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Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2020 Jun 20;58(2):651–659. doi: 10.1007/s13197-020-04579-z

Multivariate analysis approach for assessing coated dry-cured ham flavor quality during long-term storage

Yanan Shi 1, Xiang Li 2, Aixiang Huang 1,✉
PMCID: PMC7847921  PMID: 33568859

Abstract

This study aimed to investigate the effect of coatings on the quality of ripened dry-cured hams during long-term storage, especially the profile of volatile compounds. The coatings were made up of 33% palm oil, 16.5% water, 39.7% cassava starch, 6.8% corn starch, 1.6% mono- and diglycerides of fatty acids, 0.6% tert-butylhydroquinone (TBHQ), and 1.8% sodium carbonate. The results showed that the moisture content of the coated ham (48.93–49.59%) was higher than that of the noncoated ham (44.37%). The average peroxide value (POV) and b* value were lower in the coated hams than in the noncoated hams (5.52 and 8.99 meq/kg, respectively), and the sensory attributes of the coated hams had better overall acceptability scores. The changes in the contents of 39 volatile flavor compounds were evaluated through a multivariate statistical analysis, revealing that 20 identified compounds could be related to the decrease in fat pungent aroma, and most belonged to the long-chain benzene and carboxylic acid family. Meanwhile, 2-nonanone, nonanal, amyl alcohol, and 2-heptanone indicated that they could be used as markers to distinguish between the coated and noncoated groups.

Electronic supplementary material

The online version of this article (10.1007/s13197-020-04579-z) contains supplementary material, which is available to authorized users.

Keywords: Dry-cured ham, Food grade coating, Volatile compounds, Flavor defects, Surface defect

Introduction

Dry-cured hams are a popular cured meat product, with long storage process, typical flavor characteristics, and excellent consumer acceptance. Yunnan province of China has a long-standing history of dry-cured ham production, where many types of dry-cured hams have been commercially produced and are available on the market with a high commercial value. After mixing salt on the green leg and the production process (post-salting for equalization, ripening–drying), hams are typically stored in the aging house to develop intense and desirable flavor characteristics. Occasionally delayed sales force hams to be stored for 1.5 years, which exceeds the Chinese National Standard of 10 months (Qiao et al. 2006). Thus, three issues of dry-cured hams during storage have become research hotspots. First, a high drying rate can lead to a higher risk of surface hardening and cracking. Second, mite infestations occur because of high protein content, fat composition, and water activity of ham. Third, hams aged more than 18 months have more intense flavor compared with shorter-aged hams. They also have a stronger fat pungent aroma in the semimembranosus muscles. The aggravation of bad odor due to the excessive oxidation of fat on the surface of hams considerably decreases the economic value of hams during storage (Morales et al. 2008; Narváez-Rivas et al. 2013).

Several preventive measures have been proposed to overcome these problems. Previous studies showed that applying a layer of lard or fat or vegetable oils on the lean area of hams was an effective practice to avoid excessive drying or dehydration during long-term aging (Abbar et al. 2018; Campbell et al. 2018; Rajendran and Parveen 2005; Zhao et al. 2016) and especially for controlling arthropod pest and mite infestations of dry-cured hams (Campbell et al. 2018). The effect of packaging on ham quality has also been analyzed (Gonzalez et al. 2009), vacuum packaging of hams can reduce the fat rancidity and increase the brightness of biceps femoris (p < 0.1) until 8 months of storage (Molinero and Arnau 2008). The relative humidity of the aging house often affects the pH, composition, and appearance of the surface of dry-cured hams (Arnau et al. 2003; Hendrix et al. 2018). Also dry-cured ham has been largely studied for its physico-chemical and sensory quality depending on the application of compound xanthan gum, carrageenan material, and other food-grade compounds (e.g., short-chain alcohols, sorbic salts, propionic salts, and butylated phenol preservatives) as coatings can effectively inhibit the oxidation of ham and significantly promote the sensory (Abbar et al. 2016). These studies focus on investigated the effects of coating treatment, packaging, storage environment on physical and sensory properties of dry-cured hams. However, little research has been dedicated to this diversification on volatile flavor composition. In addition, the enormous data acquired from GC–MS requires the use of a multivariate data analysis to detect the similarity and discrepancy between the observations in volatile compounds, and understand characteristic flavor compounds.

