Enhancing saltiness perception in bone broth: the additive effect of oil and optimization of sodium-reduction formula for consumer acceptability.

BACKGROUND: Excessive NaCl intake in liquid and semi-solid food (e.g. soup, hot pot base, sauce) poses a high risk to human health, and reducing NaCl intake is a major concern for global health. RESULTS: Using the generalized Labeled Magnitude Scale (gLMS) method, the study verified the possibility of sodium reduction through oil addition. The compromised acceptance threshold (CAT) and hedonic rejection threshold (HRT) were determined. The gLMS results showed that the saltiness intensity of samples containing 0.36% NaCl and 2.29% sunflower seed oil was significantly higher than that of samples containing only 0.36% NaCl (P < 0.05). CAT and HRT results indicated that by adding 3.59% sunflower oil, the NaCl content could be reduced to a minimum of 0.14% without causing sensory rejection in bone broth samples. The quantitative descriptive analysis method was used to determine the effects of NaCl and oil concentrations on the sensory attributes of bone broth samples. Furthermore, it was used to analyze the consumer acceptability drivers in combination with the hedonic scale to optimize the formulation of reduced-salt bone broth products. Notably, sample E (0.36% NaCl, 2.29% fat) not only had a significant salt reduction effect with a 20% decrease in NaCl, but also had improved overall acceptability. CONCLUSION: This study provides theoretical guidance for designing salt-reduction cuisine within the catering and food industries, including bone broth and hot pot bases. © 2024 Society of Chemical Industry.

The relationship between alkylamide compound content and pungency intensity of Zanthoxylum bungeanum based on sensory evaluation and ultra-performance liquid chromatography-mass spectrometry/ mass spectrometry (UPLC-MS/MS) analysis.

BACKGROUND: Zanthoxylum bungeanum originating in different places varies in alkylamide content and pungency intensity. RESULTS: The pungency intensity of 19 Zanthoxylum bungeanum samples was first determined with Scoville pungency units (SPUs). The SPUs were found to range from 3.80E + 04 to 5.40E + 05. The chemical compositions and contents were measured next, using the ultra-performance liquid chromatography-mass spectrometry/ mass spectrometry (UPLC-MS/MS) method. The total alkylamide content ranged from 9.83 ± 0.15 to 89.98 ± 1.35 g kg-1 . Hydroxy-ϵ-sanshool, hydroxy-α-sanshool, hydroxy-ß-sanshool, hydroxy-γ-sanshool, bungeanool, and isobungeanool were found to be the key pungent compounds, ranging in proportion from 92.65% to 97.69%. The relationship between alkymide compound content and pungency intensity was also analyzed by ridge regression, and it was found that the ß values of independent variables were stable when k was more than 0.6. The regression coefficients of hydroxy-ϵ-sanshool, hydroxy-α-sanshool, hydroxy-ß-sanshool, hydroxy-γ-sanshool, bungeanool, isobungeanool, and other alkylamides were 0.105, 0.177, 0.386, -0.166, -0.006, 0.005, and -0.018, respectively. CONCLUSION: Hydroxy- sanshool compounds were important in determinant the pungency intensity of Z. bungeanum. Knowledge of the relationship between alkymide compound content and pungency intensity will assist in the creation of new methods to determine pungency intensity and provide a scientific basis for flavor design, development of pungent food products, and consumer choice evaluations. © 2018 Society of Chemical Industry.

Pungency Evaluation of Hydroxyl-Sanshool Compounds After Dissolution in Taste Carriers Per Time-Related Characteristics.

