Changes in flavour compound profiles of precooked pork after reheating (warmed‐over flavour) using gas chromatography–olfactometry–mass spectrometry with chromatographic feature extraction

Yeast extracts weakened warmed-over flavor in surimi gels made from silver carp due to the masking effect by high concentrations of pyrazines and esters

Warmed-over flavor (WOF) is an off-flavor in surimi gels. Yeast extract (YE) could improve the aroma properties of food. However, the effect of YE on the WOF in surimi gels and its mechanism was still unclear. In this study, aroma profiles, the composition of aroma compounds and aroma precursors, concentrations of WOF compounds, and thiobarbituric acid reactive substances (TBARS) of surimi gels with different amounts of YE were investigated by molecular sensory science and chromatographic techniques. Moreover, the effect of pyrazines and esters introduced by YE on WOF was also tested by sensory analysis. The addition of no less than 1% YE to surimi gels significantly weakened WOF. However, YE did not decrease the concentrations of WOF compounds and did not change the fatty acid composition and TBARS in surimi gels. Conversely, the addition of YE significantly increased the contents of free amino acids, N-containing compounds, and esters in surimi gels. The contents of total free amino acids, 2,6-dimethylpyrazine, and ethyl acetate in surimi gels with 2.5% YE were 1.5, 21, and 2.1 times higher than those in the control, respectively. Additionally, the sensory results of the spiked aroma models containing WOF compounds, 2,6-dimethylpyrazine, and esters showed that more than 9.4 µg/kg of 2,6-dimethylpyrazine with a baked-potato note and more than 6.1 µg/kg of ethyl acetate and 11.2 µg/kg of butyl acetate with a fruity note could significantly mask WOF. In conclusion, WOF in surimi gels could be masked by YE due to the high concentrations of pyrazines and esters. Practical Application: Yeast extracts could decrease the warmed-over flavor (WOF) due to the high concentrations of pyrazines (baked-potato note) and esters (fruity note). This finding extends the application of yeast extracts in the food industry. On the other hand, this study presents a reasonable solution for the reduction of WOF in surimi products.

Utilizing superheated steam to prepare traditional Chinese twice-cooked pork bellies, exploring its effects on the texture and flavor of fat layers

Fat greatly impacts the overall texture and flavor of pork belly. Twice-cooked pork bellies (TPB), typically boiled and sliced before "back to pot" being stir-fried, is a classic Sichuan cuisine among stir-fried dishes. In this study, the effects of substituting conventional pan-frying (PCV) with superheated steam (SHS) technology on the sensory, texture, microstructure and flavor of the fat layers were investigated. SHS was used as an alternative to boiling (120 °C for 15, 20, 25, and 30 min), and "back to pot" stir-frying was also by SHS. TPB precooked for 25 min (P25) with SHS performed better quality characteristics than PCV, with less collagen fiber disruption and lipid droplet area, resulting in a lower hardness and higher shear force. Besides, the low-oxygen environment of SHS retarded the lipid peroxidation, showing a significantly lower MDA content than PCV. Differently, PCV exhibited more grassy and fatty flavors, while P25 exhibited a unique aroma of fruity and creamy due to its higher UFA/SFA ratios in the pre-cooking stage. Overall, the sensory scores of P25 were comparable to those of PCV (with no significant difference), revealing that SHS is expected to be applied to the industrial production of stir-fried dishes.

Mechanisms of cooking methods on flavor formation of Tibetan pork

To obtain flavor-enriched Tibetan pork products, the impact of oxidation degree on the flavor of Tibetan pork with different cooking methods (microwaving, frying, boiling, and air frying) was evaluated using an E-nose, an E-tongue, GC-MS, and LC-MS. The level of oxidation was lower in M and F and higher in B and AF groups. Hexanal, pentanal, benzaldehyde, 1-octen-3-ol, and 3-hydroxy-2-butanone were identified as significant contributors to cooked samples. The volatile abundance of microwaved, fried, boiled, and air-fried pork was 1.61, 1.22, 1.47, and 1.69 times higher than raw, respectively. Leucine and threonine were detected to be the highest in the AF group, which were 1.30 and 3.60 times greater than RAW, respectively. In summary, oxidation of lipids and proteins caused by cooking treatments was the main source of flavor in cooked Tibetan pork. Air-frying treatment could greatly promote the production of flavor compounds and give unique flavor to Tibetan pork.