In this work, the development of a composite coating materials made from cassava starch and corn starch incorporating antioxidant and emulsifier molecules was studied. Firstly, the effects of coating treatment on volatile flavor compounds of whole aged dry-cured hams during storage period were evaluated, as well as moisture retention and sensory characteristics. Thereafter, the most effective parameters of coating material was studied, to ensure the stability of flavor compounds during long-term storage. The results propose a preservation method that was affordable for ham producers to control the final product quality, increase product shelf life during shelf life and efficiency of production.

Materials and methods

Sampling, coating materials, and storage of whole dry-cured hams

In this study, the green hams from crossbreed (Duroc × local Dahewu variety) with average weight of 10 kg, were taken from Yunnan Dongheng Ham Co. Ltd. (Yunnan, China), and 18 hams were processed in the company according to the following technology: The green hams were aged for 18–36 h in a cold room to keep the central temperature at 3–4 °C, then dry salted using sea salt (55 g/kg green ham) maintained in a cold room at 2–3 °C with 85–90% relative humidity (RH) for 24 days, followed by a drying balance stage that the salted legs were hung in a balance room at 7–8 °C, 70–75% relative humidity for 60 days. After that the drying hams were kept in 22–24 °C, RH 65% for the ripening process until to 10 months. For coating experiments, these hams were divided into three groups, six hams in each group: (1) coating treatment 1 (coated with 33% palm oil, 16.5% water, 39.7% cassava starch, 6.8% corn starch, 1.6% mono-and diglycerides of fatty acids, 0.6% TBHQ, and 1.8% sodium carbonate); (2) coating treatment 2 (coated with 40.6% palm oil, 10% water, 43.7% cassava starch, 3.4% plant ash, 0.6% TBHQ, and 1.7% emulsifier); and (3) non-treated (NT), control. These amounts of coating material in treatment 1 and 2 was determined by a response surface design (Keenan et al. 2014), for additional testing (viscosity, rheological, antioxidant and barrier properties analysis). The coatings were evenly daubed on the ham surface, and the coating thickness was 0.5 cm. The samples were stored at 22–24 °C, with relative humidity between 65 and 70%. Hams were always hung with the lean surfaces facing each other 5 cm apart (Fig. 1). The sensory, physicochemical, and volatile compounds of 18 hams were analyzed after 9 months of storage.

Fig. 1.

Fig. 1

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Different coating treatments for ripened dry-cured ham samples in the aging house during the 9-month storage; uncoated ham products were used as negative controls

Sensory evaluation

The sensory analysis was conducted by a trained panel (16 experts with 4–12 years of sensory evaluation experience) with a good command of sensory methodology and familiarity with the sensory quality. Between two tastings, the assessors drank hot tea to neutralize the taste. The samples were cut into 10-mm-thick slices (including semimembranosus and biceps femoris muscles, 1-cm cover fat) and steamed in a cooker for 20 min. Each attribute was scored on 10-cm nonstructured lines with anchor points at each end (0 = absent; 10 = very strong). The sensory quality was characterized on the basis of 10 sensory attributes, grouped in redness (meat color), whiteness (fat color), color homogeneity, brightness; flavor intensity (fat pungent aroma, musty aroma, ham flavor, “other” flavor); sweet aftertaste, saltiness, and overall quality.

