Thermally Sterilized Research Articles

Unraveling the key cooked off-flavor compounds in thermally sterilized green tea beverages, and masking effect of tea raw material baking

The occurrence of the cooked off-flavor during the thermal sterilization of green tea beverages negatively impacts their quality. This study aimed to identify the key cooked off-flavor compounds by molecular sensory science. The increase of 12 compounds, including malty (e.g., 3-methylbutanal), floral (e.g., linalool), sweet (e.g., methional), and smoky (2-methoxy-4-vinylphenol) compounds, contributed to the development of the cooked off-flavor. Additionally, the loss of five aroma compounds—dimethyl sulfide, (E)-β-ionone, 2-methylbutanal, 1-penten-3-one, and (E,Z)-2,6-nonadienal—also caused the emergence this undesirable flavor. One potential solution to reduce the cooked off-flavor was the baking of tea raw materials. While baking did not significantly reduce the concentration of off-flavor compounds, it led to an increase in eight roasty aroma compounds, such as pyrazines and pyrroles, which helped partially mask the cooked off-flavor in green tea beverages.

Unraveling the mechanism of alleviating the textural deterioration of thermally sterilized cooked noodles: Effect of gluten content and quality

Thermal sterilization is valuable for creating shelf-stable instant wet cooked noodles; however, it often leads to a poor texture. In this study, seven different reconstituted wheat flours were used to evaluate the impact of gluten content and quality on alleviating the textural deterioration of instant wet cooked noodles. Increasing the gluten content in wheat flour led to a higher hardness of instant wet cooked noodles, and the tensile distance significantly increased from 18.41 to 32.11 mm (p < 0.05). Conversely, as the glu/gli ratio decreased, the hardness decreased from 53.96 to 44.47 N, but the tensile distance significantly increased from 29.24 to 40.75 mm (p < 0.05). The rheological properties showed that a higher gluten content increased the elastic modulus at low strain and a lower glu/gli ratio reduced the deformation ratio at high strain. Size-exclusion high-performance liquid chromatography analysis revealed that less sodium dodecyl sulfate (SDS)-extractable glutenin was retained in the noodles with a high gluten content and more SDS-extractable gliadin was preserved at a low glu/gli ratio. The confocal laser scanning microscopy results showed that a high gluten content induced a compact network and a low glu/gli ratio in wheat flour resulted in a continuous network.

Using multi-criteria decision-making method to select the optimal color fixative for cloudy kiwi juice during thermal sterilization processing

Color deterioration is inevitable during the thermal sterilization of cloudy kiwifruit juice (CKJ), which seriously affects its sensory quality. This study explored the effects of citric acid, Ca(OH)2, CuSO4, and α-cyclodextrin on protecting the color and quality of thermally sterilized CKJ. Results showed that the all fixatives reduced the a*, L*, browning index (BI), and ΔE* of CKJ; significantly increased the h°, and effectively prevented the color deterioration of CKJ during thermal sterilization. Except for citric acid, none of the color fixatives changed the sugar-acid ratio of CKJ. Citric acid and α-cyclodextrin treatments significantly enhanced or considerably retained the nutritional quality and antioxidant activity of CKJ. Furthermore, three models of principal component analysis (PCA), entropy weight-TOPSIS and grey relation analysis (GRA) were established based on the multi-criteria decision-making (MCDM) method for comprehensive quality evaluation. The model composite score of CKJ treated with 6 g/kg α-cyclodextrin was the highest, and 0.6 g/kg citric acid was the lowest.

Identification of the key off-flavor odorants for undesirable spoiled odor in thermally sterilized fermented soymilk

Spoiled odors are a problem in thermally sterilized fermented soymilk. This study aims to clarify production conditions and key odorants of spoiled odors. The sensory evaluation showed that thermal sterilization caused a decrease in the sensory intensity of yogurt and fruity odors while significantly increasing undesirable aromas including beany, acidic, cooked-beans and spoiled odors. The spoiled odors increased with increasing acidity and heating temperatures. The strongest spoiled odor was observed in fermented soymilk at titratable acidity of 5.4 g/kg, sterilized at 90 °C. Apart from common volatiles that were inherent in soymilk and generated from lactic fermentation, 2-methyltetrahydrothiophen-3-one was found for the first time in soybean foods and was found to cause the spoiled odor. 44 volatiles found in thermally sterilized fermented soymilk were jointly formed its flavor wheel. This study provides important theoretical support for solving the problem of spoiled odor restricting the popularization of plant-based fermented soymilk.

