Enzymes and food flavor‐A review

The use of enzymes in flavor generation in food technology is reviewed. In the first part, important products derived from natural macromolecules present in foods such as fats, proteins, nucleic acids and flavor precursors are discussed in terms of the enzymes involved in the reactions and the relation of the products with flavor. Enzymes that are used to eliminate natural or process induced off‐flavors are also discussed. In the second part, the use of enzymes for the direct synthesis of flavoring compounds is presented.     

Sorption behavior of charged and neutral polar organic compounds on solid phase extraction materials: which functional group governs sorption?

Numerous polar anthropogenic organic chemicals have been found in the aqueous environment. Solid phase extraction (SPE) has been applied for the isolation of these from aqueous matrices, employing various materials. Nevertheless, little is known about the influence of functional groups on the sorption of the solutes onto these materials. Therefore, the sorption interactions of (charged) polar organic solutes to neutral (HLB), cation-exchanging (MCX, WCX), and anion-exchanging (MAX, WAX) OASIS polymers have been studied. For neutral solutes HLB has the highest capacity and affinity. Van der Waals interaction, rather than hydrogen bonding, appears to be the predominant factor determining sorption. For charged molecules, MCX and MAX show by far the highest affinity and capacity. Adsorption is already efficient at low concentrations and the maximum sorption capacity equals the amount of charged functional groups on the material. The results from this study allow semiquantitative predictions if a solute will adsorb on one of the OASIS materials and which functional groups govern adsorption.     

Analysis of patulin in apple products by liquid–liquid extraction,solid phase extraction and matrix solid-phase dispersion methods: a comparative study

Patulin is a marker of quality in the apple and apple juice industry and due to the potential risk for human health, reliable and potential methods for extracting patulin from a sample are therefore needed. In this study, the three methods with liquid–liquid extraction, matrix solid-phase dispersion (MSPD) and with solid-phase extraction (SPE) were studied for extracting patulin from different apple products. Result showed that for AJC and apple sample, MSPD method is most suitable for extracting patulin among the three methods. The recovery rates of AJC and apple sample were 80.35–114.46 and 79.68–94.32%, respectively, the coefficient variations were 3.18–4.90%; For dilute juice, SPE procedure is suitable for analysis of patulin and the recovery rates were and 85.35–90.14%.     

Relationship between pungency and food components – A comparison of chemical and sensory evaluations

The influence of food ingredients (water, starch, fat, and sugar), individually and in combination, on the sensory perception of the pungency of capsaicin was studied in model food systems using the time-intensity method. Furthermore, the transferability of the results obtained using model food matrices to complex matrices, such as convenience salsas, was investigated. Significant differences between the samples (p < 0.05) were examined by analysis of variance (ANOVA) followed by the Tukey-HSD post hoc test. A highly complex matrix and a high starch content reduced the perception of pungency in both the model food matrices and the convenience salsa products. Therefore, the time-related maximum intensity of pungency (I_max) was affected by other factors in addition to the capsaicin concentration.The total capsaicinoid content in the salsas was quantified by high-performance liquid chromatography–mass spectrometry (HPLC–MS) and correlated to the results of the sensory evaluation. The best correlation (R² = 0.8029) was observed for the total capsaicinoid content and the maximum intensity of pungency (I_max) in comparison to the duration of the total pungency perception T_Dur (R² = 0.5176) and the area under the curve (R² = 0.6898). The calculated regression models serve as an example of how empirical calculations can be generated and used in a specific context.     