This study was conducted to investigate the sensory characteristics and temporal migration of hydroxyl-sanshool compounds at slight and moderate concentrations after dissolution in ethanol-water, saccharose, NaCl, and MSG via 2-AFC, time intensity (TI) and temporal dominance of sensations (TDS) methods. The pungency detection threshold (DT) was suppressed in saccharose while NaCl and MSG solutions showed no effect on pungency DT. The area under the curve (AUC) of pungency increased in NaCl and MSG solutions and decreased significantly in saccharose solution. Imax (maximal intensity) also increased in NaCl and MSG at low concentrations of hydroxyl-sanshool compounds. The temporally dominant sensations and migration of said sensations across the oral cavity differed among different carriers. Low levels of pungency compounds were characterized by tingling first in the tongue tip and ending in the lips, while moderate levels of the compound produced tingling, astringency, vibrating, and numbing from the tongue tip to the bilateral sides of the tongue, lips, palate, cheek mucosa, and surface of the tongue over time. There were significant differences in the maximum rate, peak time, and duration of any dominant sensation, as well as in the duration of sensation in the lips, tongue tip, and bilateral sides of the tongue. This study provides a dynamic profile of consuming pungent food, which provides a reference not only for the design of new food products with desirable pungency, but also as a scientific basis for the application of pungent compounds within the food and catering industry.

Aroma Characteristics of Green Huajiao in Sichuan and Chongqing Area Using Sensory Analysis Combined with GC-MS.

Green huajiao has a unique flavor and is widely used in cooking as an edible spice. In this study, the intensity of overall aroma and aroma attributes of seven green huajiao samples from the Sichuan and Chongqing regions were evaluated using a dynamic dilution olfactometer and ranking descriptive analysis (RDA) technology. The volatile compounds and major aroma components were determined by GC-MS in combination with odor activity value (OAV) analysis. The partial least squares regression (PLSR) model was further used to identify the key aromas contributing to the aroma sensory attributes. Seven green huajiao samples were categorized into three groups: (1) huajiao samples from Liangshan have a strong intensity of pungent, floral and herbal aromas and a medium-high intensity of sweet aroma, and the key contributing aroma compounds were α-pinene, sabinene, ß-pinene, myrcene, ocimene and linalool; (2) huajiao samples from Panzhihua and Hongya have a strong intensity of citrusy, lemony and minty aromas, and the key contributing aroma compound was linalool; and (3) the huajiao sample from the Chongqing region was categorized into a separate group and was characterized by a medium-high intensity of green, minty and sweet aromas, and the main aroma compounds are ocimene, citronellal and α-terpineol. These results provide useful basic data for evaluating the aroma quality and analyzing the key aroma characteristics of green huajiao in the Sichuan and Chongqing regions.

Rapid determination of geographical authenticity and pungency intensity of the red Sichuan pepper (Zanthoxylum bungeanum) using differential pulse voltammetry and machine learning algorithms.

The development of an analytical method for assessing pungency intensity and determining geographical origins is crucial for evaluating the quality of visually similar Zanthoxylum bungeanum pericarp (PZB). This study analyzed 210 PZB samples from 14 origins across China, focusing on origin adulteration identification and pungency intensity using a combination of differential pulse voltammetry (DPV) and machine learning algorithms. The artificial neural network (ANN) and K-nearest neighbor (KNN) algorithms provided the highest accuracy in origin identification (100 %) and adulteration detection (97.9 %) respectively. Moreover, the ANN excelled in predicting pungency intensity (R2 = 0.918). Assessment via feature importance analysis of DPV features revealed that segments of polyphenols (0.34-0.52 V and 1.0-1.2 V) and alkylamides (1.0-1.2 V) contributed significantly to the PZB pungency intensity. These findings highlight the potential of DPV as a reliable method for assessing the quality of PZB, and offer a promising solution for ensuring the geographical authenticity of this important crop.

An assessment of the sensory drivers influencing consumer preference in infant formula, assessed via sensory evaluation and GC-O-MS.