Influence of ultra-high barrier packaging on the shelf-life of microwave-assisted thermally sterilized chicken pasta

This accelerated shelf life study of a ready-to-eat meal processed with a microwave-assisted thermal sterilization (MATS) system aimed to evaluate the performance of double metal oxide coated polyethylene terephthalate (PET) layers-based ultra-high barrier packaging along with ethylene vinyl alcohol (EVOH)-based pouches, and aluminum (AL) foil-based pouches (served as control). First, we evaluated barrier changes in the two types of pouches (double-layered PET and EVOH) caused by MATS processing. Next, we determined the influence of barrier properties on the physical, chemical and sensory quality of MATS-processed chicken pasta meals at accelerated storage conditions at 49 °C. Sensory evaluation was also done at lower storage temperature of 38 °C. Results demonstrated that MATS processing did not affect the barrier properties of double metal oxide coated PET pouches, however, it significantly influenced the barrier properties of EVOH-based pouches. After storage at 49 °C for 60 days, there was a small total color change (ΔE = 3.5) in chicken pasta meals in the double coated film pouches. This result was similar to that obtained for aluminum foil pouches (p > 0.05), but significantly lower than that for the EVOH pouches (ΔE = 5.5). The double metal oxide coated PET packaging provided an excellent barrier against lipid oxidation similar to that of aluminum (AL) foil-based pouches. A trained sensory panel scored the recipe between 6.0 and 6.45 immediately after MATS processing on a labelled effective magnitude (LAM) scale from 1 to 9 (worst to best quality). Results indicate that the newly developed double-layered PET pouches offer an excellent alternative to higher density metal foil-based packaging.

Characterization of Processing Influences on In Vitro Bioaccessibility of Carotenoids and Chlorophylls from Six Spinach Genotypes

Abstract Objectives Spinach is a rich source of bioactives including carotenoids and chlorophylls. Ultimate delivery, or bioavailability, of these bioactives to consumers varies depending on pre-/post-harvest factors that impact the food matrix. The interaction between food processing, oral processing (mastication), and spinach genotype have not been explored. Insights into these factors hold the potential to identify interaction effects between genotype and processing (GxP). Methods Six genotypes of spinach selected based on previous bioaccessibility screening were greenhouse grown in Salisbury, NC (Fall 2019), harvested, and stored fresh at 4C (24 hr) or at −80C after processing by blanching (2 min, 100C), thermal sterilization (121C for 15 min), or juicing. All genotypes were subjected to all processing methods, and a portion of each sample was subjected to simulated mastication while another was homogenized (30 sec) into a puree. All samples were subjected to a three-phase in vitro digestion to assess the transfer of carotenoids and chlorophyll derivatives from the food matrix to the aqueous micellar fraction (bioaccessibility). Results Processing method, genotype, and GxP had a significant influence on total bioactive content (P &amp;lt; 0.01), relative bioaccessibility (P &amp;lt; 0.01), and bioaccessible content (P &amp;lt; 0.01). Average bioactive content decreased in the order of juiced (26.2–36.9 μmol/g), blanched (23.3–30.0 μmol/g), thermally sterilized (22.5–27.3 μmol/g), and fresh spinach (18.6–25.0 μmol/g). Bioaccessible content decreased from juiced (6.8–9.8 μmol/g), to fresh (4.0–6.9 μmol/g) and blanched (4.6–5.6 μmol/g), and then thermally sterilized (2.4–3.3 μmol/g). Bioaccessible content from masticated samples was similar for thermally sterilized (0.9–1.5 μmol/g) and fresh samples (0.7–1.3 μmol/g). Conclusions Results indicate that heat treatment preserves bioactives in these six spinach genotypes and may modestly decrease their bioaccessibility. Influence of mastication on bioaccessible content of bioactives supports the notion that oral processing is a critical factor impacting ultimate bioaccessibility from vegetables. Together, these results provide valuable information for optimization of bioactive delivery. Funding Sources Foundation for Food and Agriculture Research.