Pressurized aqueous ethanol extraction of β-glucans and phenolic compounds from waxy barley

Beta-glucans and phenolics were extracted from waxy barley using pressurized aqueous ethanol in a stirred batch reactor at 25 bar and 500 rpm. The effect of temperature (135–175 °C), extraction time (15–55 min) and ethanol content (5–20%) was evaluated. Temperature had an opposite effect on the extraction of both compounds. The higher the temperature, the lower the β-glucan extraction yield due to fragmentation, but a significant increase on the phenolic recovery was observed. Long extraction times favored the extraction of β-glucans at low temperatures and phenolics at any temperature. The ethanol content was not statistically significant on the β-glucan extraction, but helped to maintain the molecular weight of the extracted β-glucan. To obtain liquid extracts rich in high molecular weight β-glucans and phenolics, mild conditions of 151 °C, 21 min and 16% ethanol are needed, leading to 51% β-glucan extraction yield with a molecular weight of 500–600 kDa and 5 mg GAE/g barley.     

Extraction and purification of free cholesterol from some egg-containing food by on-line supercritical fluid extraction – solid-phase extraction

Two methods for the extraction and determination of free cholesterol in some egg-containing food samples were compared: the classical Soxhlet method and a supercritical carbon dioxide extraction (at 338 bar and 40vv°C) coupled on-line with solid-phase extraction (SPE with a solid trap packed with an ODS stationary phase). Egg noodles, biscuits and sweet snacks were homogenised and added to the internal standard and anhydrous sodium sulphate. Part of each sample was extracted by on-line supercritical fluid extraction - solid-phase extraction (SFE-SPE) and the remaining part was extracted by the classical method using petroleum ether. A further purification after the Soxhlet extraction was performed by SPE. Free cholesterol was determined in both the off-line Soxhlet-SPE fraction and the on-line SFE-SPE extract with capillary gas chromatography after silylation. The two extraction methods gave similar results. However, on-line SFE-SPE represents a valid alternative to the Soxhlet method because it shows important advantages, such as a short analysis time and low solvent consumption.     

The biogenesis of food‐related Pyrazines

Abstract

Biogenetically formed pyrazines are important flavor compounds in view of the current industry trend toward all‐natural flavors in foods. Food‐related pyrazines are reviewed and summary data are used as a basis to discuss possible chemical and biochemical mechanisms for their formation.     

An overview of binary taste–taste interactions

The human gustatory system is capable of identifying five major taste qualities: sweet, sour, bitter, salty and savory (umami), and perhaps several sub-qualities. This is a relatively small number of qualities given the vast number and structural diversity of chemical compounds that elicit taste. When we consume a food, our taste receptor cells are activated by numerous stimuli via several transduction pathways. An important food-related taste question which remains largely unanswered is: How do taste perceptions change when multiple taste stimuli are presented together in a food or beverage rather than when presented alone? The interactions among taste compounds is a large research area that has interested electrophysiologists, psychophysicists, biochemists, and food scientists alike. On a practical level, taste interactions are important in the development and modification of foods, beverages or oral care products. Is there enhancement or suppression of intensity when adding stimuli of the same or different qualities together? Relevant psychophysical literature on taste–taste interactions along with selected psychophysical theory is reviewed. We suggest that the position of the individual taste stimuli on the concentration-intensity psychophysical curve (expansive, linear, or compressive phase of the curve) predicts important interactions when reporting enhancement or suppression of taste mixtures.     

Optimization of a solid phase extraction and hydrophilic interaction liquid chromatography–tandem mass spectrometry method for the determination of metformin in dietary supplements and herbal medicines

Metformin is one of the most common adulterants found in anti-diabetic dietary supplements and herbal medicines. An analytical method based on hydrophilic interaction chromatography (HILIC)/tandem mass spectrometry was developed and validated for the determination of metformin in dietary supplements and herbal medicines. Sample preparation involved solid phase extraction of the analyte using Plexa PCX cartridges, and cleanup by a primary–secondary amine (PSA) adsorbent for minimization of the matrix effect. Chromatographic separation was performed on a HILIC column using a mixture of 0.025 mol/L ammonium formate (pH 3) and acetonitrile (18:82, v/v) as the mobile phase at flow rate of 0.25 mL/min. The method was validated in four matrices (capsules, honeyed pills, tablets and oral solutions). The method had a good linear range (5–500 ng/mL), and the overall precision and accuracy ranged from 2.2% to 9.9% and 4.6% to 11.3%, respectively.     

