Hydroxymethylfurfural Content Research Articles

Changes in bioactive compounds and antioxidant activity of Gaziantep and Kastamonu garlic during black garlic production

Garlic (Allium sativum L.), a member of the Alliaceae family, has been widely used in cuisine and traditional medicine since ancient times. Black garlic is produced by fermentation of fresh garlic under controlled conditions for a certain period at high temperature (60-90°C) and high humidity (70-90%). According to the Turkish Statistical Institute (TURKSTAT) data, Kastamonu and Gaziantep garlic varieties are the most cultivated garlic varieties in our country. Changes in protein, sugar content, antioxidant capacity (DPPH and ABTS methods), total phenolic content, 5-hydroxymethylfurfural (HMF) content, and organosulfur compound profiles were investigated in samples taken from Kastamonu and Gaziantep fresh garlic at 7, 14, 21, and 28 days of black garlic production under 65°C temperature and 70% humidity conditions. With these analyses, the differences between black garlic and fresh garlic and the changes in black garlic during the production process were revealed in detail. It was determined that the amount of total phenolic content and antioxidant capacities increased in the black garlic production processes of both regions compared to fresh garlic. While sucrose was fresh garlic’s dominant sugar, fructose was black garlic’s dominant sugar. Among the organosulfur compounds, allicin was dominant in fresh garlic and SAC in black garlic. It was determined that SAC was formed after the enzymatic conversion of ɣ-glutamyl-S-alk(en)yl-L-cysteine and ɣ-glutamyl and the temperature and fermentation time used in black garlic production increased the formation of SAC. The protein content ranging between 5.8%-7.3% in fresh garlic was 13.1-14.2% in black garlic. Fresh and black garlic from the Gaziantep region was determined to have higher total phenolic content, antioxidant capacity, and organosulfur compound contents.

The High Pressure Preservation of Honey: A Comparative Study on Quality Changes during Storage.

In commercially available honey, the application of a heat treatment to prevent spoilage can potentially compromise its beneficial properties and quality, and these effects worsen with extended storage. The high-pressure processing (HPP) of honey is being explored, but its long-term impact on honey quality has not been characterised yet. This study evaluated the effects of HPP and thermal processing on the microbial load, physicochemical quality (i.e., hydroxymethylfurfural content and diastase activity), and antioxidant capacity of honey after treatment and following extended storage (6, 12, and 24 months) at 20 °C. Pasteurization (78 °C/6 min) effectively eliminated the microorganisms in honey but compromised its physicochemical quality and antioxidant activity. HPP initially showed sublethal inactivation, but storage accelerated the decrease in yeasts/moulds and aerobic mesophiles in honey (being <1 log CFU/g after 24 months of storage) compared to unprocessed honey and honey thermally treated under mild conditions (55 °C/15 min). The physicochemical characteristics of the quality of HPP-treated honey and raw unprocessed honey did change after long-term storage (24 months) but remained within regulatory standards. In conclusion, HPP emerged as a more suitable and safe preservation method for Apis mellifera honey, with a minimal risk of a loss of antioxidant activity compared to traditional industrial honey pasteurization.

Physico-chemical properties of multifloral honey Apis dorsata and monofloral honey of bees Apis mellifera

Physicochemical properties of honey as one of the information about the quality of honey. The type of bee, geographic location, and type of vegetation the source of the honey bee feed influence the physico-chemical properties of honey. This study aims to determine the physico-chemical properties of multifloral honey of Apis dorsata bees and monofloral honey of Apis mellifera bees. The honey samples for this study consisted of 4 multifloral honey samples and 4 monofloral honey samples. Physicochemical parameters of honey include water content, color, pH, acidity, reducing sugars, and hydroxymethylfurfural (HMF). Data were analyzed descriptively and quantitatively. The results of the analysis showed that most of the research honey had a water content above the SNI 8664-2018 standard. Honey that has high levels is easy to ferment and to overcome this by lowering the water content of honey through a dehumidifier. Monofloral honey has an intensity value of 47 to 143 mm Pfund, while multifloral honey has 74 to 100 mm Pfund. The pH value of honey ranges from 3.5 to 4.5. The level of acidity, reducing sugar content, and HMF content of all honey samples in the study complied with SNI-8664. There are differences in the physical and chemical characteristics of multifloral honey and monofloral honey.