Functionality of ultra-high barrier metal oxide-coated polymer films for in-package, thermally sterilized food products

Abstract Defects in metal oxide (MO)-coated polymer films increase their oxygen and water vapor transmission rates (OTRs, WVTRs), lowering the shelf-life of packaged food. In this study, we investigated the effects of thermal processing on six multilayered MO-coated films: MO-A (MO-coated PET(12 μm)//Oriented-Nylon 6 (15 μm)//Cast-Polypropylene (50 μm)), MO-B (SiOx-coated PET(12 μm)//Oriented-Nylon 6 (15 μm)//Cast-Polypropylene (60 μm)), MO-C (Overlayer/AlOx-organic-coated PET(13 μm)//Oriented-Nylon 6 (15 μm)//Cast-Polypropylene (50 μm)), MO-D (Overlayer/SiOx-coated PET(12 μm)//Oriented-Nylon 6 (15 μm)//Cast-Polypropylene (60 μm)), MO-E (AlOx-coated PET(12 μm)//AlOx-coated PET(12 μm)//Oriented-Nylon 6 (15 μm)//Cast-Polypropylene (70 μm)) and MO-F (AlOx-coated PET(12 μm)//AlOx-coated PET(12 μm)//AlOx-coated PET(12 μm)//Oriented-Nylon 6 (15 μm)//Cast-Polypropylene (70 μm)). Water filled film pouches were processed with a pilot-scale retort (30 and 40 min at 121 °C; F0 = 6–9 min) and microwave-assisted thermal sterilization unit (25-kW, single-mode, 915 MHz MATS system; F0 = 10.9 min). Subsequently, the pouches were emptied, filled with a color-changing oxygen sensor and stored at 23 ± 2 °C for 180-days. MO-F with three AlOx-coated PET layers, showed no oxygen permeation before and after retort and MATS processes. Compared to other films, MO-F exhibited low WVTRs after processing. Oxygen sensor in MO-F changed color at limited locations, indicating fewer defects. Confocal laser scanning microscope and scanning electron microscope images also showed less deterioration in MO-F. The dielectric loss factor (er) for MO-F was significantly less than other films (P

Color, vitamin C, β-carotene and sensory quality retention in microwave-assisted thermally sterilized sweet potato puree: Effects of polymeric package gas barrier during storage

In this study, we investigated the effects of package barrier properties on shelf-life of vitamin C-fortified sweet potato puree (SPP) processed with microwave-assisted thermal sterilization (MATS). Results show a change in SPP color during both processing and storage. The vitamin C in SPP decreased from 201.7 ± 4.7 to 185.8 ± 15.6 mg/100g during MATS and further decreased to as low as 13.6 ± 4.1 and 10.0 ± 0.3 mg/100g the end of 9 or 18 month, depending on the oxygen barrier and temperature. The total β-carotene content after processing and storage was slightly higher than before processing. Pouches with oxygen transmission rates (OTRs) of less than 0.3 cc/m2⋅day showed higher retention of color, vitamin C, and predicted shelf life than other pouches. However, this did not affect the consumer acceptance. Most panelists considered MATS processed SPP as a desirable baby food throughout the 18 months. Efforts are still needed to stabilize vitamin C content for over 3 years for military and NASA missions.

Free radical formation in chloramphenicol heated at different temperatures and the best thermal sterilization conditions – application of EPR spectroscopy and UV spectrophotometry

Free radicals in thermally treated chloramphenicol were examined by electron paramagnetic resonance (EPR) spectroscopy. The parameters and shape of EPR spectra were analysed and free radical concentrations were obtained in the tested drug samples. Chloramphenicol was thermally sterilized at pharmacopeia conditions: 100 °C (120 min). Sterilization was also carried out at different conditions, 110 °C (60 min) and 120 °C (30 min), for comparison with pharmacopeia settings. Microbiological analysis was performed on the samples to confirm sterility. The aim of this work was to determine the concentration of free radicals in chloramphenicol following thermal sterilization at pharmacopeia conditions and compare this with other sets of conditions [110 °C (60 min) and 120 °C (30 min)]. The best conditions of thermal sterilization are determined as those that kill microorganisms and produce the lowest amounts of free radicals in this drug. It was concluded that the optimal temperatures and times for the thermal sterilization of chloramphenicol are 100 °C and 120 min and 110 °C and 60 min. A temperature of 120 °C coupled with a heating time of 30 min was rejected for thermal sterilization because of the high amount of free radicals produced by the drug samples.