Consumer partiality for food products is related to purchase and consumption behavior, and are influenced by sensory preferences. The sensory and chemical drivers behind consumer preference in the infant formula (IF) were analyzed. A total of 31 aroma-active compounds were identified, playing an important role in the production of off-flavors (especially fishy). Combined with the correlation analysis, the key aroma substances affecting the sensory attributes of IF were initially identified. A21, A22, B9 represented the key substances responsible for producing milky and creamy, while A2, A5, A11, A12, B5, C15, H5 primarily produced fishy. In addition, the two sensory attributes namely milky and creamy, and the T-sweet were more strongly correlated with consumer preference. Therefore, it can be concluded that consumers are more interested in the main flavor of the product than the off-flavor. These findings will inform the quality control of IF and the maintenance of sensory quality.

SERS determination of hydroxy-α-sanshool in spicy hotpot seasoning: The strategy to restrain the interference of capsaicin and its mechanism.

Hydroxy-α-sanshool (α-SOH) is the principal ingredient responsible for the numbing sensation in spicy hotpot. However, utilizing surface-enhanced Raman scattering (SERS) to analyze the α-SOH in hotpot seasoning is challenging due to the significant interference of capsaicin (CAP). Therefore, two schemes were proposed to address CAP interference in hotpot seasoning, namely laccase-catalyzed conversion and metal-organic framework (MOF) interaction. Among them, Fe-BTC MOF exhibited significant anti-interference effect and the underlying mechanism is elucidated. The motion of CAP aromatic ring was constrained by steric hindrance and electrostatic interactions of Fe-BTC. Additionally, the interaction between CAP aromatic ring and conjugated triene group in α-SOH was quenched, enhancing the α-SOH SERS signal. The proposed method had a significant anti-interference effect on α-SOH quantification in the presence of CAP, significantly enhancing the α-SOH SERS signal in a range of 0.85 to 4.00 × 107. The linearity and reproducibility of the proposed hotpot seasoning testing method were also validated.

Sensory Evaluation and Model Prediction of Vacuum-Packed Fresh Corn during Long-Term Storage.

The postharvest shelf life of fresh corn largely depends on the packaging method and storage temperature. This study investigated the effect of vacuum packaging (VP) with high-barrier (HB) or ordinary (OR) nylon/nylon/polypropylene (PP) composite films and the impact of storage temperature (4, 25, and 38 °C) on the shelf life of fresh corn. The sensory quality and color changes of the corn were evaluated, indicating a significant improvement in the glossiness (GL), sourness (SO), and color changes compared to corn packaged using OR films. The results showed that the HB films preserved corn freshness under refrigerated and normal temperature storage conditions, delaying color changes and SO development. A shelf-life model was established based on the Arrhenius equation. The predicted values of the corn at different temperatures were compared with the experimental data, indicating that the model could accurately predict the shelf life. The shelf life observed via sensory evaluation was more than 50% shorter than the results obtained by instrumental measurements. Therefore, sensory evaluation could be applied to determine shelf life and avoid food waste.

The contribution of subliminal perceptions, dietary habits, and psychological traits to the perception of oral tingling and burning sensations.

The tingling evoked by Sichuan pepper and the burning elicited by chili pepper constitutes the typical flavor of Sichuan cuisine and is a component of leisure food. Although factors affecting the burning sensation have extensively been studied, few studies have examined the factors of individual sensitivity, personality traits, and dietary habits that contribute to the perception of oral tingling sensation, which hinders the formulation of tingling products and the development of new products. In contrast, many studies have examined the factors influencing the burning sensation. In this web-based survey, 68 participants disclosed their dietary habits, liking for tingling and hot foods, and psychological traits. Individual sensitivity to the tingling and burning sensation produced by a range of Sichuan pepper oleoresin and capsaicin solutions was determined using rated differences from control, generalized labeled magnitude scale method and ranking test. The consistency score indicated the accuracy of individual ranking results while also providing an indirect response to the sensitivity of the participant to supra-threshold for burning or tingling. Individual ratings for medium Sichuan pepper oleoresin concentrations significantly correlated with the just noticeable difference (p < 0.01), and ratings for medium and high capsaicin concentrations correlated significantly with 6-n-propylthiouracil ratings (p < 0.01). Notably, the power exponent of burning was significantly correlated with the burning recognition threshold (p < 0.01), and the power exponent of tingling and burning were significantly correlated (r = 0.340, p < 0.05). There was a negative correlation between supra-threshold tingling and burning sensation perceptions and life satisfaction ratings. Further, intensity ratings for oral tingling and burning sensation did not always correspond with individual sensitivity indicators (e.g., recognition threshold, 6-n-propylthiouracil, just noticeable difference, and consistency score). Thus, this study provides new insight into establishing a sensory selection method for chemesthetic sensation panelists and theoretical guidelines for formulation design and in-depth analysis of popular tingling dishes and foods.