Volatile compound analysis

An SPME fiber coated with carboxen-poly (75-lm thickness, Supelco Co., PA, USA) was inserted through the septum and exposed to the headspace of the SPME vial. The biceps femoris and semimembranosus muscle slices from each ham unit ground and homogenized together, weighing 5.0 g, from dry-cured hams were pretreated with a saturated water bath at 50 °C for 40 min during the extraction procedure. After extraction, the SPME fiber was immediately injected into a 6890 N gas chromatograph coupled to a 5975i mass-selective detector (Agilent Technologies, CA, USA). The volatiles were separated using a capillary column (DB-5 ms 30 m × 0.25 mm, film thickness 0.25 μm) with helium as a carrier gas at the 1.0 mL/min flow rate. The sample was desorbed in the injection port of the GC at 250 °C with a split ratio of 1:30. The temperature-programming sequence was as follows: an initial temperature of 40 °C for 5 min, then increased to 90 °C at a rate of 5 °C/min and then to 250 °C at a rate of 12 °C/min, and finally held for 7 min. The mass spectra were obtained at 70 eV at a scan rate of 1 scan/s over the m/z range of 50–450 amu. The compounds were identified by comparing the mass spectral data of the samples with those of the NISTDEMO library. The mass spectra obtained were investigated carefully, and only molecules with a matching probability of > 80% were considered.

Physicochemical determinations

The samples in sextuplicate were used to determine the moisture content, levels of sodium chloride (NaCl) and sodium nitrite (NaNO2), water activity, and peroxide value. The mixed samples of biceps femoris and semimembranosus muscles were used for determining the peroxide value. The moisture content was evaluated following the Chinese National Standard GB/T 9695.15-2008. The content of NaCl was determined by potentiometric titration with AgNO3 using an autotitrator. The water activity (aw) was measured at 25 ± 0.3 °C with a Novasina AW SPRINT-TH 500 instrument (Axair Ltd., Pfäffikon, Switzerland), according to the manufacturer’s protocols. The NaNO2 concentration was evaluated following the Chinese National Standard GB5009.33-85. The peroxide value (POV) was evaluated following the Chinese National Standard GB/T 5009.37. A portable spectrophotometer (Konica Minolta CM-700d, Osaka, Japan) was used to estimate the meat color: lightness (L*); redness (a*); and yellowness (b*). Each sample was cut into slices (2.5 cm thick), and the readings were immediately taken at five different locations, avoiding regions with excess fat to achieve representative measurements of the lean color. Before each series of measurements, the instrument was adjusted using a white ceramic tile.

Statistical analysis

Multivariate statistical techniques have been widely used for assessing the quality of dry-cured hams (Abdi 2008; Sampaio et al. 2017). These tools help simplify and organize large datasets of volatile flavor compounds to explain the observed relations among different treatments. Principal component analysis (PCA) and unsupervised and supervised partial least-squares discriminant analysis (PLS-DA) were performed on 18 samples with SIMCA 13.0 (Umetrics, Umeá, Sweden). The discriminating metabolites were obtained from the PLS-DA model, where the metabolites with variable importance in the projection values higher than 1 were selected (Heude et al. 2016; Jurado et al. 2007; Wang et al. 2016). In the hierarchical clustering heatmap analysis, the data were imported into the software (Heatmap Illustrator, version. 1.0). The statistical analysis of the results of physicochemical properties and sensory evaluation was performed using a one-way, p value less than 0.05 was considered statistically significant using the SPSS package (SPSS 19.0, IL, USA).

Results and discussion

Sensory, physical, and chemical parameters of coated dry-cured hams

Regarding the effects of the coating procedure after 9 months of storage and consumption period, the mean intensity ratings for the 10 sensory attributes are shown in Table 1. Fat pungent aroma is a complex parameter, which is more frequent in long-aged hams due to the oxidation on the surface of unsaturated fat. The control had higher scores on the sensory evaluation of fat pungency (p < 0.05). No detectable difference was found between the treated hams and the control in terms of fat color (white), meat color (red), saltiness, and other aroma intensities (p > 0.05). The sensory attributes, such as musty flavor, were not detected in all the three groups of dry-cured ham samples. The samples were coated and stored for 9 months, and hence had high overall acceptability with color homogeneity, which was characterized by rose-red color and bright white fat. Campbell et al. (2018) evaluated that the effectiveness of polyester blend nets treated with food-grade coatings (xanthan gum, propylene glycol, carrageenan, propylene glycol alginate and propylene glycol) on dry-cured ham, without impacting sensory properties and texture, the results are confirmatory of the texture evaluation results of the current study. Vacuum packaging during resting caused an increase in white film and feedstuff flavor, as well as a decrease in aged flavor, hardness, fibrousness and overall liking (Molinero and Arnau 2008). The main conclusion is that the coating treatment of aged dry-cured ham product, does not markedly modify its texture attributes and overall sensory parameters, but could be decrease in the fat pungent aroma, because the excessive oxidation of fat on the surface of hams was prevented.