Application of EPR spectroscopy to examine free radicals evolution during storage of the thermally sterilized Ungentum ophthalmicum

Free radicals formed during thermal sterilization of the Ungentum ophthalmicum were examined by an X-band EPR spectroscopy. The influence of storage time (15 min; 1, 2 and 3 days after heating) on free radical properties and concentrations in this sample was determined. Thermal sterilization was done according to the pharmaceutical norms. The first-derivative EPR spectra with g-values about 2 were measured with magnetic modulation of 100 kHz in the range of microwave power 2.2–70 mW. The changes of amplitudes (A) and linewidths (ΔBpp) with microwave powers were evaluated. Free radicals in concentration ∼1017 spin/g were formed during heating of the tested Ungentum. Free radical concentration decreased with increase in storage time, and reached values ∼1017 spin/g after 3 days from sterilization. The tested U. ophthalmicum should not be sterilized at a temperature of 160 °C because of the free radicals formation, or it should be used 3 days after heating, when free radicals were considerably quenched. Free radical properties remain unchanged during storage of the Ungentum. The EPR lines of the U. ophthalmicum were homogeneously broadened and their linewidths (ΔBpp) increased with increase in microwave power. EPR spectroscopy is useful to examine free radicals to optimize sterilization process and storage conditions of ophthalmologic samples.

EPR examination of free radicals thermally formed in vaselinum flavum

Abstract The popular pharmaceutical base used in pharmacy – vaselinum flavum – was studied by an X-band (9.3 GHz) EPR spectrometer in the range of microwave power of 2.2–70 mW. The samples were sterilized in hot air oven at temperatures: 160°C (120 min), 170°C (60 min), and 180°C (30 min). The aim of this work was to determine properties and free radical concentrations in vaselinum flavum thermally sterilized at different conditions. The changes in free radical system in vaselinum flavum during storage were analyzed. Free radicals were found in all the heated samples. The lowest free radical concentration was obtained for vaselinum flavum heated at 180°C for 30 min; so these parameters are proposed for the thermal sterilization of this pharmaceutical base. Interactions with oxygen decreased free radical concentration in vaselinum flavum during storage. Strong quenching of free radicals in vaselinum flavum was observed after 2 days for the samples sterilized at temperatures 160 and 180°C. Such an effect for vaselinum flavum heated at temperature 170°C was observed later, 13 days after sterilization. Fast spin-lattice relaxation processes exist in thermally sterilized vaselinum flavum. The EPR lines of heated vaselinum flavum were homogeneously broadened. EPR spectroscopy and its use for examining the thermal sterilization process in pharmacy was confirmed.

Effect of microwave power on EPR spectra of thermally sterilized eucerinum anhydricum

Abstract Free radicals formed during thermal sterilization of eucerinum anhydricum – the pharmaceutical base were examined by an X-band (9.3 GHz) spectrometer. Eucerinum anhydricum was sterilized at different physical conditions according to the Polish Pharmacopeia norms. The samples were heated at temperatures: 160°C (120 min), 170°C (60 min), and 180°C (30 min). The aim of this study is to compare free radical concentration and effect of microwave power on EPR spectra of eucerinum anhydricum base thermally sterilized at different temperatures and periods of time. The effect of time storage on the free radicals in the heated samples was tested. Free radical concentrations in the sample stored 15 min strongly decreased with the increasing of sterilization temperature, probably as the result of recombination. Storage caused strong decrease of free radical concentrations in the samples, probably as the result of interactions with oxygen. It was observed to be independent of sterilization conditions from 2 days of storage and longer. Because of the lowest free radical concentration, for eucerinum anhydricum thermal sterilization at 180°C for 30 min is recommended. The sterilized samples should be stored at inert atmosphere without oxygen molecules. Fast spin-lattice relaxation processes existed in sterilized eucerinum anhydricum. The character of changes of amplitudes and linewidths of EPR lines with increasing of microwave power was the same for different storage times. The parameters of thermal sterilization and storage time influenced free radical concentration in eucerinum anhydricum, but magnetic spin-lattice interactions were unchanged. The usefulness of EPR spectroscopy in optimization of thermal sterilization process of eucerinum anhydricum was confirmed.