Monitoring volatile changes in infant formula during long-term storage at room temperature.

This study combined gas chromatography-mass spectrometry (GC-MS) and odor activity value (OAV) assessments to analyze the volatile ingredient changes in formula powder during 11 months of storage at room temperature. Orthogonal partial least squares-discriminant analysis (OPLS-DA) and variable importance in projection (VIP) were also used to assess the potential indicators of aroma changes during storage. The aim was to expose the possible changes in the aroma profile and the substances that alter infant formula (IF) aroma during storage. The results showed that the aldehyde and ketone content in the milk formula increased as the storage time was extended, while the lactone and terpenoid levels decreased significantly. The OAV indicated the presence of various major aromatic substances at different storage times. Considering consumer concern regarding product flavor, this study ascertained that monitoring substance changes during storage showed that 2-heptanone was a good indicator of milk flavor, dimethyl disulfide was a suitable indicator of protein degradation, and 3-methylbutanal, heptanal, hexanal, pentanal, and octanal were all good indicators of fat oxidation. The results of previous related studies were used to supplement the data in this work regarding the changes in IF during product shelf life and to provide support for controlling the flavor substances and quality during new product development.

Saltiness enhancement by "má là" umami flavor in NaCl model aqueous and oil-added systems.

The health concerns associated with high dietary sodium and the quest for a sensory experience have prompted the need for new strategies that can reduce the salt content of foods and have good acceptability. To investigate the cross-modal interaction effects of "má là" umami flavor (total of eight carriers) on the saltiness perception and effective sodium reduction in low-to-strong NaCl aqueous solutions (0.203 %-1.39 %) and oil-added systems (5 %, 10 %, 15 %, 20 %, 25 % canola oil, wt%), sixteen assessors were selected and two methods including saltiness intensity comparison with a category scale and rating with a generalized Labeled Magnitude Scale (gLMS) were used. The results showed PnSnUn carriers significantly enhance saltiness at moderate-to-strong NaCl solutions, and higher saltiness intensity with the addition of canola oil, especially at 25 % oil level. In addition, based on the developed Stevens' power function the sodium reduction was calculated, it was evident that two "má là" umami flavor combinations (one flavor combination was low "má", low "là" and moderate umami, and the other flavor combination with moderate "má", low "là" and moderate umami) were found to perform best with maximum sodium reduction of 18.88 % and 18 %, respectively, and when incorporating 25 % canola oil, the maximum sodium reduction raised by approximately 10 % (to 28.00 % and 28.42 %). This research not only confirmed the positive modulating effect of the "má là" umami flavor on saltiness perception in NaCl solutions, but also showed that the presence of oil further enhanced this effect. This work offered a new and promising insight into the development of foods with reduced sodium content while maintaining the saltiness properties.

Sensory Description and Consumer Hedonic Perception of Ultra-High Temperature (UHT) Milk.

