Impact of Frost on the Morphology and Chemical Composition of cv. Santulhana Olives

Nuno Rodrigues,Rebeca Cruz,Ana I Rodrigues,José Alberto Pereira,Susana Casal,António M Peres

doi:10.3390/app12031222

Abstract

Frost events and extreme weather phenomena greatly affect several characteristics of the olive fruit. This study evaluated the impact of frost on the morphology, composition (moisture, fat, fatty acids, tocopherols, and total phenolic contents), and antioxidant activity of olives of cv. Santulhana. A total of 14 trees from the same geographical region (Santulhão, northeast of Portugal) were chosen, including trees subjected or not subjected to frost conditions (n = 7 each). The results showed that frost led to morphological changes in olive fruits, particularly in terms of weight and diameter, which were imposed by a huge decrease in the moisture content (−20%). Fat relative content increased as a consequence of the water loss (+29% in fresh pulp weight), with a slight reduction of the relative abundance of saturated fatty acids (−4%) and tocopherol contents in the fat (−17%). However, the total phenolic contents and antioxidant activity were severely affected (−70% and −42%, respectively), with potential consequences for the olive oil stability and sensorial attributes. Principal component analysis showed that both morphological and chemical parameters could be used as biomarkers to identify olives subjected or not subjected to frost. The overall negative impact of frost on the minor antioxidant contents of cv. Santulhana olives may anticipate a quality loss of olive oils extracted from olives affected by frost.

Highlights

Olive oil, the main source of fat in the Mediterranean diet, is a food with an exceptional balance between saturated and unsaturated fatty acids, containing other important minor compounds such as polyphenols, tocopherols, carotenoids, sterols, and chlorophylls
Olive fruits can be damaged by frost, i.e., when the air temperature decreases to 0 ◦C or lower, promoting freezing of the fruits’ pulp water, reducing enzymatic and biochemical reactions, as well inhibiting microbial activity [24,25]
The results showed no significant effect of frost on the MUFA and PUFA relative abundance, which is in line with the findings of Asheri et al [29] for olive oils extracted from olives grown at low temperatures

Summary

Introduction

The main source of fat in the Mediterranean diet, is a food with an exceptional balance between saturated and unsaturated fatty acids, containing other important minor compounds such as polyphenols, tocopherols, carotenoids, sterols, and chlorophylls. Later harvest will deliver olives with a higher percentage of oil per mass of the fruit (lower moisture content), increasing the olive oil extraction yield per fruit mass, not necessarily per tree. These olive oils have low bitterness and lack green fruit aromas compared to oils extracted from olives at earlier ripeness stages, showing a shorter shelf-life imposed by a reduction on its natural antioxidants and being, more prone to the appearance of defects such as rancidity [9]. Olive farmers and olive oil producers face a dilemma in establishing the best harvest time-period, which would allow farmers to obtain a satisfactory yield without compromising the olive oil physicochemical quality

Methods

Results

Conclusion