Metal–organic framework for the extraction and detection of pesticides from food commodities

Pesticide residues in food matrices, threatening the survival and development of humanity, is one of the critical challenges worldwide. Metal–organic frameworks (MOFs) possess excellent properties, which include excellent adsorption capacity, tailorable shape and size, hierarchical structure, numerous surface-active sites, high specific surface areas, high chemical stabilities, and ease of modification and functionalization. These promising properties render MOFs as advantageous porous materials for the extraction and detection of pesticides in food samples. This review is based on a brief introduction of MOFs and highlights recent advances in pesticide extraction and detection through MOFs. Furthermore, the challenges and prospects in this field are also described.     

Interference-free simultaneous determination of Sudan dyes in chili foods using solid phase extraction coupled with HPLC–DAD

A simple, rapid, inexpensive and robust solid phase extraction (SPE) cleanup method coupled with high performance liquid chromatography–diode array detector (HPLC–DAD) for the determination of four Sudan dyes in chili products was developed. The interference substances were removed completely by normal SPE-Alumina N, resulting in a clean and interference-free baseline. Without the use of expensive LCMS/MS instrument the low levels of Sudan dyes were identified and quantified in chili foods with good precision and recovery. Depending on the Sudan dyes involved, the limit of determination (LOD) and limit of quantification (LOQ) were in the range of 4.1–5.8 and 13.2–19.1 μg/kg, respectively. The recovery, repeatability and reproducibility varied from 93.2% to 103%, from 0.3% to 4.4%, and from 0.6% to 4.9%, respectively. This method is suitable for the routine analysis of Sudan dyes for the common factory laboratory due to its sensitivity, simplicity, convenience and low-cost.     

Determination of alkylphenol residues in breast and commercial milk by solid-phase extraction and gas chromatography–mass spectrometry

This study presents a feasible and sensitive method to determine alkylphenol residues (i.e., 4-t-octylphenol (4-t-OP) and the isomers of 4-nonylphenols (4-NPs)) in breast milk samples and commercial cow milk products. The matrix interference associated with the constituents in the milk was reduced by extraction with n-hexane and dilution with 50% methanolic solution (v/v, methanol/water), then followed by the Oasis-HLB SPE extraction. The analytes were determined by a GC–MS system in full-scan and selected ion monitoring modes simultaneously. Limit of quantitation was less than 0.05 ng/g in a 20 g (wet weight) milk sample. The 4-NPs were detected in 19 of the 20 breast milk samples at concentrations ranging from 1.7 to 11.6 ng/g, while 4-t-OP was detected in 8 samples at concentrations ranging from 0.4 to 1.1 ng/g. The 4-NPs were detected in all the testing commercial cow milk products at concentrations ranging from 2.9 to 8.8 ng/g.     

Changes in physico‐chemical and rheological properties of rice during flaking

Hydration, solubility, pasting and rheological properties of roasted‐parboiled rice and flakes were examined in comparison to raw rice. There was an increase in the hydration capacity, swelling power and solubility during roasting‐parboiling of rice as a result of gelatinization of its starch. Flaking caused further increase due to damage of starch by application of mechanical force. The changes were higher in flakes from roller‐flaker as compared to those from edge‐runner. Pasting characteristics of flour slurries in Rapid Visco Analyzer showed a typical profile for pregelatinized products viz. a higher initial viscosity but a lower peak viscosity for roasted‐parboiled rice and flaked rice than for raw rice. The viscosity curves and flow curves of the products over a wide range of shear rate indicated a non‐Newtonian, pseudoplastic behaviour for all the samples. All samples showed typical hysteresis loop in their viscosity curves indicating their thixotropic nature. Flakes from roller‐flaker exhibited lower viscosity but more thixotrophy indicating higher starch breakdown in them than in edge‐runner flakes, which seemed to have more of heat damaged starch.     