Sensory characteristics of products play an essential role on the consumer' s acceptability, preference and consuming behavior choice. The sensory profiles and consumer hedonic perception for 14 UHT milk products using sensory quantitatively descriptive analysis and a 9-point hedonic scale were investigated in this study. There were significant differences in the sensory attributes intensity and liking scores among the organic whole milk, ordinary whole milk, low-fat milk, and skimmed milk (p < 0.05). Skimmed milk samples had lowest intensity scores of typical milk aroma, taste flavor and texture attributes, as well as had the lowest overall liking scores. Whole milk samples had higher sensory intensity scores than low-fat milk samples, even though no significant differences of overall liking scores were observed between whole milk and low-fat milk. Furthermore, the relationship between the sensory attribute and overall liking was demonstrated according to correlation analysis and partial least squares regression (PLSR) analysis. Overall liking increased significantly with the increasing of sweet, after milk aroma, protein-like, mellow and thick, while decreased significantly with the enhancement of cowy, cooked and whey (p < 0.05). These findings presented a potential strategy for identifying the key sensory attributes responsible for liking score differences among different kinds of UHT milk products.

The enhancement of the perception of saltiness by umami sensation elicited by flavor enhancers in salt solutions.

Health concerns related to the intake of salt have encouraged the investigation into sodium reduction by examining the taste-taste interaction between the perception of saltiness and umami. The effect of saltiness enhancement and sodium reduction of four kinds of umami carrier (WSA, MSG, IMP, and I + G) in a salt model solution with different salt concentrations (2.03-13.94 g/L) were investigated using the two-alternative forced-choice (2-AFC) and generalized Labeled Magnitude Scale (gLMS). The saltiness difference thresholds (DT) under different umami carrier were further explored using the constant stimuli method. The results showed that umami carriers had effective effects of saliness enhancement in the salt solutions with different concentrations, and higher enhancemen levels were obtained at larger salt concentrations. The level of saltiness enhancement were varied between the different umami intensity and carriers, and WSA carrier with moderate intensity had the maximum sodium reduction percentages which reached to 24.25%. Besides, the DT values of saltiness taste were increased under umami carrier, which means that more salt can be reduced without evoking a variation in saltiness. The present work not only provided insight into the effect of umami chemicals on the saltiness perception and saltiness DT values but also presented valuable information regarding flavor when developing low sodium foods and contributing to the development of more healthful products that meet current nutritional recommendations.

Geographical origin determination of Red Huajiao in China using the electronic nose combined with ensemble recognition algorithm.

Red Huajiao was the most important Zanthoxylum species in China, and its quality was highly determined the geographical region. This study was aimed to establish a determination method for the geographical origin recognition of Red Huajiao by using the electronic nose and ensemble recognition algorithm. Six origins of samples were detected by the electronic nose, and two categories of electronic nose sensors characteristic values, named as "optimized characteristic value" and "filtered characteristic value," were obtained by the principal component analysis and discrimination index method and Filter-Wrapper method. Based on the two categories of characteristic values, 22 kinds of model analysis methods, which belonged to five categories of ensemble recognition algorithms were used to recognize the geographical origin. The total recognition accuracy rate of the two categories of characteristic values were 83.9% and 85.7%, respectively. Furthermore, during 22 kinds of model analysis method, the ensemble Subspace KNN and Bagged Trees methods in Ensemble Learning algorithm exhibited the best distinguishing ability with the accuracy rate more than 90%. Therefore, the electronic nose combined with Ensemble Learning would be promising for the geographical origin determination application. PRACTICAL APPLICATION: This work demonstrates that the Red Huajiao can be simply and rapidly determined by using electronic nose combined with ensemble recognition algorithm, allowing to effectively distinguish geographical origin of Red Huajiao, which can provide an important reference for the quality assessment of Huajiao.

The influence of NaCl on the dynamic perception of the pungency sensation elicited by Sichuan pepper oleoresins.

