Effects of High‐Hydrostatic Pressure on Inactivation of Human Norovirus and Physical and Sensory Characteristics of Oysters

The purpose of the study was to determine the effect of high‐hydrostatic pressure (HHP) on inactivation of human norovirus (HuNoV) in oysters and to evaluate organoleptic characteristics of oysters treated at pressure levels required for HuNoV inactivation. Genogroup I.1 (GI.1) or Genogroup II.4 (GII.4) HuNoV was inoculated into oysters and treated at 300 to 600 MPa at 25 and 0 °C for 2 min. After HHP, viral particles were extracted by porcine gastric mucin‐conjugated magnetic beads (PGM‐MBs) and viral RNA was quantified by real‐time RT‐PCR. Lower initial temperature (0 °C) significantly enhanced HHP inactivation of HuNoV compared to ambient temperature (25 °C; P < 0.05). HHP at 350 and 500 MPa at 0 °C could achieve more than 4 log₁₀ reduction of GII.4 and GI.1 HuNoV in oysters, respectively. HHP treatments did not significantly change color or texture of oyster tissue. A 1‐ to 5‐scale hedonic sensory evaluation on appearance, aroma, color, and overall acceptability showed that pressure‐treated oysters received significantly higher quality scores than the untreated control (P < 0.05). Elevated pressure levels at 450 and 500 MPa did not significantly affect scores compared to 300 MPa at 0 °C, indicating increasing pressure level did not affect sensory acceptability of oysters. Oysters treated at 0 °C had slightly lower acceptability than the group treated at room temperature on day 1 (P < 0.05), but after 1 wk storage, no significant difference in sensory attributes and consumer desirability was observed (P > 0.05).     

超高压处理对冷藏鲍鱼保鲜效果与品质变化的影响

本文以鲍鱼为材料,研究了超高压处理对鲍鱼体内微生物的消减作用和不同压力超高压处理后的鲍鱼在冷藏过程中挥发性盐基氮值、p H、脂肪氧化值、肌肉组织与硬度的变化情况,对比了热加工和超高压处理对鲍鱼品质变化的影响。研究结果显示,超高压具有良好的杀菌效果,鲍鱼经400 MPa和500 MPa处理10 min,体内菌落总数达到未检出状态,贮藏20 d后,仍符合生食标准。超高压处理能有效抑制鲍鱼挥发性盐基氮的产生,在4℃条件下保存30 d后TVB-N值仍小于35 mg/100 g。经超高压处理后的鲍鱼p H显著高于未加工鲍鱼,但4℃贮藏30 d后,超高压处理后的鲍鱼p H反而显著低于未加工鲍鱼;相比热加工和未加工的对照条件,超高压处理能延迟TBA值的升高,抑制脂肪氧化;组织切片和质构实验发现经超高压处理的鲍鱼肌肉纤维凝聚,肉质硬度升高,但随着贮藏时间的延长,硬度逐渐下降。结果表明,鲍鱼经400 MPa压力处理10 min,冷藏20 d后仍可生食,同时品质得到良好的提升。      

A Gompertz Model Approach to Microbial Inactivation Kinetics by High‐Pressure Processing (HPP): Model Selection and Experimental Validation

A recently proposed Gompertz model (GMPZ) approach describing microbial inactivation kinetics by high‐pressure processing (HPP) incorporated the initial microbial load (N₀) and lower microbial quantification limit (N_lim), and simplified the dynamic effects of come‐up time (CUT). The inactivation of Listeria innocua in milk by HPP treatments at 300, 400, 500, and 600 MPa and pressure holding times (t_hold) ≤10 min was determined experimentally to validate this model approach. Models based on exponential, logistic‐exponential, and inverse functions were evaluated to describe the effect of pressure on the lag time (λ) and maximum inactivation rate (μ_max), whereas the asymptote difference (A) was fixed as A = log₁₀(N₀/N_lim). Model performance was statistically evaluated and further validated with additional data obtained at 450 and 550 MPa. All GMPZ models adequately fitted L. innocua data according to the coefficient of determination (R² ≥ 0.95) but those including a logistic‐exponential function for μ_max(P) were superior (R² ≥ 0.97). These GMPZ versions predicted that approximately 597 MPa is the theoretical pressure level (P_λ) at which microbial inactivation begins during CUT, mathematically defined as λ (P = P_λ) = t_CUT, and matching the value observed on the microbial survival curve at 600 MPa. As pressure increased, predictions tended to slightly underestimate the HPP lethality in the tail section of the survival curve. This may be overseen in practice since the observed microbial counts were below the predicted log₁₀ N values. Overall, the modeling approach is promising, justifying further validation work for other microorganisms and food systems.     