Comparison of different drying methods for bergamot peel: Chemical and physicochemical properties.

This study examines the effectiveness of seven drying methods applied to bergamot peels, encompassing hot air, microwave, infrared-assisted microwave, freeze, infrared, sun, and oven drying. All samples exhibited moisture content and water activity levels within the acceptable range for dry foods. All methods effectively transformed the peels into powdered form, yielding comparable results. Each method offers distinct advantages and disadvantages, and the choice of method should be based on the desired properties of the final product. The highest ascorbic acid content was found in freeze-dried and hot air-dried samples (>400mg/100g), whereas sun-dried samples had the lowest (89.58mg/100g). Infrared-dried samples exhibited the highest levels of total phenolics and flavonoids (193.40 and 530.14mg/100g, respectively), attributed to reactions induced by elevated temperatures. The total carotenoids were higher in freeze-dried samples (54.12mg/100g) compared to other drying methods (<27mg/100g). Microwave-dried samples had the highest 5-hydroxymethylfurfural content (73.06mg/100g), and freeze-dried samples had the highest naringin content (1568.70mg/100g). Although infrared drying had good particle density, porosity, and fluidity, freeze-drying was the most effective, retaining the highest levels of bioactive compounds. Among the methods studied, freeze-drying is recommended due to its superior ability to preserve bioactive compounds. Infrared and infrared-assisted drying methods were suitable for recovering phenolics from bergamot waste, offering lower energy consumption and practical preservation of physicochemical properties. This study emphasizes the importance of selecting the appropriate drying method to ensure high-quality dried food and producing value-added products from bergamot waste, contributing to sustainable agriculture and waste reduction. PRACTICAL APPLICATION: This study demonstrates that infrared and freeze-drying are the most effective methods for producing high-quality bergamot peel samples with enhanced antioxidant properties. These findings hold promising implications for the food industry, offering a viable approach to preserve bergamot peels and their valuable attributes.

Effect of ultrasound technique to improve quality of Iranian industrial honey by controlling crystallization process.

This experiment aimed to assess the effects of ultrasound techniques on the quality of Iranian industrial honey. Honey samples were subjected to ultrasound waves at different frequencies and various parameters. The results showed that both ultrasound treatments (30 or 42 kHz) changed the physical, biochemical, antioxidant, and antibacterial characteristics of honey. Ultrasound treatments at 20 or 45°C for 1, 5, or 10 min reduced moisture, acidity, sugars, ABTS levels, 5-hydroxymethylfurfural content, clostridium, aerobic mesophilic bacteria count, and osmophile count while increasing diastase, phenol, and proline levels. Ultrasound treatment of honey samples at 30 and 42 kHz and different temperatures for varying durations led to a decrease in acidity after 90 and 180 days. Treating honey samples with 42 kHz ultrasound at 45°C for 10 min led to a significant reduction in the amount of reducing sugar. Ultrasonication at different frequencies and temperatures led to higher levels of phenol, ABTS, and proline production, along with a considerable decrease in the total count of aerobic mesophilic bacteria. Our study unveils the potential of ultrasonication to enhance honey quality through multifaceted improvements. Treatment significantly augmented phenolic content and antioxidant capacity, opening avenues for novel honey preservation and quality enhancement strategies. Additionally, ultrasonication effectively controlled honey crystallization while simultaneously improving biochemical, antioxidant, and antibacterial properties. This demonstrates its potential as a comprehensive strategy for honey quality improvement.

Hydroxymethylfurfural content of old honey samples – Does the sticky treat really last forever?

