Comparative Effect of Hammer Mill Screen Size and Cell Wall-Degrading Enzymes During Olive Oil Extraction.

The influence of hammer mill screen size (4.5 and 8.5 mm) and enzyme addition (control and 500 ppm) on olive fruit cell wall breakdown and its consequences in terms of oil recovery and the phenolic content of olive oil was studied at the laboratory scale for "Arbequina" and "Koroneiki" at two different maturities. Water recovery and water-soluble carbohydrates in olive paste after malaxation were measured as an indicator of cell wall breakdown. Smaller screen size and enzymes increase oil recovery for Arbequina with a maturity index of 1.6 (6.3-6.6%); and for Koroneiki at a maturity index of 0.2 (15.0-38%) and 2.6 (1.3-4.3%). For both cultivars, the increase in oil recovery is larger in green fruits compared to more ripe fruit. Water recovery and water-soluble carbohydrates increase with small screen size and the enzyme treatments, even when no increment in oil recovery is observed. The water recovery range was 143-239% for Arbequina and 150-262% for Koroneiki; water-soluble carbohydrate range was 1.8-12.7 g/kg for Arbequina and 0.5-5.4 g/kg for Koroneiki. In general, smaller hammer mill screen size and enzymes increase total phenols in the oil, with a larger difference between control and treatment for green fruit than for the ripe fruit. For Arbequina, increases in total phenol content were in the range of 45-60 and 5-20% at maturity index 1.6 and 3.3, respectively. For Koroneiki, the increases were in the range of 31-121 and 7-9% at maturity index 0.2 and 2.6, respectively. Application of cell wall-degrading enzymes improves the cell wall breakdown caused by hammer mill, leading to higher oil recovery and total phenol content. The magnitude of the effect depends on the cultivar and olive fruit maturity.

Study of the minor fraction of virgin olive oil by a multi-class GC-MS approach: Comprehensive quantitative characterization and varietal discrimination potential.

For the first time, a multi-class GC-MS method was applied to perform the quantitative-profiling of the minor fraction of VOOs (considering >40 compounds) in a single run. This comprehensive methodology has demonstrated a remarkable profiling ability on five groups of compounds (phenolic and triterpenic compounds, tocopherols, sterols and free fatty acids) with wide range of polarities/volatilities and chemical entities. After the complete analytical validation of the method, 32 VOO samples from eight different cultivars (some of them very scarcely studied before) were analyzed and the quantitative results were subjected to both non-supervised and supervised multivariate statistics for testing the capability of the determined VOO minor compounds to discriminate the varietal origin of the samples. Typical compositional profiles were defined for each cultivar and promising potential varietal markers were pointed out. The models built to discriminate Cayon and Maurino samples from the rest exhibited the best quality parameters. The relative levels of tocopherols together with characteristic concentration of luteolin, ß-sitosterol and tyrosol were, for instance, the most specific features of Cayon VOOs.

Impact of Microclimate on Fatty Acids and Volatile Terpenes in "Kerman" and "Golden Hills" Pistachio (Pistacia vera) Kernels.

Pistachio is an economically important nut crop in California. Since temperature variations among geographical locations can influence biochemical processes during fruit development, it is of great relevance to understand the impact of growing area over the components that define the nutritional and sensory characteristics of pistachio nuts. Changes in moisture, fat content, fatty acid composition and volatile terpenes were studied during kernel development for "Kerman" and "Golden Hills" varieties in two different California Central Valley microclimates, Lost Hills and Parlier. Moisture content decreased from July to September for both cultivars at both locations. Kerman had a higher moisture content at both locations compared with Golden Hills. Harvest time affected fat content only for Kerman, where the values increased drastically from 21-July to 4-Aug, then remained constant. Golden Hills' fat content remained constant during the period of the study. The main fatty acid in pistachio oil is oleic acid (46% to 59%), followed by linoleic acid (26% to 36%) and palmitic acid (11% to 16%). C16:0, C16:1, C18:2, and C18:3 decreased with harvest time, while C18:1 increased. α-Pinene was the most concentrated volatile among the cultivars and locations. It decreased with harvest time for both cultivars at both locations, ranging from 105 to 2464 mg/kg. At harvest, Golden Hills and Kerman at Parlier both had higher concentrations of α-pinene than the two cultivars at Lost Hills. Our results demonstrate that microclimate affects biosynthesis of fatty acids and terpenes in pistachio kernels, the main compounds responsible for pistachio nutritional and sensory characteristics.

Near-Infrared (NIR) Spectrometry as a Fast and Reliable Tool for Fat and Moisture Analyses in Olives.

The evaluation of fat and moisture contents for olive fruits is crucial for both olive growers and olive oil processors. Reference methods, such as Soxhlet extraction, used for fat content determination in olive fruits are time- and solvent- consuming and labor intensive. Near-infrared (NIR) spectroscopy is proposed as a solution toward rapid and nondestructive analyses of olive fruit fat and moisture contents. In the present work, comparative studies of the fat and moisture quantification methods were performed on four cultivars (Arbosana, Arbequina, Chiquitita, and Koroneiki) during six different harvesting time points to determine the potential of NIR as an alternative methodology. The impact of olive paste crushing degree on NIR performance was also investigated using three different grid sizes (4, 6, and 8 mm) on a hammer mill, in addition to a blade crusher. Results indicate a satisfactory correlation between the reference Soxhlet and NIR methods with R 2 = 0.995. A comparison study of moisture content was also done on NIR and the use of conventional oven with the R 2 value of 0.995. The crushing blade produced higher values in both moisture and fat contents in comparison to the hammer mill. The evaluation indicates that when building a chemometric model, all crush sizes and blade sizes should be represented in the model for highest accuracy.

Deep insight into the minor fraction of virgin olive oil by using LC-MS and GC-MS multi-class methodologies.

Several analytical methods are available to evaluate virgin olive oil (VOO) minor compounds; however, multi-class methodologies are yet rarely studied. Herewith, LC-MS and GC-MS platforms were used to develop two methods capable of simultaneously determine more than 40 compounds belonging to different VOO minor chemical classes within a single run. A non-selective and highly efficient liquid-liquid extraction protocol was optimized for VOO minor components isolation. The separation and detection conditions were adjusted for determining phenolic and triterpenic compounds, free fatty acids and tocopherols by LC-MS, plus sterols and hydrocarbons by GC-MS. Chromatographic analysis times were 31 and 50 min, respectively. A comparative assessment of both methods in terms of analytical performance, easiness, cost and adequacy to the analysis of each class was carried out. The emergence of this kind of multi-class analytical methodologies greatly increases throughput and reduces cost, while avoiding the complexity and redundancy of single-chemical class determinations.

Impact of industrial hammer mill rotor speed on extraction efficiency and quality of extra virgin olive oil.

Crushing is a key step during olive oil extraction. Among commercial crushers, the hammer mill is the most widely used due to its robustness and high throughput. In the present work, the impact of hammer mill rotor speed on extraction yield and overall quality of super-high-density Arbosana olive oils were assessed in an industrial facility. Our results show that increasing the rotor speed from 2400rpm to 3600rpm led to a rise in oil yield of 1.2%, while conserving quality parameters. Sensory analysis showed more pungency with increased rotation speed, while others attributes were unaffected. Volatile compounds showed little variation with the differences in crusher speed; however, total phenols content, two relevant secoiridoids, and triterpenoids levels increased with rotor speed. Hammer mill rotor speed is a processing variable that can be tuned to increase the extraction efficiency and modulate the chemical composition of extra virgin olive oil.