A cross-modal interaction may exist between the perception of saltiness and the pungency elicited by Sichuan pepper oleoresin (Spo). Thirty-one hypersensitive panelists were selected to participate in this study. Spo solutions dissolved in different NaCl concentrations, ranging from 1.25 g/L to 167.9 g/L, were used as the test samples. The rated difference from control, the generalized labeled magnitude scale (gLMS), and the time-intensity (TI) method were used to determine the detection threshold (DT), the recognition threshold (RT), the intensity, and the dynamic perception of pungent sensation. The results revealed that the pungency thresholds increased significantly (p < 0.01) in the solution with a high NaCl (167.9 g/L) concentration. Furthermore, high NaCl solutions suppressed the pungency intensity at all Spo concentrations except for 0.02 g Spo/L in water (p < 0.05). The TI and principal component analysis (PCA) results showed that an increase in the Spo concentration prolonged the duration of the pungency sensation. However, the maximum intensity, the time to reach maximum intensity, the decay time of perception, and the end time of perception of the Spo solutions ranging from 2.13 g/L to 4.69 g/L were significantly reduced at medium (42.95 g/L) and high NaCl concentrations. Since the salty and pungency sensations exhibited by NaCl and Spo are common flavor combinations in food products and dishes, studying the influence of saltiness on the dynamic perception of pungent sensation not only aids the development of oral cleaners during pungency evaluation but also presents significant theoretical and practical value in creating pungent food and cuisine based on consumer preferences.

Interactions between Phenols and Alkylamides of Sichuan Pepper (Zanthoxylum Genus) in α-Glucosidase Inhibition: A Structural Mechanism Analysis.

The phenols and alkylamides in 26 varieties of Zanthoxylum pericarps (ZP) were comparatively identified, and the contribution of these key components to the inhibition of in vitro α-glucosidase (α-Glu) was confirmed using principal component analysis (PCA) and ingredient recombination models. Additionally, spectrophotometric assays, nuclear magnetic resonance (NMR), and molecular docking (MD) were employed to characterize the interactions among key components in ZP when exposed to α-Glu. Four phenols and hydroxy-α-sanshool (α-SOH), which were recognized as main ingredients, presented an antagonistic effect in the inhibition of α-Glu. 1H NMR demonstrated chemical shifts of certain hydrogens in the B phenolic ring and tetraenyl group, indicating a possible p-π conjugation between phenols and α-SOH. In addition, using MD analysis, the phenol-binding sites were observed to be negatively affected when α-SOH initially interacted with α-Glu. The combined results of the NMR and MD clarified the structural mechanism behind phenol/α-SOH antagonistic behavior in α-Glu inhibition.

The enhancement of the perception of saltiness by Sichuan pepper oleoresin in a NaCl model solution.

Health concerns related to the intake of salt have necessitated the investigation into NaCl reduction by examining the cross-modal interaction between the perception of saltiness and pungency elicited by Sichuan pepper oleoresin (Spo). The category scale and the generalized Labeled Magnitude Scale (gLMS) were used to determine the degree to which Spo enhanced the perception of saltiness in the NaCl model solution. Sixty-eight participants were divided into the hyposensitive, semi-sensitive, and hypersensitive groups according to individual exponent. The power functions of saltiness under different pungency carriers were obtained. The level of enhancement varied between the different sensitivity groups and pungency carriers. In the hypersensitive group, the low and strong pungency carriers effectively enhanced the perception of saltiness at low to moderate, and moderate to strong NaCl solutions, respectively. In the semi-sensitive group, low and moderate pungency carriers induced additive effect in the perception of saltiness at full and moderately strong NaCl solutions, respectively. However, the additive effect was inadequate in the hypo-sensitive group. Therefore, the low pungency solution was more feasible for enhancing in the perception of saltiness, while the maximum NaCl reduction percentages corresponded to the hypersensitive and semi-sensitive groups at 38.61% and 39.06%, respectively. This research not only provided insight into the effect of pungency on the perception of saltiness as it related to individual sensitivity, but also presented valuable information regarding flavor when developing food with reduced salt content.

