Comparison of Microbial Inactivation and Rheological Characteristics of Mango Pulp after High Hydrostatic Pressure Treatment and High Temperature Short Time Treatment

Physical Stability of Chestnut Lily Beverages (CLB): Effects of Shear Homogenization on Beverage Rheological Behavior, Particle Size, and Sensory Properties

The processing parameters have a crucial influence on the stability and sensory quality of beverages. The focus of this study is to observe the rheological behavior, particle size distribution, stability, color change, and sensory evaluation of chestnut lily beverages (CLB) at different rotational speeds (0~20,000 rpm) using a high-shear homogeneous disperser. The CLB system exhibited non-Newtonian shear-thinning behavior. As the homogenization speed increased (0~12,000 rpm), the viscosity increased (0.002~0.059 Pa.s). However, when the rotational speed shear continued to increase (12,000~20,000 rpm), the viscosity decreased slightly (0.035~0.027 Pa.s). Under all homogeneous conditions, the turbidity and precipitation fractions were the lowest when the rotational speed was 12,000 rpm: the sedimentation index was lowest at this point (2.87%), and the relative turbidity value of CLB was largest at this point (80.29%). The average beverage particle diameter and ascorbic acid content showed a downward trend at the homogenization speed from 0 to 20,000 rpm, whereas the total soluble solids (TSS) content followed the opposite trend. The results show that these physical properties can be correlated with different rotational speeds of homogenization. This study explained the effect of homogenization speed on CLB properties, which needs to be considered in beverage processing, where high-speed shear homogenization can serve as a promising technique.

Non-volatile and volatile metabolic profiling of tomato juice processed by high-hydrostatic-pressure and high-temperature short-time

High hydrostatic pressure (HHP) processing has become a commercial success in fruit and vegetable processing. Herein, the effects of HHP and high-temperature short-time (HTST) processing on metabolic profiling in tomato juice was evaluated by UPLC-MS/MS, HPLC, and GC-MS; a total of 425 metabolites, 14 carotenoids, and 56 volatile compounds were identified in tomato juice. HHP processing affects the composition of the juice less than HTST processing, considering 4 and 33 differential metabolites discriminated after HHP and HTST processing, respectively. The total lycopene and carotenoid contents in tomato juice increased after HHP processing, while the β-carotene and lycopene contents decreased after HTST processing. Further, more volatile compounds and higher contents of aldehydes that contribute to green aroma and lower contents of alcohols were observed after HHP and HTST processing, respectively. These findings provide a comprehensive understanding of the advantages of HHP processing on metabolite profiles in tomato juice.

Effect of Different Sterilization Methods on the Microbial and Physicochemical Changes in Prunus mume Juice during Storage

This study evaluated the pasteurization (P), ozone (O3), ultrasonic (US), and high-hydrostatic-pressure (HHP) sterilization approaches for processing of Prunus mume regarding browning factors and microorganisms, compared with non-sterilization (control check, CK) treatment. The microorganisms (total bacterial count and fungi and yeast count) in the juice were identified after different sterilization techniques, while the quality parameter changes (degree of browning, color measurements, total phenolic content, reducing sugar, ascorbic acid, 5-hydroxymethyl furaldehyde (5-HMF), amino acid nitrogen, total soluble solids (TSS), pH value) were investigated. The results indicate that P and HHP treatment reduced non-enzymatic browning while substantially impacting the color measurements, TSS, and pH, while the sterilization effect was remarkable, with a rate exceeding 90%. Furthermore, the Prunus mume juices treated with P and HHP sterilization were used as the objects, and the CK group was used as the control group. They were placed at 4 °C, 25 °C and 37 °C, respectively, and stored in dark for 15 d. Sampling and determination were carried out on 0, 3, 6, 9, 12, and 15 d, respectively. M-&-Y (molds and yeasts) were not detected in the late storage period, and no obvious microbial growth was observed during storage, indicating that P and HHP treatments could ensure the microbial safety of Prunus mume juice. P- and HHP- treated Prunus mume juice has better quality and low temperature storage is beneficial for maintaining the quality of Prunus mume juice. Therefore, P treatment or HHP treatment combined with low temperature storage could achieve a more ideal storage effect. Overall, this study conclusively established that P and HHP methods were suitable for sterilizing Prunus mume juice. These techniques minimally affected overall product quality while better maintaining the quality parameters than the untreated juice samples and those exposed to O3 and US treatment.