Selection and quantification of volatile indicators for quality deterioration of reheated pork based on simultaneously extracting volatiles and reheating precooked pork

This study was to screen and quantify characteristic volatiles tied to the quality deterioration of reheated pork via simultaneously reheating (75 °C, 30 min) and collecting headspace volatiles of precooked pork (100 °C, 10 min; stored: 0 °C, 0-14 d) for GC-MS analysis. The concentrations of hexanal (6.05 ± 0.86-12.05 ± 0.44 mg/kg), (E)-2-octenal (1.54 ± 0.16-3.07 ± 0.08 mg/kg), (E,E)-2,4-heptadienal (1.52 ± 0.44-2.58 ± 0.31 mg/kg) and 8 other selected volatiles in reheated pork increased as the storage time of the precooked counterparts increased. The increase rate of hexanal was 2.9-199 times faster than that of other volatiles based on zero-order reaction fitting (R² = 0.876-0.997). Results from clustering analysis of these volatiles were consistent with their formation pathways tied to lipid autooxidation. This simple approach, reheating and collecting volatiles of precooked meat concurrently, introduces a new possibility for standardizing volatile analysis of precooked meats required being reheated before consumption.

Preparation and Quality Evaluation of Cultured Fat

Cultured meat is rapidly developing as an emerging meat production technology. Adipose tissue plays an essential role in the flavor of meat products. In this study, cultured fat was produced by cultured adipose-derived stem cells (ADSCs) based on collagen in vitro, with a 3D model. The research showed that ADSCs could attach to collagen hydrogels and differentiate into mature adipocytes. Texture analysis demonstrated that the springiness, cohesiveness, and resilience of cultured fat were consistent with porcine subcutaneous fat. Moreover, 28 volatile organic compounds (VOCs) were detected by headspace gas chromatography-ion mobility spectrometry. The relative contents of 17 VOCs in cultured fat were significantly higher than porcine subcutaneous fat and empty collagen hydrogels, and the relative contents of 5 VOCs in cultured fat were not significantly different from porcine subcutaneous fat. These findings assert the promising application of cultured fat in cultured meat production.

Characterization of Key Odor-Active Off-Flavor Compounds in Aged Pasteurized Yogurt by Sensory-Directed Flavor Analysis

The purpose of this study was to determine the key odor-active compounds contributing to the off-flavor of aged pasteurized yogurt (APY) using sensory-directed flavor analysis. Additionally, different extraction methods were compared to determine their effects on the volatile compounds, including dynamic headspace sampling (DHS), solid-phase microextraction, and stir bar sorptive extraction, and DHS was found to be suitable for this study. The results showed that comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry analysis (GC × GC-O-MS) had more advantages in separating and identifying the volatile compounds than the traditional GC-O-MS. A total of 17 odor-active compounds were determined in the fresh pasteurized yogurt and APY samples by DHS coupled with GC × GC-O-MS. The dynamic headspace dilution analysis demonstrated that 2-heptanone and hexanal were the most vital components in APY with the highest flavor dilution factor. Furthermore, the spiking and omission experimental results revealed that the odor-active compounds, such as 2-heptanone, butanoic acid, pentanoic acid, hexanal, and (E)-2-heptenal, were the key odor-active off-flavor contributors in APY. Therefore, these compounds could be used as potential indicators to determine the freshness of pasteurized yogurt.

Evaluation of key aroma compounds and protein secondary structure in the roasted Tan mutton during the traditional charcoal process

The traditional charcoal technique was used to determine the changes in the key aroma compounds of Tan mutton during the roasting process. The results showed that the samples at the different roasting time were distinguished using GC-MS in combination with PLS-DA. A total of 26 volatile compounds were identified, among which 14 compounds, including (E)-2-octenal, 1-heptanol, hexanal, 1-hexanol, heptanal, 1-octen-3-ol, 1-pentanol, (E)-2-nonenal, octanal, 2-undecenal, nonanal, pentanal, 2-pentylfuran and 2-methypyrazine, were confirmed as key aroma compounds through the odor activity values (OAV) and aroma recombination experiments. The OAV and contribution rate of the 14 key aroma compounds were maintained at high levels, and nonanal had the highest OAV (322.34) and contribution rate (27.74%) in the samples after roasting for 10 min. The content of α-helix significantly decreased (P < 0.05), while the β-sheet content significantly increased (P < 0.05) during the roasting process. The content of random coils significantly increased in the samples roasted for 0-8 min (P < 0.05), and then no obvious change was observed. At the same time, β-turn content had no obvious change. Correlation analysis showed that the 14 key aroma compounds were all positively correlated with the content of α-helix and negatively correlated with the contents of β-sheet and random coil, and also positively correlated with the content of β-turn, except hexanal and 2-methypyrazine. The results are helpful to promoting the industrialization of roasted Tan mutton.