Tsinghua facial expression database - A database of facial expressions in Chinese young and older women and men: Development and validation.

Perception of facial identity and emotional expressions is fundamental to social interactions. Recently, interest in age associated changes in the processing of faces has grown rapidly. Due to the lack of older faces stimuli, most previous age-comparative studies only used young faces stimuli, which might cause own-age advantage. None of the existing Eastern face stimuli databases contain face images of different age groups (e.g. older adult faces). In this study, a database that comprises images of 110 Chinese young and older adults displaying eight facial emotional expressions (Neutral, Happiness, Anger, Disgust, Surprise, Fear, Content, and Sadness) was constructed. To validate this database, each image was rated on the basis of perceived facial expressions, perceived emotional intensity, and perceived age by two different age groups. Results have shown an overall 79.08% correct identification rate in the validation. Access to the freely available database can be requested by emailing the corresponding authors.

[Analysis of NIR characteristic wavelengths for apple flesh firmness based on GA and iPLS].

In the present study, the fruit flesh firmness of apple was analyzed by near infrared (NIR) spectroscopy using an FT-NIR spectrometer. The sensitive spectral regions that provide the lowest prediction error were analyzed by different well-known variable selection methods, including dynamic backward interval partial least-squares (dynamic biPLS), sequential application of backward interval partial least-squares and genetic algorithm(dynamic biPLS & GA-PLS), and iterative genetic algorithm partial least-squares (iterative GA-PLS). Iterative GA-PLS, dynamic biPLS & GA-PLS led to a distinct reduction in the number of spectral data points with better predictive quality. Furthermore, the majority of selected wavelengths were content with the characteristic of the sorption bands of fruit flesh firmness. Pectin constituents, complex non-starch polysaccharides, which are related to texture change in apple, play an important role in their harvest maturity, ripening and storage. Comparing NIR characteristic wavelengths of apple flesh firmness and typical absorption bands for pectin, it was found that characteristic wavelengths of apple flesh firmness were consistent with the pectins relevant spectral regions. Therefore, the NIR characteristic wavelengths of apple firmness based on GA and iPLS reflected the chemical component of apple and the results were reasonable.

[Using GA-dOSC method to eliminate interference of peel with prediction of apple firmness based on near infrared diffuse reflection spectra].

In the present work, "Fuji" apples from Shandong Yantai were used to take the diffuse reflection spectra by FT-NIR PLS components (i.e., factors) were computed by nonlinear iterative partial least squares (NIPALS) and the number of latent factors (LV) was optimized by a leave-one-out cross-validation procedure on the calibration set. On the basis of partial least square (PLS) regression, the models for apples' firmness before and after peeling were compared. In order to eliminate the effect of apple peel on prediction, spectral pretreatments such as multiplicative scatter correction (MSC), derivative, direct orthogonal signal correction (DOSC) and wavelengths selection based on genetic algorithms (GA) were used. Finally, the results of different spectral treatments were compared. In conclusion, the RSDp of models for apples before and after peeling was 16.71% and 12.36%, respectively, suggesting that the apple peel played a negative role in constructing good predictive models. Moreover, the traditional spectral pretreatments (such as MSC, derivative) can hardly resolve the problem. In this research, GA-DOSC played an important role in reducing the interference of apple peel. It not only reduced the wavelength variables from 1480 to 36, but also reduced the latent variables from 5 to 1. The correlation coefficient (r) was improved from 0.753 to 0.805, and the RMSECV and RMESP were reduced from 1.019 kgf x cm(-2) and 1.197 kgf x cm(-2) to 0.919 kgf x cm(-2) and 0.924 kgf x cm(-2), respectively. Especially, the RSDp was decreased remarkably from 16.71% to 12.89%. The performance of the model after GA-DOSC treatment was similar to the model using spectra of apple flesh (12.36%). It was concluded that the prediction precision based on GA-DOSC satisfied the requirement of NIR non-destruction determination of apples firmness.