A Novel Method of a High Pressure Processing Pre-Treatment on the Juice Yield and Quality of Persimmon

This study investigates the effects of a high pressure processing pre-treatment (pre-HPP) on the juice yield of persimmon (Diospyros kaki L.) pulp and the pre-HPP plus HPP or thermal processing (TP) on microorganism inactivation and quality changes of the persimmon juice. The “Gongcheng” persimmon was selected with the highest juice yield (48.9%), and the pre-HPP set at 300 MPa/8 min increased the juice yield by 60% through an increasing pectin methylesterase (PME) activity of 25.03% and by maintaining polygalacturonase (PG) activity. For different processing modes, namely, pre-HPP plus HPP at 550 Mpa/5 min and pre-HPP plus TP treatment at 95 °C/5 min, both of the guaranteed microorganisms in the juice were below 2.0 lg CFU/mL; however, the persimmon juice treated by the pre-HPP plus HPP had higher contents of total phenol and ascorbic acid which were 16.07 mg GAE/100 g and 17.92 mg/100 mL, respectively, a lower content of soluble tannin which was 55.64 μg/mL, better clarity which was 18.6% and less color change where the ΔE was only 2.68.

Factors Affecting Microbial Inactivation during High Pressure Processing in Juices and Beverages: A Review

ABSTRACT

The purpose of this article is to review and discuss the factors affecting high pressure processing (HPP) in juices and beverages. The inactivation of microorganisms by HPP depends on numerous factors, including the magnitude of the pressure and the holding time, process temperature, compression and decompression rates, the microbiota, and the intrinsic properties of juices and beverages. Although extensive HPP research has been performed to characterize many of these factors, a number of issues, such as the rates of compression and decompression, still remain unresolved and need further investigation. In addition, some published results are conflicting and do not provide enough evidence to develop juice HPP "safe-harbor" parameters to achieve a minimum 5-log reduction of the pertinent microorganism and produce safe fruit juices and beverages.

HIGHLIGHTS

Effects of High-Pressure Homogenization on the Structural, Physical, and Rheological Properties of Lily Pulp

The effects of high-pressure homogenization (HPH) on the structural, physical, and rheological properties of lily pulp (15%, w/w) were investigated. Different pressures ranging from 0 MPa to 100 MPa were used. The focus was on evaluating the changes in the particle size distribution (PSD), structure, pulp sedimentation behavior, serum cloudiness (SC), total soluble solids (TSS), color, and rheological behavior of the pulps. PSD analysis showed that the diameter of suspended lily particles significantly decreased with an increasing homogenization pressure. The suspended particles observed through optical microscopy became small after homogenization, highlighting the effect of HPH on disrupting the suspended particles. Compared with the untreated pulp, the SC and sedimentation velocity of the homogenized pulps decreased due to the disruption of the suspended particles. The effects of HPH on the sedimentation index and SC exhibited an asymptotic behavior similar to that of the changes in the particle size of lily pulp. Moreover, HPH processing reduced the viscosity of lily pulp and increased the TSS and lightness of the homogenized pulps. HPH significantly modified the structural, physical, and rheological properties of lily pulp. The pulp homogenized above 60 MPa had good suspension stability. This finding indicates that HPH technology can be used to improve the stability of lily pulp.

Evaluation of Different Dose-Response Models for High Hydrostatic Pressure Inactivation of Microorganisms

Modeling of microbial inactivation by high hydrostatic pressure (HHP) requires a plot of the log microbial count or survival ratio versus time data under a constant pressure and temperature. However, at low pressure and temperature values, very long holding times are needed to obtain measurable inactivation. Since the time has a significant effect on the cost of HHP processing it may be reasonable to fix the time at an appropriate value and quantify the inactivation with respect to pressure. Such a plot is called dose-response curve and it may be more beneficial than the traditional inactivation modeling since short holding times with different pressure values can be selected and used for the modeling of HHP inactivation. For this purpose, 49 dose-response curves (with at least 4 log10 reduction and ≥5 data points including the atmospheric pressure value (P = 0.1 MPa), and with holding time ≤10 min) for HHP inactivation of microorganisms obtained from published studies were fitted with four different models, namely the Discrete model, Shoulder model, Fermi equation, and Weibull model, and the pressure value needed for 5 log10 (P₅) inactivation was calculated for all the models above. The Shoulder model and Fermi equation produced exactly the same parameter and P₅ values, while the Discrete model produced similar or sometimes the exact same parameter values as the Fermi equation. The Weibull model produced the worst fit (had the lowest adjusted determination coefficient (R²adj) and highest mean square error (MSE) values), while the Fermi equation had the best fit (the highest R²adj and lowest MSE values). Parameters of the models and also P₅ values of each model can be useful for the further experimental design of HHP processing and also for the comparison of the pressure resistance of different microorganisms. Further experiments can be done to verify the P₅ values at given conditions. The procedure given in this study can also be extended for enzyme inactivation by HHP.