Honey is thought to be a food source with indefinite shelf life - this statement is questioned in present work by analysing the 5-hydroxymethylfurfural (HMF) content of a unique series of old honeys from 1959 to 2020. Two special series are included where honey was produced and kept yearly by the same beekeeper for 30 years. Application development was carried out for White method by scaling down the volumes for the analysis. The HMF content of acacia honeys vary in a wide range (9–1320 mg/kg honey), but tendentially increase with age. However, rape and sunflower honeys show a remarkably high offset compared to the expected trendline and there is no observable pattern in their HMF level plotted against the year of collection. Even the youngest rape and sunflower honeys exceeded the threshold limit of 40 mg/kg and only acacia samples collected after 2015 remained below the accepted health value.

Effect of high DHA and ARA fortification on non-enzymatic browning of infant formula powder

ABSTRACT To investigate the effect of adding high-dose docosahexaenoic acid (DHA) and arachidonic acid (ARA) on the stability of infant formula powders (IFs), IFs fortified with high-dose and low-dose DHA and ARA were compared and evaluated during storage at 37°C for six months. We specifically focused on the changes to IFs caking, amino acid content, and 5-hydroxymethylfurfural (HMF) content. We found that during the storage process, there was no significant change in the amino acids of IFs following supplementation with high- or low-doses of DHA and ARA. However, HMF and color difference (∆E) increased with the length of storage time. A comparison between the high-dose and low-dose groups revealed that the addition of high-dose DHA and ARA did not cause an additional increase in the HMF but exacerbated the caking of IFs. The addition of high-dose DHA and ARA did not exacerbate the non-enzymatic browning of IFs.

Changes in quality and bacterial profiles of Tualang and Kelulut honeys preserved by post‐harvest maturation

SummaryPost‐harvest maturation of two Malaysian honeys, the Tualang and Kelulut was studied by measuring changes in physicochemical and antioxidant properties, hydroxymethylfurfural (HMF) contents and bacterial profiles at room temperature of 23–26 °C. After maturation at the recommended period of 26 weeks, water activity of both honeys increased between 0.89% and 2.34% while free acidity increased between 2.05% and 2.24%. Results suggested the prominence of fermentation reactions in honey during post‐harvest maturation as fructose concentration reduced by 10.6% and 1.05% for the Tualang and Kelulut honey, respectively, while HMF concentrations were kept at a safe limit of 48.00 and 61.23 mg/kg honey. The total phenolic content of Tualang and Kelulut honey increased significantly by 12.61% and 54.66% respectively. The highlight of this post‐harvest maturation process for Kelulut honey was the improvement found in antioxidant properties of DPPH radical scavenging activity by 10.01%–54.74% and also the probiotic‐like potential in terms significant increase in relative abundance of the Bacillus genera to 2.6% and Lactobacillus to 6.25% at 26 weeks. The prolonged maturation process up to 1 year however revealed continuous accumulation of HMF to values above 80 mg/kg honey, surpassing the limits by the Codex Alimentarius Commission despite improvements of antioxidant properties and bacterial profiles.

Exploring geographical influences on physicochemical characteristics of honey: the Montesinho Natural Park scenario

Abstract Objectives In recent years, there has been a substantial increase in the global consumption of honey, driven by the high demand for natural products that offer health benefits. Consequently, consumers show a preference for honey, recognised for its superior quality, namely honey with a Protected Designation of Origin (PDO) or honey produced in protected areas, as it is associated with superior attributes and characteristics. Portugal is one of the leading countries in the production of PDO honey, with Montesinho Natural Park (MNP) being an excellent example of high-quality Portuguese honey, known for its distinctive attributes. However, environmental threats pose a double challenge, leading to a decline in honey production and compromising its overall quality. This study aimed to assess the specific physicochemical parameters and nutritional characteristics of MNP honey and investigate their correlation with the different locations of apiaries. Materials and Methods MNP honey samples (n=13) were obtained from local producers or purchased at supermarkets. Standard physicochemical parameters, such as 5-hydroxymethylfurfural, diastase activity, moisture and ash content, free acidity, electrical conductivity and pH, were determined according to honey legislation. Additionally, colour parameters, protein, low-molecular-weight carbohydrates (mono- and disaccharides), and mineral content were determined. Results The results obtained were consistent with the requirements outlined in the legislation and those described in the literature. The results suggest that geographical factors within the park and boundaries do not contribute to variations in the analysed parameters. Conclusions A significant level of homogeneity was evident in all parameters evaluated among the MNP honey samples. This is the first comprehensive study of the physicochemical properties of honey from various apiaries within the MNP.