Table 1.

Sensory attributes (mean ± standard error; n = 6) of dry-cured hams with three coating treatments

Intensity of studied attributes [0–10 c.u.] Coating treatment 1  Coating treatment 2 Noncoated control p-value
Fat color 7.98 ± 0.8ab 8.6 ± 0.1a 8.6 ± 0.3a 0.160
Meat color 8.35 ± 1.5a 8.66 ± 1.9a 8.04 ± 1.3ab 0.660
Color homogeneity, brightness 7.9 ± 0.78a 7.6 ± 1.38a 6.77 ± 0.67b 0.039
Fat pungent flavors 4.1 ± 1.02a 3.8 ± 1.4a 7.89 ± 0.59bc 0.027
Musty aroma 0 0 0 –
Ham flavor 8.3 ± 0.66b 8.9 ± 1.0a 8.1 ± 0.87b 0.309
“Other” flavor 1.61 ± 0.3b 1.56 ± 0.59b 1.5 ± 0.44b 0.060
Sweet aftertaste 8.6 ± 1.3a 8.5 ± 1.56a 6.0 ± 1.1a 1.157
Saltiness 6.6 ± 1.02a 6.8 ± 1.9a 7.6 ± 1.04a 1.198
Overall quality 8.8 ± 0.6a 8.3 ± 1.1a 7.7 ± 1.1b 0.103
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a,b,cWithin a row, means with different letters in the same row are significantly different (p < 0.05)

Coating hams with lard is a common practice in the western-style ham, which may not be permeable to moisture and thus extend the drying and aging time. As expected, coating with preservatives leads to significant changes in the moisture content, with the higher moisture content (48.93–49.59%) in the coated groups than in the control group (44.37%) (Table 2). The ham has less than 45% moisture content. The coated hams had the highest value in the sensory analysis, indicating the sensory attribute of hard texture during long storage, which suggested that many consumers did not like too hard or dry texture of dry-cured hams. Similarly, Hendrix et al. (2018) evaluated the effect of applying lard on the ham surface during storage. The moisture content between 48 and 53% to prevent the ham from drying and hardening during storage and consumption was in agreement with the results obtained. However, Sánchez-Molinero and Arnau (2014) reported that the application of a small amount of oil drip from lard increased the moisture loss in the semimembranosus muscle but did not affect the moisture content of the biceps femoris muscle. This was probably due to the reduction of crustiness, which increased effective water diffusivity (Gou et al. 2004). Different from this study, the protective effect of coatings might be related to the nature of the daub material and the application period. In this study, 10-month-old hams were selected. The coating treatment during shelf life could decrease the b* value in the noncoated ham (15.04) compared with the coated hams (8.99–10.07) (p < 0.05). The decrease in the b* value could be due to oxygen consumption and a decrease in the oxymyoglobin content that controls the yellowing of fat under the physical sealing of coatings, without impacting the a* value. The oxidation of lipids is a major concern in cured meat. Some oxidation was observed during the storage period, which was caused by the low superficial oxygen concentration in the coated dry-cured hams. The POV value of the noncoated samples (9.46 mEq/kg) was higher than that of the coated ones (5.52 meq/kg) throughout the storage. These results were in accordance with the determination of the intensity of fat pungent aroma.

Table 2.

