Fortified Cold-Pressed Oils: The Effect on Sensory Quality and Functional Properties

Improving the functionality of virgin and cold-pressed edible vegetable oils: Oxidative stability, sensory acceptability and safety challenges

In recent years, there has been a growing demand for minimally processed foods that offer health benefits and premium sensory characteristics. This trend has led to increased consumption of virgin (VOs) and cold-pressed (CPOs) oils, which are rich sources of bioactive substances. To meet consumer needs for new oil products conferring multi-functional properties over a longer storage period, the scientific community has been revisiting traditional enrichment practices while exploring novel fortification technologies. In the last four years, the interest has been growing faster; an ascending number of annually published studies are about the addition of different plant materials, agri-food by-products, or wastes (intact or extracts) to VOs and CPOs using traditional or innovative fortification processes. Considering this trend, the present review aims to provide an overview and summarize the key findings from relevant papers that were retrieved from extensively searched databases. Our meta-analysis focuses on exposing the most recent trends regarding the exploitation of VOs and CPOs as substrates, the fortification agents and their form of use, as well as the fortification technologies employed. The review critically discusses possible health claim and labeling issues and highlights some chemical and microbial safety concerns along with authenticity issues and gaps in quality specifications that manufacturers have yet to address. All these aspects are examined from the perspective of developing new oil products with well-balanced techno-, senso- and bio-functional characteristics.

Health Benefits, Antioxidant Activity, and Sensory Attributes of Selected Cold-Pressed Oils

The consumption of cold-pressed oils (CPOs) has continuously increased due to their health-promoting compounds, such as polyunsaturated fatty acid (PUFA), tocopherols, sterols, and polyphenols. This study focused on the estimation and comparison of the physicochemical properties and sensory quality of six CPOs: linseed oil (CPLO), pumpkin oil (CPPO), milk thistle oil (CPMTO), rapeseed oil (CPRO), camelina oil (CPCO), and sunflower oil (CPSO), which are the most popular in the Polish market. These oils were analysed for their fatty acid composition (FAC), their tocopherol, sterol, polycyclic aromatic hydrocarbon (PAHs), water, and volatile matter (WVM) contents, as well as their antioxidant activity (AA) and oxidative stability parameters. Moreover, quantitative descriptive analysis (QDA) was performed to obtain detailed information on the sensory profiles and quantitative data on the CPOs' attributes that affected consumer acceptability and purchase intent. All of the analysed CPOs were rich in PUFA (27.94-68.42%). They were characterised by the different total amounts of health-beneficial compounds, such as tocopherols (TTC = 44.04-76.98 mg/100 g), sterols (TSC = 300-684 mg/100 g), and polyphenols (TPC = 2.93-8.32 mg GA/100 g). Additionally, their AA was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) methods, with results ranging between 185.36-396.63, 958.59-1638.58, and 61.93-119.21 µmol TE/100 g, respectively. However, the deterioration parameters of CPOs, such as peroxide values (PV = 0.24-4.61 meq O2/kg), p-anisidine values (pAnV = 0.39-4.77), acid values (AV = 0.31-2.82 mg KOH/g), and impurity amounts (Σ4PAHs = 1.16-8.76 μg/kg and WVM = 0.020-0.090%), did not exceed the level recommended by the Codex Alimentarius Commission. The obtained results indicated that all of the investigated CPOs are valuable sources of health-promoting bioactive compounds.

Microencapsulation with Different Starch-Based Polymers for Improving Oxidative Stability of Cold-Pressed Hickory (Carya cathayensis Sarg.) Oil

Hickory (Carya cathayensis Sarg.) oil is a nutrient-dense edible woody oil, with its unsaturated fatty acids accounting for more than 90% of total ones, and liable to oxidation spoilage. To efficiently improve its stability and expand its application fields, the microencapsulation of cold-pressed hickory oil (CHO) by the molecular embedding method and freeze-drying technique was performed using malt dextrin (MD), hydroxylpropyl-β-cyclodextrin (HP-β-CD), β-cyclodextrin (β-CD), or porous starch (PS) as a wall material. Two wall materials and/or their CHO microcapsulates (CHOM) with higher encapsulation efficiencies (EE) were selected to carry out physical and chemical characterizations using laser particle size diffractometer, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, derivative thermogravimetry, and oxidative stability tests. Results indicated β-CDCHOM and PSCHOM had significantly higher EE values (80.40% and 75.52%) than MDCHOM and HP-β-CDCHOM (39.36% and 48.32%). The particle sizes of the two microcapsules selected were both widely distributed with their spans being more than 1 µm and a certain degree of polydispersity. Microstructural and chemical characterizations indicated that β-CDCHOM had comparatively stable structure and good thermal stability compared with PSCHOM. Storage performances under light, oxygen, and temperature showed that β-CDCHOM was superior to PSCHOM, especially in terms of thermal and oxidative stability. This study demonstrates that β-CD embedding can be applied to improve the oxidative stability of vegetable oils such as hickory oil and act as a means of preparing functional supplementary material.

Effects of the Chemical Composition on the Antioxidant and Sensory Characteristics and Oxidative Stability of Cold-Pressed Black Cumin Oils

The antioxidant capacity (AC); amounts of tocopherols, sterols, and polycyclic aromatic hydrocarbons; oxidative parameters; fatty acid composition (FAC); and sensory quality of cold-pressed black cumin oils (CPBCOs) available on the Polish market were analyzed and compared. The AC levels of the CPBCO samples were determined using four assays, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH = 226.8−790.1 μmol TE/100 g), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS = 385.9−1465.0 μmol TE/100 g), cupric-reducing antioxidant capacity (CUPRAC = 975.3−19,823.3 μmol TE/100 g), and Folin−Ciocalteu assays (FC = 168.1−643.7 μmol TE/100 g). The FAC scores were typical for black cumin oil, except for the sample CPBCO4, which had a higher content of α-linolenic acid (C18:3 = 23.33%), pointing to possible oil adulteration. Additionally, the concentrations of total sterols (TSC = 372 mg/100 g) and tocopherols (TTC = 42.3 mg/100 g) in this sample were higher than those for other investigated oils (TSC = 159−222 mg/100 g, TTC = 1.9−10.4 mg/100 g respectively). The oxidative stability levels (IP = 8.21−37.34 h), peroxide values (PV = 21.36−123.77 meq O2/kg), acid values (AV = 6.40−22.02 mg KOH/kg), and the sums of four specific polycyclic aromatic hydrocarbons (∑4PAHs = 4.48−46.68 μg/kg) in the studied samples differed significantly (p < 0.05). A sensory lexicon including 12 attributes was developed and applied for the sensory evaluation of oils using a quantitative descriptive analysis (QDA).

Analytical Methods and Application of Separation Techniques in Food Science

Food chemistry is a branch of chemistry that aims to characterize the chemical composition of food products, both qualitatively and quantitatively [...]