Characterization of Warmed-Over Flavor Compounds in Surimi Gel Made from Silver Carp (Hypophthalmichthys molitrix) by Gas Chromatography-Ion Mobility Spectrometry, Aroma Extract Dilution Analysis, Aroma Recombination, and Omission Studies

The warmed-over flavor (WOF) in surimi gels was characterized by gas chromatography-ion mobility spectrometry, aroma extract dilution analysis, aroma recombination, and omission studies. Surimi gels with different WOF levels were prepared by different gelling temperatures, and surimi gels heated at 90, 100, and 121 °C were considered as the samples with light, strong, and medium WOF, respectively. Based on the quantification and odor activity values, 14 aldehydes, 2 ketones, 3 alcohols, 2 benzene-containing compounds, 2 N-containing compounds, 3 S-containing compounds, 3 lactones, undecanoic acid, and 4-methylphenol were recombined to build a spiked model for surimi gels with the strongest WOF, which showed the highest similarity with the original sample. Finally, a triangle test involving omission of the aroma compounds from the spiked model proved that the WOF in surimi gels was attributed to (E,E)-2,4-decadienal, heptanal, octanal, nonanal, decanal, (E)-2-nonenal, (E)-2-octenal, (E)-2-decenal, (E,E)-2,4-heptadienal, 2,3-pentanedione, 2,6-dimethylpyrazine, 2-propylpyridine, benzothiazole, 2-methoxybenzenethiol, and 2-furfurylthiol.

Differences in flavor characteristics of frozen surimi products reheated by microwave, water boiling, steaming, and frying

This study investigated the effects of different reheating methods (microwave, water boiling, steaming, and frying) on the flavor of surimi gels with untreated sample as control. Electronic nose and electronic tongue results showed that microwave could better maintain the original odor and taste characteristics of surimi gels. Additionally, 43 kinds of volatile aroma compounds were detected in surimi gels, including aldehydes, alcohols, ketones, heterocycles, and esters. The aroma fingerprints of surimi gels were similar between water boiling and steaming and between microwave and the control, whereas frying showed the most unique aroma profile possibly related to the highest TBARS values. The total contents of nucleotides, carnosine and lactic acid were significantly higher in fried samples relative to other samples. In conclusion, all the reheating treatments can alter the flavor of samples, but microwave showed better performance in sensory evaluation and maintaining the original flavor of surimi gels.

Changes in volatile profiles of a refrigerated-reheated xylose-cysteine-lecithin reaction model analyzed by GC×GC-MS and E-nose

The changes in the volatile profiles of a xylose-cysteine-lecithin reaction model were investigated by using comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) in combination with headspace solid-phase microextraction (SPME) and electronic nose (E-nose) to evaluate the contribution of refrigerating and reheating treatment to warmed-over flavor (WOF). The volatile compound results and E-nose revealed that the contribution of refrigerating and reheating to the WOF was not consistent. After refrigerating, the level of furfuryl mercaptan increased, while that of 1-octene-3-ol, octanal, nonanal, and 2-decanone decreased, which affected the flavors. An increase in the level of 1-octene-3-ol, 2-pentyl-thiophene, and hexanoic acid and a decrease in the levels of furfural, 2-methyl-3-furanthiol, and 2-methyl-3-pentanethiol occurred during reheating. According to the odor activity value and sensory evaluation, the sulfur-like odor became more intense after refrigerating, while the rancid-like odor grew stronger, but the sulfur-like odor alleviated after reheating. Overall, the reaction between residual substances caused the WOF during refrigeration, also lead to the fatty acid oxidation increased after reheating. The overproduction of fatty acids oxidation products and decreased of volatile product of Maillard reaction leads to the WOF during reheating. PRACTICAL APPLICATION: This study provides theoretical guidance to reduce the off-flavors of meat products.