Physicochemical parameters and instrumental color (mean ± standard error; n = 6) of dry-cured hams with three coating treatments

Coating treatment 1 Coating treatment 2 Noncoated control p-value
Moisture (g/100 g) 49.59 ± 1.56a 48.93 ± 1.12a 44.37 ± 0.86c 0.022
NaCl (%) 7.8 ± 0.46a 8.2 ± 1.49a 9.00 ± 0.65a 0.176
POV (meq/kg) 5.52 ± 0.02a 6.30 ± 0.02a 9.46 ± 0.03c 0.046
NaNO2 (ppm) 0.36 ± 0.15b 0.37 ± 0.13b 0.47 ± 0.21a 0.111
aw 0.82 ± 0.01a 0.82 ± 0.01ab 0.81 ± 0.01c 0.102
L* 33.20 ± 1.50a 32.97 ± 1.88a 31.02 ± 0.61a 0.507
a* 8.15 ± 0.59c 8.36 ± 0.50a 8.15 ± 0.95b 0.332
b* 8.99 ± 0.59a 10.07 ± 0.76ab 15.04 ± 0.30b 0.021
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a,b,cWithin a row, means with different letters in the same row are significantly different (p < 0.05)

The L* value was 33.20–32.97 in the coated hams, which was higher than that in the noncoated dry-cured hams (31.02) (p < 0.05). Estévez et al. (2003) reported that the moisture loss resulted in a reduction in L* values, which depended on the water content on the surface (thin aqueous layer). The coating treatment in the hams aged 10 months did not affect the salt content, nitrite concentration, water activity, and redness value. The aw value did not differ among the three groups of dry-cured hams and was between 0.81 and 0.82. The salt affected both the quality and the safety of aged hams. In this study, the salt and NaNO2 content showed no significant difference in the three groups of dry-cured hams, which was in accordance with previous reports on the salt and NaNO2 content in other types of dry-cured ham products (Hinrichsen and Pedersen 1995; Huang et al. 2011; Petričević et al. 2018).

Difference in volatile flavor compounds due to the coating preservative

To obtain the metabolite information leading to the significant difference, partial least square (PLS-DA) regression models were built based on the GC–MS profiles of the three groups of samples. The model showed high predictive ability (R2X = 0.869, R2Y = 0.871, Q2 = 0.541) for estimating the different substances in the three groups. The PLS-DA pattern could amplify variations to achieve further clustering (Zheng et al. 2018). Therefore, the PLS-DA pattern was applied to see the clustering and classification of the 18 samples collected from dry-cured hams. The PCA-loading vectors also revealed the contribution of each flavor substance (Fig. 2). Meanwhile, 2-nonanone, nonanal, amyl alcohol, and 2-heptanone were distant from the point (0, 0) on the PC1 dimension, indicating that they could be used as markers to distinguish between the coated and noncoated groups. Coating treatment dry-cured hams showed higher content of 2-nonanone, amyl alcohol, while nonanal, 2-heptanone are the characteristics compounds of non-treated dry-cured hams (Additional Fig. 1). Nonanal was typical for the control hams (Dahe black pig ham) which is in arrangement with other authors (Shi et al. 2019).

Fig. 2.

Fig. 2

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PCA-loading map of the different coating treatments with the changes in the volatile compounds of dry-cured hams