Diastase Enzyme activity and Hydroxymethylfurfural production during thermal processing of honey

The thermal treatment of honey is used to prevent honey crystallization which is one of the main problems that face beekeepers. In this study three samples of honey were heated at 40, 60, 80 and 100 °C, as a function of time in hours (h). Heating the samples at 40 °C did not show any significant effect on hydroxymethylfurfural (HMF) production or diastase enzyme activity up to 95 hours. Heating to higher temperatures 60, 80 and 100 °C resulted in a regular increase in HMF content and drop-off in diastase activity as a function of time. The HMF content reached 40 mg/kg after 80, 12.5 and 6 hours. For the three samples at 60, 80 and 100 °C respectively. Conversely, diastase enzyme activity reached close to 8 IU after 96, 12.5 and 5 hours. For the following temperatures 60, 80 and 100 °C respectively. The results showed that heating temperatures up to 40 °C is safe for long-term storage, while heating at 60 °C could be used but for a shorter treatment time. Results showed that the must temperature does not exceed 60 °C for 5 hours or 80 °C for one hour to preserve the honey's quality. The reaction rate constants and activation energy Ea of HMF formation in three samples were found 83.07, 91.79 and 89.57 kJ.mol-1 respectively. Therefore, honey can be preserved in this way, while at the same time the HMF remains below the permissible values, and the enzymatic activity remains at its highest level.

Evaluation of safety and quality parameters of persimmon balsamic-type vinegar during multistarter culture fermentation and accelerated aging with oak chips

The present study explores for the first time, the feasibility of using concentrated persimmon juice (CPJ) as a starting material for high-quality balsamic-type vinegar (cv. Jiro, Northern Greece) via a two-stage fermentation process (alcoholic fermentation and then acetification). The best-performing wild type osmophilic strains of Hanseniaspora uvarum and Saccharomyces cerevisiae and acetic acid bacteria isolated from concentrated grape must and varietal vinegar (cv. Xinomavro, Northen Greece), respectively, were used as multistarters. The objective was to produce persimmon balsamic vinegar (PBV) that could be subsequently aged using oak chips as an accelerating agent under conditions that promote its quality attributes. A Taguchi design was applied to reveal the most influential combination of process factors (oak chips amount and pretreatment, aging time) as to the desired sensorial and physicochemical characteristics of the aged PBV (saturated and clear red-orange color, balanced ratio of sugars/organic acids, low 5-hydroxymethyl furfural (HMF) content, high antioxidant activity). Notably, adding even very low amounts (1% w/v) of oak chips significantly affected the quality profile of PBV within a very short aging time (10 days). After 30 days, PBV presented distinct, attractive color characteristics regardless of the amount or pretreatment of oak chips. The HMF content remained constantly low during all treatments while the redox potential increased on intensification of conditions. Implications for the role of phenolic compounds and/or other component interactions with oak chips are discussed. Our approach and outcomes contribute to the innovative valorization of persimmon fruits and the development of aged persimmon balsamic vinegar.

A Novel HPLC Method for Rapid Determination of HMF in Dulce de Leche: A Potential Tool for Quality Control

A validated isocratic method utilizing reverse-phase high-performance liquid chromatography (RP-HPLC) was developed for the quantification of hydroxymethylfurfural (HMF) in five distinct commercially available Dulce de Leche samples that are sold in Turkish markets. The X-Terra RP-18 column, which has dimensions of 150 × 4.60 mm i.d. and a particle size of 5 μm, was selected for the stationary phase. The separation process was conducted isocratically by utilizing a methanol-water mixture (10:90, v/v) containing 1% TCA as the mobile phase. The separation was carried out at a temperature of 25 oC and a flow rate of 0.5 mL/min. The detection was performed at a wavelength of 284 nm. The methodology exhibited favorable selectivity and linearity, as evidenced by a correlation coefficient (r) exceeding 0.999. The obtained values for the limit of detection (LOD) and limit of quantification (LOQ) were 0.0019 μg/mL and 0.0059 μg/mL, respectively. Additionally, the recovery rate was determined to be 95.45%. Furthermore, it has been reported that the levels of HMF in commercially available Dulce de Leche originating from Turkey vary between 50.55 and 90.18 mg/kg for the total HMF content.