Electron paramagnetic resonance study of thermally treated bismuth subgallate.

Complex of bismuth, an anti-inflammatory drug, was studied by EPR spectroscopy. The aim of this study was to determine concentrations and properties of free radicals formed during thermal sterilization of bismuth subgallate according to pharmacopoeia norms to optimize its sterilization process. Different temperatures (160°C, 170°C, and 180°C) and times (120 minutes, 60 minutes, and 30 minutes) of sterilization were used. Interactions of bismuth subgallate with DPPH, the model free radical reference, were checked. g-Factors, amplitudes (A), integral intensities (I), and linewidths (ΔB pp) were obtained. Integral intensities were obtained by double integration of the first-derivative EPR lines. The influence of microwave power in the range of 2.2–70 mW on shape and parameters of the EPR spectra was examined. Thermal sterilization produced free radicals in bismuth subgallate in all tested cases. Strong interactions with free radicals were pointed out for all the analysed samples containing bismuth independent of sterilization conditions. Optimal conditions of thermal sterilization for bismuth subgallate with the lowest free radical formation are temperature 170°C and time of heating 60 minutes. Strong dipolar interactions exist in thermally sterilized bismuth subgallate. EPR spectroscopy is a useful method of examination of thermal sterilization conditions.

Effect of UV Irradiation and Temperature on Free Radical Properties in Dehydrocholic and Ursodeoxycholic Acids: An EPR Study

The effect of UV irradiation and temperature on the formation and properties of free radicals in two pharmaceutical important bile acids, such as dehydrocholic (DH) and ursodeoxycholic acids (UDC), was examined. Electron paramagnetic resonance (EPR) spectroscopy was applied to determine the paramagnetic character of UV irradiated and thermally sterilized drugs. Thermal and UV irradiation sterilizations of both compounds were carried out at different conditions according to pharmaceutical norms. The performed EPR measurements of UV irradiated and thermally sterilized DH and UDC samples proved the existence of the complex free radical systems in examined bile acids. Significant influence of UV irradiation in comparison with applied thermal sterilization on free radical concentrations in DH and UDC samples was observed. The results pointed out that thermal method is most suitable for bile acid sterilization. Therefore, this kind of sterilization should be applied in practice.

Comparing the impact of high pressure high temperature and thermal sterilization on the volatile fingerprint of onion, potato, pumpkin and red beet

This work reports the effect of high pressure high temperature (HPHT) processing as compared to thermal processing on the volatile fraction of four, industrially-relevant, vegetables: onion, potato, pumpkin and red beet. The vegetables were selected from different botanical families, edible plant parts and color groups, aiming for investigation of a wide range of chemical reactions. Despite the difference in chemical composition among these vegetables, some remarkable general trends could be found. Firstly, in all vegetables, Strecker degradation products (such as 2- and 3-methylbutanal) were detected at higher levels after HPHT sterilization in comparison to thermally sterilized counterparts. Secondly, HPHT sterilization enhanced oxidative degradation reactions (e.g. unsaturated fatty acids (in pumpkin, red beet and onion) and carotenoids (in pumpkin)). This work demonstrated the power of the untargeted multi-variate fingerprinting approach as a fast screening tool to zoom into relevant reaction pathways out of a complex network of chemical changes and to determine discriminative volatiles which can serve as potential markers.

Application of EPR Spectroscopy to Examination of Free Radical Formation in Thermally Sterilized Flumetasone.

Thermal formation of free radicals in flumetasone sterilized according to the pharmaceutical norms at 160, 170 and 180 °C was examined by electron paramagnetic resonance (EPR) spectroscopy. The microbiological analysis was done. Similar free radical concentrations were measured for flumetasone sterilized at 160 and 170 °C. The concentration was considerably higher than that for flumetasone sterilized at 180 °C. Fast spin–lattice relaxation processes, homogeneously broadened EPR lines, and complex free radicals system characterize the heated flumetasone. Free radicals were not observed 30 days after thermal sterilization. Optimal temperatures of sterilization of flumetasone are 160 and 170 °C.