Characterization of the key aroma compounds in pork broth by sensory-directed flavor analysis

The solvent-assisted flavor evaporation, sensory evaluation, and partial least squares regression analysis were used to screen the relatively better flavor of pork broth among different stewing time (1, 2, 4, 6, and 8 h). A total of 48 volatile compounds were successfully characterized by gas chromatography-mass spectrometry in the pork broth, which stewed for 4 h. The dominant volatiles were confirmed by aroma extract dilution analysis. Twenty-seven odorants with flavor dilution factors between 2 and 1,024 were identified. Among them, odor activity values of 19 components were greater than or equal to 1. An aroma recombination test was performed, and a similar flavor (93.04 %) was simulated. Omission test further confirmed that 4-hydroxy-2,5-dimethyl-3(2H)-furanone, hexanal, 1-octen-3-ol, (E)-2-octenal, (E)-2-decenal, (E)-2-undecanal, (E, E)-2,4-decadienal, nonanoic acid, decanoic acid, 2-heptanone, 3-hydroxy-2-butanone, δ-decanolactone, and 2-acetylpyrrole were the key odorants of the aroma profile of pork broth. PRACTICAL APPLICATION: Pork broth is popular in China, but lacks the study of its key aroma compounds, which restricts its industrial production. This study researched the optimum stewing time of pork broth and analyzed its key aroma compounds. Finally, the flavor profile can be obtained and understood. This study could provide a reference and further promote research on pork flavor.

Comprehensive SPME-GC-MS Analysis of VOC Profiles Obtained Following High-Temperature Heating of Pork Back Fat with Varying Boar Taint Intensities

Boar taint detection is a major concern for the pork industry. Currently, this taint is mainly detected through a sensory evaluation. However, little is known about the entire volatile organic compounds (VOCs) profile perceived by the assessor. Additionally, many research groups are working on the development of new rapid and reliable detection methods, which include the VOCs sensor-based methods. The latter are susceptible to sensor poisoning by interfering molecules produced during high-temperature heating of fat. Analyzing the VOC profiles obtained by solid phase microextraction gas chromatography–mass spectrometry (SPME-GC-MS) after incubation at 150 and 180 °C helps in the comprehension of the environment in which boar taint is perceived. Many similarities were observed between these temperatures; both profiles were rich in carboxylic acids and aldehydes. Through a principal component analysis (PCA) and analyses of variance (ANOVAs), differences were highlighted. Aldehydes such as (E,E)-nona-2,4-dienal exhibited higher concentrations at 150 °C, while heating at 180 °C resulted in significantly higher concentrations in fatty acids, several amide derivatives, and squalene. These differences stress the need for standardized parameters for sensory evaluation. Lastly, skatole and androstenone, the main compounds involved in boar taint, were perceived in the headspace at these temperatures but remained low (below 1 ppm). Higher temperature should be investigated to increase headspace concentrations provided that rigorous analyses of total VOC profiles are performed.

Effects of Shiitake (Lentinus edodes P.) Mushroom Powder and Sodium Tripolyphosphate on Texture and Flavor of Pork Patties

Increasing consumer desire for functional food ingredients, including such PRODUCTS as shiitake mushroom (Lentinus edodes P.) powder (SM), demands that the sensory impact of such ingredients be tested in an appropriate food system. Pork patties are a common food in many Asian countries. Pork patties in this study were prepared with and without SM, an ingredient that is gaining popularity around the world. A lexicon for describing the texture and flavor of cooked pork patties, with and without 0.5% sodium tripolyphosphate (STP), a typical additive to meat, and with varying amounts of SM (0% to 6%) was developed by a highly trained panel to compare sensory properties for each type of patty. The attributes evaluated were juiciness, toughness, rubberiness, mealiness, pork identity (pork ID), meatiness, mushroom, onion, garlic, black pepper, heat/burn, soapy, chemical, animal hair, fatty, salty, sour, bitter, slick, and astringent. An addition of 0.5% STP produced more intense ratings for soapy, salty, sour, and astringent attributes. Without STP, patties containing shiitake mushroom powder had a more mealy consistency but more pork ID than they did with STP.