Physicochemical, Rheological, and Thermal Properties of Pot-Honey from the Stingless Bee Melipona beecheii

The availability of data on physicochemical properties is crucial to direct efforts towards identifying the quality standards of the Neotropical stingless bee Melipona beecheii’s pot-honey. In this vein, other properties apart from those typically considered for Apis mellifera could also be relevant in characterizing the honey of this stingless bee. The physicochemical, rheological, and thermal properties of pot-honey from Melipona beecheii (Yucatán, México) were analyzed. Samples were collected from two annual harvests (2018 and 2019) and from a rural and an urban location. Free acidity, moisture, total reducing sugars, diastase activity, hydroxymethylfurfural content, and electrical conductivity were measured using standard techniques. The rheological and thermal behaviors were determined via Couette rheometry and differential scanning calorimetry, respectively. The physicochemical properties of Melipona beecheii pot-honey can be incorporated into a general quality specification for honey of the Neotropical Melipona genus, or as the basis for a regional (Mesoamerican) standardization of honey from this particular bee species. The rheological analyses indicated the Newtonian behavior of Melipona honey in the full studied range of 10-40 °C (7,545-244 cp), showing dynamic viscosities significantly lower than those expected for Apis mellifera honey, primarily due to its high water content. Two main endothermic transitions were detected via differential scanning calorimetry: at 96-162 °C and at 169-230 °C. The Apis mellifera honey samples showed the same thermal transitions but differed from Melipona beecheii honey in their peak temperatures and enthalpies.

Characterization of Italian honeys: integrating volatile and physico-chemical data

This article focuses on the comprehensive characterization of Italian honeys using various physico-chemical analyses and their volatile organic compounds (VOCs) fingerprint obtained through the PTR-ToF-MS technology. Honey characteristics, including pH, electrical conductivity, moisture content, hydroxymethylfurfural (HMF), and sugar content, were analyzed to assess their quality and origin. Honey samples from different flowers, including acacia, chestnut, citrus, linden, and multifloral, were collected and investigated. Furthermore, a few aged honeys were collected and analyzed and compared with the fresh ones. Physico-chemical analysis revealed that chestnut honey is characterized by high pH and EC values. Acacia honey has a higher fructose content, while aging appears to influence HMF levels, a vital indicator of honey quality, with aged samples exhibiting significant increases in HMF content. The VOC profiles have been found to vary among different honey types, suggesting that VOCs could be used as indicators of honey origin. Multivariate statistical analyses, such as partial least squares discriminant analysis (PLS-DA), have been applied to the VOCs data to differentiate honey types based on their volatile profiles. Acacia honey exhibited different physicochemical parameters but on the contrary, in the VOCs analysis, it displayed similarities with the linden honey due to their shared low emissions of volatile compounds. Citrus honey had similar chemical parameters to linden and multifloral honeys, but its distinctive VOCs emission allowed for a more accurate identification. In conclusion, the analysis performed with the PTR-ToF-MS was successful in obtaining specific volatile fingerprints of those samples and was effective for improving the characterization of honeys.

Physicochemical homogeneity of stingless bee honey (Heterotrigona itama) produced in the west coast, east coast and inland area of Peninsular Malaysia.

