptability test. Each product has been assessed both on the day of its collection, and on the immediately following days, during which the beckers were exposed to air at room temperature in order to evaluate their evolution. The two most popular products from a sensory point of view were those containing 5% and 8% of avocado oil, although all have been appreciated by tasters and have kept their sensory profile almost unchanged in various preservation times, proving to be very stable against oxidation and thermal stress.
Concluding remarks
In the case referred to in this survey, we have verified the possibility of using avocado oil, pure or mixed with olive oil, as an ingredient in the production of gianduja chocolate spreadable cream. The results achieved by such application show a high oxidative stability of the cream added with avocado oil, even if maintained in experimental conditions, lasting for several days, with high temperatures and in the presence of oxygen. This may be due to the presence of antioxidant compounds of the oil itself, or to a synergistic effect of the latter with the phenolic compounds of cocoa, bringing out the antioxidant and protective action on the lipid component. From preliminary tests carried out on small volumes it can be said, moreover, that tested avocado oil gives sensory features that distinctly characterize the spreadable cream, even compared to the one containing extra virgin oil from taggiasca olives, currently in use at Venchi S.p.A. Confirmation tests carried out on a larger scale (industrial or semi-industrial) are needed, particularly to provide for proper mixing and tempering stages, which have not been carried out yet under laboratory conditions.
Bibliography
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• Lopez Lledesma R., Frati Munari A.C., Hernandez Dominguez B.C., et al. (1996) Monounsaturated fatty acid (avocado) rich diet for mild hypercholesterolemia. Archives of Medical Research, 27(4):519-23
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• Lu Q.Y., Arteaga J.R., Zhang Q., Huerta S., Go V.L., Heber D. (2005). Inhibition of prostate cancer cell growth by an avocado extract: role of lipid-soluble bioactive substances. Journal of Nutritional Biochemistry, 16(1):23-30
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Figure 1. Samples acidity respectively at t1, t3, t,6t8 t10 time