The statistical analysis showed significant differences (p < 0.05) in the total volatile content among groups. From an analytical point of view, thirty-nine compounds were significantly influenced by the coating material. The hierarchical clustering heat-map analysis was used to observe the relative content of volatile flavor compounds in samples based on the change in color, which meant the deeper the color, the larger the content. The moisture content and the oxidation extent were the physicochemical parameters with the most pronounced effect on coated dry-cured hams. The results combined with GC–MS and heatmap showed that the compound coatings could decrease the relative contents (p < 0.05) of 20 volatile compounds, including 5-ethyldecane, hexanoic acid, tetradecane, nonanal (rancid, fatty), undecane, 1,3-dimethyl-benzene, 2-methyl-propanoic acid, carbonic acid, ethylbenzene, 2-ethyl-1-decene, o-xylene, octanol (fatty, strong acid), benzaldehyde (burned meat, cooked meat), dodecane, octanal (stew-like, boiled meat-like, rancid, grass, fruity), 2-ethyl-1-hexanol (fat rancid flavor, and fat pungent flavor), benzeneacetaldehyde (floral), methyl-benzene (strong plastic, glue), p-xylene, and methanethiol (sulfur). About the descriptors and thresholds for compounds have been reported (Carrapiso et al. 2002; Garcia-Gonzalez et al. 2008). This could be related to the decrease in the compounds accounting for fat pungent aroma, which could be divided into branched-chain benzene and carboxylic acids, the results are shown in Fig. 3. Similar results were obtained in this study, lower levels of compounds, such as nonanal, benzaldehyde, octanal, methyl-benzene, were found in coated dry-cured hams, which could have been adsorbed into the coating material, because at least partly, of their lipophylic nature which favors their retention by the fat phase of hams (Willige et al. 2000). Then, Dry-cured with coating preservative do not favor bacterial growth, benzaldehyde, styrene could also come from mould metabolism (Serra et al. 2007), so the production of metabolic volatile compounds by microorganisms is somehow restricted, the reduction the relative contents (p < 0.05) of branched-chain benzene, explain the effect of coating treatment of ham surface. Ana et al. (2009) observed that another way to increase product shelf life of Serrano ham, packaged with a multilayer polymeric bag and high pressure treatment, some linear and branched chain ketones and some sulphur compounds, pyrazines and furans decreased with treatment.

Fig. 3.

Fig. 3

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Each column shows a sample, and each row represents a metabolite. The color represents the relative expression of the metabolite in the sample. Red represents the higher expression of the metabolite in the sample, while green represents lower expression. The number label under the upper left color bar represents the changing trend of the specific expression (color figure online)

The long-chain alkanes probably did not have a substantial impact on flavor because they had relatively high odor threshold values (Hoyland and Taylor 1991). The five benzene derivatives (methyl-benzene, p-xylene, benzeneacetaldehyde, 1, 3-dimethyl-benzene, and o-xylene) and 2-ethyl-1-decene were absent in the coated group; the fat pungent aroma might be attributed to benzene type. The odor thresholds of the volatile compounds were described earlier, and their sensory characterization was performed by dilution analysis (Hau and Connell 1998). These substances have their own unique flavor characteristics when they exist alone, but their volatile sensory characteristics can change with the concentration and possible synergy with other compounds from the matrix. The consumer acceptability scores were reported to be lower for hams characterized by branched benzenes, such as benzeneacetaldehyde, benzaldehyde, and methanethiol (Dirinck and Opstaele 1998; Ruiz et al. 1999; Sabio et al. 1998). Benzaldehyde may originate from phenylalanine catabolism (Mcsweeney and Sousa 2000). The floral/rose-like aromas of benzene acetaldehyde are associated with the “cured” parameters used to describe the American dry-cured ham during the descriptive analysis (Pham et al. 2008).

An increase in 2,3,5-trimethyl pyrazine, 2,6-dimethyl-pyrazine, 2-hydroxy-propanoic acid-ethyl ester, 2-nonanone (floral, fruity, blue cheese), 2-octanone (fruity, green, floral, fresh), 8-nonen-2-one, 2-ethyl-1-decene, octane (sweet), 3-hydroxy-2-butanone, l-limonene (flower, solvent-like, fruity, citrus), dimethyl-trisulfide, undecane, dimethyl-disulfide (cauliflower, rotten vegetables, spoiled ham, burned), γ-hexalactone, methanethiol, octanol, 3-hydroxy-2-butanone, and methyl-oxirane was found in the coated hams (p < 0.05). Coating treatment can increase the strength of branched chain ketones, pyrazines, alkanes and terpenes in dry-cured ham semimembrane and biceps femoris. Branched-chain ketones could be derived from proteolysis (Motilva et al. 1992). The hams aged in an air atmosphere had a lower proteolysis index compared with those aged in coating materials with a reduced oxygen content.