Application of EPR Spectroscopy for Examination of Free Radical Formation in Thermally Sterilized Betamethasone, Clobetasol, and Dexamethasone

Paramagnetic centers in the three glucocorticosteroid drugs, such as betamethasone, clobetasol, and dexamethasone, were examined by the use of X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. Glucocorticosteroid drugs were sterilized according to the norms at 160 °C (120 min), 170 °C (60 min), and 180 °C (30 min). Free radical properties, types, and concentrations in the individual glucocorticosteroids were compared. The lineshape and parameters of EPR curves recorded in the range of the microwave power of 0.7–70 mW were tested. The non-heated drugs were diamagnetic. Free radicals were formed in clobetasol and dexamethasone drugs during process of their thermal sterilization, while free radicals were not detected in thermally sterilized betamethasone. Fast spin–lattice relaxation processes existed in heated clobetasol and dexamethasone. Their EPR lines were homogeneously broadened. A complex free radical system characterized these two drugs. Optimal conditions of sterilization of glucocorticosteroids were obtained. Betamethasone may be sterilized at 160, 170, and 180 °C. Clobetasol may be sterilized at 160 and 170 °C. Dexamethasone may be sterilized at 170 and 180 °C.

Shelf-Stable Egg-Based Products Processed by High Pressure Thermal Sterilization

Producing a thermally sterilized egg-based product with increased shelf life without losing the sensory and nutritional properties of the freshly prepared product is challenging. Until recently, all commercial shelf-stable egg-based products were sterilized using conventional thermal processing; however, this heat treatment was problematic as quality attributes of the product were negatively affected. Combining high pressure with high temperature is a potential alternative to retorting for the production of shelf-stable egg-based products. This review discusses the challenges of high pressure thermal sterilization as an alternative processing method of producing shelf-stable egg products. Attention is given to product improvement in terms of overall quality through modification of ingredients, formulation, processing and packaging, offering the industry a practical way to produce egg-based products with increased shelf life and appealing quality to the consumer.

Free Radicals in the Thermally Sterilized Aminoglycoside Antibiotics

Changes of the chemical structure and free radicals formation in aminoglycoside antibiotics during sterilization at temperatures 160°C, 170°C, and 180°C according to the pharmacological norms were studied. EPR and DRIFT spectroscopy were applied as experimental methods. It was demonstrated that free radicals are formed in streptomycin, gentamicin, neomycin, sisomicin, paromomycin, and tobramycin during thermal sterilization. Complex free radicals system with the complex shape of EPR spectra characterized the tested samples. Mainly oxygen free radicals exist in the tested heated antibiotics. The EPR lines of the analyzed antibiotics are homogeneously broadened. Fast spin-lattice relaxation processes exist in the examined sterilized aminoglycoside antibiotics. Free radicals concentrations in the aminoglycoside antibiotics depend on the temperature and time of sterilization. The highest free radicals concentrations characterize thermally sterilized sisomicin. Streptomycin, gentamicin, neomycin, paromomycin, and tobramycin may be sterilized at temperatures 160°C, 170°C and 180°C. Sisomicin should be sterilized at temperature 180°C. Free radicals concentration changes during storage of the examined antibiotics, and probably interactions with oxygen molecules may be responsible for this effect. DRIFT studies shown that sterilization conditions, the temperature and the presence of oxygen, causes only small changes in the chemical structure of aminoglycoside antibiotics by alteration of the functional groups. EPR and DRIFT methods are proposed to optimization of the thermal sterilization process of drugs and conditions of their storage.

FIRMNESS OF THERMAL PROCESSED ONION AS AFFECTED BY BLANCHING

The pectin methyl esterase enzyme system was shown to be involved in firmness of thermally treated onion in the temperature range 50–70C. Thermal softening of onion at 90 and 100C showed an initial steep negative slope with a shallow negative slope at longer heating time. Low-temperature blanching at 70C was effective to maintain firm onion tissue exposed to excessive heating. Physical strength of onion was substantially diminished when exposed to a commercial sterilization condition where F0, extent of thermal sterilization, was 3, and/or more. Blanching in water for 120 min at 70C resulted in a maximum value for the firmness of commercially sterilized onion. Firmness of onion, blanched in calcium brine at a concentration range of 0.0–1.0% (wt) prior to heat treatment, decreased with increasing severity of thermal sterilization treatment. At F0 = 6, blanching in 0.5% calcium brine resulted in maximum firmness of thermally sterilized onion, approximately 70% of that of raw onion.