The nutritional composition of stingless bee honey (SBH) can be affected by different climates and soil composition across different geographical areas. However, the range of attributes set for a honey quality standard should be inclusive. This study analysed the sugar profile's physiochemical properties, including quantifying the rare sugar trehalulose, organic acid and mineral composition of SBH collected from inland, and west and east coasts of Peninsular Malaysia. Forty-three SBH (Heterotrigona itama) samples were collected and labelled as <20 and <40 West Coast (<20WC, <40WC), <20 and <40 East Coast (<20EC, <40EC) and Inland, according to their distance from the coasts. The moisture, pH and sugar composition of all SBH samples adhered to the Malaysian Kelulut Honey Standard (MS2683:2017) but not to the International Codex Standard (CODEX) for honey. Trehalulose presence in all samples, regardless of geographical area, was predominant alongside fructose and glucose. Only hydroxymethylfurfural (HMF) content and electrical conductivity (EC) results complied with both standards. The principal component analysis biplot showed that the discrimination of SBH according to the five different areas was not feasible, indicating sample homogeneity. The physicochemical evaluation of SBH from Peninsular Malaysia shows mainly homogeneous attributes of samples across geographical locations. These findings demonstrated that the current MS2683:2017 is relevant and accommodates all SBH of H. itama species produced in Peninsular Malaysia. Furthermore, the trehalulose range calculated in this study can be implemented as a new benchmark for the indicator of SBH honey quality standard by national and international food standard committees. © 2023 Society of Chemical Industry.

Impact of Pretreatment and Drying Factors on Chemical and Biochemical Attributes of Moroccan Thompson Seedless Grapes.

Drying is a common technique in the agrifood industry, but insufficient control in the drying process can result in changes to the fruit's appearance due to physiological damage during processing. The aim of this study was to investigate the impact of pretreatment and drying process parameters on Moroccan raisins' quality and safety. The experimental levels of pretreatment factors (blanching, browning agents) and drying temperature were defined at the beginning. Subsequently, a 24-factorial design was employed to provide a simple and reliable model capable of relating directly the response factor (drying time, color intensity change (E∗), chromaticity (C∗), and browning rate) to the variables (NaOH concentration, antibrowning agent concentration, temperature, and relative humidity). All four parameters had a statistically considerable effect on studied responses. Blanching for 5 minutes at 1% of NaOH solution, using an appropriate concentration of antibrowning agent (5% Na2S2O5), and drying at 70°C with 30% of relative moisture can lead to better preservation of grapes' appearance and quality (chromaticity (C∗) and color change (E∗)). Also, in these conditions, a lower browning rate (14.48%), a lower 5-hydroxymethylfurfural content (12.40 mg/100 g DW), and a higher level of polyphenols (135.79 ± 13.17 mg GAE/100 g DW) and flavonoid content (57.81 ± 3.08 mg Qeq/100 g DW) have been recorded while meeting international standards for SO2 content and microbial quality.

Study of the Physiochemical and Nutraceutical Properties of Sour and Sweet Pomegranate Juice in Northern Jordan

Pomegranate juice (PJ) is the major pomegranate product that offers a simple way to consume pomegranate’s biologically active compounds, obtained from arils. In this study, we objectively investigate the physiochemical properties such as pH value, total soluble solids, color parameters, fructose and glucose contents, hydroxymethyl furfural (HMF) content, and viscosity. Also, the phytochemical content includes total phenols content, antioxidant activity, flavonoid, anthocyanin content, and phenolic quantification. In addition, the alpha-amylase and angiotensin-converting enzyme inhibitory activities among sweet and sour varieties of pomegranate juice obtained from different regions in Northern Jordan (Ajloun, Dair Abi Said, and Kufur Soum) where the significant differences at P ≤ 0.05 appeared among sweet and sour varieties in different pomegranate juice samples. The pH values for pomegranate juice range from 2.87 to 3.77, and TSS ranges from 15.36 to 16.9 Brix. The total phenol content of pomegranate juice ranged from 105.8 to 238.63 mg/g while the total flavonoid content was present in the range of 135.53–184.9 mg/g. The DPPH inhibition (%) of pomegranate juice ranged between 20.66% and 50.63%, and the anthocyanin content range was 3.66–11.02 mg/g. Ellagic acid, delphinidin, 3,4-dihydroxyphenethyl alcohol, 2-hydroxyphenethyl alcohol, catechin, epicatechin, vanillic acid, caffeic acid, P-coumaric acid, chlorogenic acid, gallic acid, ferulic acid, and syringic acid are phenolics present predominantly in pomegranate juice. Pomegranate juice exhibits high alpha-amylase and angiotensin-converting enzyme inhibition activity. All results indicate good quality and health properties for pomegranate juice.