Determine the best formula of coating material

Principal component analysis (PCA) was conducted on the normalized GC–MS/MS data, as one of the descriptive multivariate analyses, performed to determine the relationship between the variables and the observation points with a graphical presentation. Figure 4 showed that 30.5% of the total variables was explained by PC1 (17.9%) and PC2 (12.6%). In the score plot, a clear separation between the samples was observed; moving from right to left along PC1, the result showed that CT1- and CT2-treated hams were differentiated from the noncoated control. The control hams were located on the right-most area of PC1, indicating that the use of coatings had an effect on the volatile flavor components of hams at this stage. Coating treatment 2 of hams, showed obvious separation on PC1 and PC2 among six ham samples, this results reveal that CT2 failed to control the stability of ham flavor compounds compared with CT1, resulting in a difference in the relative contents and class of flavor compounds. CT1 treatment is most appropriate for whole hams on the basis of “maintain flavor stability” during the long storage. The coatings were made up of 33% palm oil, 16.5% water, 39.7% cassava starch, 6.8% corn starch.

Fig. 4.

Fig. 4

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Sample score plot of the principal component analysis (PCA) of the volatile compounds of hams with coating treatment 1, coating treatment 2, and noncoated control during the 9-month storage

Primarily ingredients (e.g., cassava starch and corn starch) of CT1 were agricultural by-products. Starch has good film-forming, high barrier properties and low cost (Tavares et al. 2019; Travalini et al. 2019). Cassava and corns starch rich amylose content and presented hydrophobic and biodegradable properties, helps to retain water, and can be applied as food field (Orozco-Parra et al. 2020). The remaining ingredients including Mono- and diglycerides, TBHQ and sodium carbonate. Biodegradable coatings has been one the most important trends in meat science, allowing the increase of shelf-life times for hams by incorporating antioxidant molecules into their polymeric structure. Mono- and diglycerides are emulsifiers containing both the hydrophilic and hydrophobic functional groups in the same molecule, used to modify the viscosity of the coating materials (Loi et al. 2019). Jain and Sharma (2010) compared the efficiency of three synthetic antioxidants (TBHQ, pyrogallol, and propyl gallate) in biodiesels and they concluded that antioxidants significantly stability among them. The use of these specific coatings affordable for ham producers with efficiency of production, the coating material can be firmly attached to the surface of the ham, and will not fall off during the 9-month storage period.

Conclusion

This study revealed differences in 39 volatile flavor compounds due to the coating treatment of aged whole dry-cured hams. Of these, 20 identified compounds could be related to the decrease in the fat pungent aroma, most belonged to the long-chain benzene and carboxylic acid family. Coating treatment is useful for moisture retention of hams, effectively solving the problems of hardness, and has positive effects on during the 9-month storage. CT1 was most appropriate on the basis of “maintain flavor stability”. This process is affordable for ham producers to extend the shelf life and efficiency of production.

Electronic supplementary material

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Supplementary material 2 (TIFF 1388 kb) (1.4MB, tif)
Supplementary material 3 (TIFF 1320 kb) (1.3MB, tif)
Supplementary material 4 (XLSX 150 kb) (150.8KB, xlsx)

Acknowledgments

The authors thank the Yun-ling industrial technology leading talent (Grant No. 2014-1782); The research and development workstation of Yunnan provincial experts [Grant No. Yunrenshefa (2017) No. 38] and the 12th student science and technology innovation and entrepreneurship action fund of Yunnan Agricultural University (Grant No. 2019ZKX097) for financial support. They also thank Yang Liu and Yi Zhao for their kind help in the processing and quality control of hams.

Compliance with ethical standards

Conflict of interest

The authors declare they have no Conflict of interest.

Footnotes

Publisher's Note

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Contributor Information

Xiang Li, Email: qjfylx@126.com.

Aixiang Huang, Email: aixianghuang@126.com.

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