Functional implications of bound phenolic compounds and phenolics–food interaction: A review

Sizeable scientific evidence indicates the health benefits related to phenolic compounds and dietary fiber. Various phenolic compounds-rich foods or ingredients are also rich in dietary fiber, and these two health components may interrelate via noncovalent (reversible) and covalent (mostly irreversible) interactions. Notwithstanding, these interactions are responsible for the carrier effect ascribed to fiber toward the digestive system and can modulate the bioaccessibility of phenolics, thus shaping health-promoting effects in vivo. On this basis, the present review focuses on the nature, occurrence, and implications of the interactions between phenolics and food components. Covalent and noncovalent interactions are presented, their occurrence discussed, and the effect of food processing introduced. Once reaching the large intestine, fiber-bound phenolics undergo an intense transformation by the microbial community therein, encompassing reactions such as deglycosylation, dehydroxylation, α- and β-oxidation, dehydrogenation, demethylation, decarboxylation, C-ring fission, and cleavage to lower molecular weight phenolics. Comparatively less information is still available on the consequences on gut microbiota. So far, the very most of the information on the ability of bound phenolics to modulate gut microbiota relates to in vitro models and single strains in culture medium. Despite offering promising information, such models provide limited information about the effect on gut microbes, and future research is deemed in this field.     

Diagonal or vertical? An empirical study of the impact of food brand logo orientation on consumers’ food perception and food attitude

This study explores the role of food brand logo orientation on consumers’ perceptions and attitudes regarding food products through four studies. Study 1 examines the effects of food brand logo orientation (diagonal vs. vertical) on consumer perceptions of food tastiness and risk. The findings suggest that diagonal (vs. vertical) food brand logos result in higher (lower) taste and risk perception in branded food. Study 2 reveals the underlying mechanisms of this effect by introducing perceived movement as a mediator between logo orientation and food perception. The results support the inference that movement is an underlying mechanism for the effect. Study 3 examines the effects of brand logo orientation and regulatory focus on consumer attitudes regarding branded food. The results suggest that for consumers with a promotion focus, a diagonal (vs. vertical) oriented logo leads to a more favorable attitude toward the food. For consumers with a prevention focus, a diagonal (vs. vertical) oriented logo leads to a less favorable attitude toward the food. Study 4 establishes validity of the above findings regarding native English speakers.     

Color and chemical stability of tea polyphenol (−)-epigallocatechin-3-gallate in solution and solid states

(−)-Epigallocatechin-3-gallate (EGCG), the main component with the highest biological activity in green tea, has been extensively studied for its activities and degradation behaviors in infusions and solutions. However, neither the characterization of its degradation products in solutions, nor its color degradation and stability in the solid state are well documented. Therefore, in this present study, the color and chemical stability of EGCG in solutions with various concentrations ranging from 0.05 mg/mL to 30 mg/mL and in the solid state following storage at 0% and 85% relative humidity (RH), 80 °C were investigated. Color parameters were monitored over time, and the chemical stability was determined using high performance liquid chromatography (HPLC)–diode array detection (DAD) analysis and HPLC–mass spectrometry (MS). Mathematical models for color degradation of EGCG in both solution and solid states were established. The chemical stability of EGCG was found to be affected by its physical state, concentration of reactants, oxygen levels, pH, and RH conditions. Epimerization and oxidation were found to be the two major reactions causing the degradation of EGCG in the solution and solid state, respectively. Major degradation products, catechin monomers and oxidation dimers, were identified. Cleavage products, gallic acid and catechin monomers, were also found. These results further elaborated the degradation mechanisms of EGCG in solutions of varying concentrations and revealed the chemical changes resulting in color degradation of EGCG in the solid state.