Quality changes and path analysis of color degradation of Dendrobium officinale flower juice during storage

The research was conducted to investigate the quality changes of basic physicochemical indicators, functional components and appearance, such as, pH, total color difference, Browning Index, polyphenols, flavonoids, anthocyanins, VC, and 5-hydroxymethylfurfural content and so on of Dendrobium officinale flower juice (DOFJ) under the dark storage conditions of 4, 25 and 37 °C and the natural light irradiation storage conditions of 25 °C for 8 weeks. Correlation and path analyses were used to analyze the causes of color degradation of DOFJ. Although measures had been taken during the preparation process to inhibit enzymatic browning by deactivating the activity of polyphenol oxidase (PPO), DOFJ was still unstable under four storage conditions, especially for color degradation. With the increase of temperature and time, the basic physicochemical indexes did not change significantly, but the content of functional components gradually decreased, and the appearance gradually deteriorated. The path analysis indicated that anthocyanins degradation was the key factor of color degradation of DOFJ, and low temperature and light protection could delay the degradation of anthocyanins. The main cause of color degradation of DOFJ during storage was identified, which provided a basis for further inhibiting color degradation of flower juice.

Detection of the 5-hydroxymethylfurfural content in roasted coffee using machine learning based on near-infrared spectroscopy.

Since 5-hydroxymethylfurfural (5-HMF) is carcinogenic to humans, its detection in foods is essential. This study performed near-infrared (NIR) spectroscopy (11998-4000cm-1) to determine the 5-HMF content in roasted coffee. The random forest (RF) was used to extract important wavenumbers, after which three machine learning models (ordinary least square (OLS), support vector machine (SVM), and RF) were established for the prediction. RF obtained the best prediction results (Rc2=0.98 and Rp2=0.92) compared with OLS and SVM and effectively extracted the important wavenumbers (11667cm-1, 11666cm-1, 10905cm-1, 7096cm-1, 7095cm-1, 7094cm-1, 7093cm-1, 7092cm-1, 5054cm-1, 5026cm-1, 5025cm-1, and 5024cm-1). The results demonstrated that machine learning models based on NIR spectroscopy could provide a non-destructive approach for determining 5-HMF content in roasted coffee.

Volatile compounds, antioxidant activity, ACE inhibitory activity, HMF content and microstructure of fruit yoghurts

Stirred-type fruit yoghurts with two different fruit purees (kiwifruit and banana) were produced and were investigated the physicochemical, volatile compounds, 2,2-diphenylpicrylhydrazyl (DPPH) free radical scavenging activity, cupric ion reducing capability (CUPRAC), total phenolic compounds (TPC), angiotensin-converting enzyme (ACE) inhibitory activity, 5-hydroxymethylfurfural (HMF) content, reducing sugar content and microstructure. The addition of fruit puree affected (p&lt;0.01) total solids, fat, protein, ash, L*, a*, b*, volatile compounds, DPPH, CUPRAC, TPC, ACE inhibitory activity, HMF content, reducing sugar content and overall acceptability whereas it had an insignificant effect on the pH, titratable acidity, apparent viscosity, syneresis (p&gt;0.05). Storage period significantly (p&lt;0.01) affected the titratable acidity, DPPH, CUPRAC, TPC, ACE inhibitory activity, HMF content, reducing sugar content and overall acceptability, as well as the pH, apparent viscosity and a* (p&lt;0.05). Although the addition of banana and kiwi relatively suppressed the characteristic flavour of the experimental yoghurt samples, it improved the DPPH, CUPRAC and TPC. On the other hand, the addition of banana-kiwi was found to increase the content of HMF, the toxic compound. Yoghurt can be recommended as an important source of bioactive compounds with ACE inhibitory activity. According to the microstructure analysis results, a more homogeneous structure was observed in the control group samples compared to the fruit-added yoghurt samples and it was determined that the serum pore diameters were smaller.