Design of an Optimum Computer Vision‐Based Automatic Abalone (Haliotis discus hannai) Grading Algorithm

An automatic abalone grading algorithm that estimates abalone weights on the basis of computer vision using 2D images is developed and tested. The algorithm overcomes the problems experienced by conventional abalone grading methods that utilize manual sorting and mechanical automatic grading. To design an optimal algorithm, a regression formula and R² value were investigated by performing a regression analysis for each of total length, body width, thickness, view area, and actual volume against abalone weights. The R² value between the actual volume and abalone weight was 0.999, showing a relatively high correlation. As a result, to easily estimate the actual volumes of abalones based on computer vision, the volumes were calculated under the assumption that abalone shapes are half‐oblate ellipsoids, and a regression formula was derived to estimate the volumes of abalones through linear regression analysis between the calculated and actual volumes. The final automatic abalone grading algorithm is designed using the abalone volume estimation regression formula derived from test results, and the actual volumes and abalone weights regression formula. In the range of abalones weighting from 16.51 to 128.01 g, the results of evaluation of the performance of algorithm via cross‐validation indicate root mean square and worst‐case prediction errors of are 2.8 and ±8 g, respectively.     

Effects of High‐Pressure Processing on Inactivation of Salmonella Typhimurium,Eating Quality,and Microstructure of Raw Chicken Breast Fillets

Abstract: High‐pressure inactivation of Salmonella Typhimurium DMST 28913, eating quality, and microstructure of pressurized raw chicken breast meat was determined. The inoculated samples (approximately 7 log CFU/g initial load) were processed at 300 and 400 MPa, using pressurized medium of 25 to 35 °C during pressurization. Weibull model was well fitted to the survival curves with tailing. Least severe conditions with acceptable inactivation levels were 300 MPa, 35 °C, 1 min (approximately 2 log reduction) and 400 MPa, 30 °C, 1 min (approximately 4 log reduction). Based on these 2 conditions, the 400 MPa treatment yielded the raw chicken meat with higher L* value, greater cooking loss, and lower water holding capacity. Cooked chicken breast meat prepared from the pressurized samples had firmer texture than the control. Scanning electron microscopic images showed that higher pressure resulted in increasing extent of protein coagulation and the contraction of the muscle bundles. Practical Application: For raw chicken breast fillet, 300 MPa, 35 °C, 1 min was the condition that reasonably reduced the load of Salmonella Typhimurium. However, the pressurized samples had greater cooking loss. Marination with brine containing sodium chloride and phosphate prior to pressurization might help improve this eating quality.     

Comparing the Effects of Ultra‐High‐Pressure Homogenization and Conventional Thermal Treatments on the Microbiological,Physical, and Chemical Quality of Almond Beverages

The effects of ultra‐high‐pressure homogenization (UHPH) at 200 and 300 MPa, in combination with different inlet temperatures (55, 65, and 75 °C) on almond beverages with lecithin (AML) and without lecithin (AM), were studied. UHPH‐treated samples were compared with the base product (untreated), pasteurized (90 °C, 90 s), and ultra‐high‐temperature (UHT, 142 °C, 6 s) samples. Microbiological analysis, physical (dispersion stability, particle size distribution, and hydrophobicity), and chemical (hydroperoxide index) parameters of special relevance in almond beverages were studied. Microbiological results showed that pressure and inlet temperature combination had a significant impact on the lethal effect of UHPH treatment. While most UHPH treatments applied produced a higher quality of almond beverage than the pasteurized samples, the combination of 300 MPa and 65 and/or 75 °C corresponded to a maximum temperature after high pressure valve of 127.7 ± 9.7 and 129.3 ± 12.6 °C, respectively. This temperature acted during less than 0.7 s and produced no bacterial growth in almond beverages after incubation at 30 °C for 20 d. UHPH treatments of AML samples caused a significant decrease in particle size, resulting in a high physical stability of products compared to conventional heat treatments. UHPH treatment produced higher values of hydroperoxide index at day 1 of production than heat‐treated almond beverage. Hydrophobicity increased in AML‐UHPH‐treated samples compared to AM and conventional treatments. Practical Application: Ultra‐high‐pressure‐homogenization (UHPH) is an emerging technology, a potential alternative to conventional heat treatments. It is a simple process consisting of single step. When liquid food (almond beverage in this study) passes through the high‐pressure valve, a very good stability and reduction of microorganisms is achieved, both effects due to the particle breakdown. Specific UHPH conditions could produce commercial sterilization of almond beverage.     

High‐Pressure Inactivation of Enzymes: A Review on Its Recent Applications on Fruit Purees and Juices

In the last 2 decades high‐pressure processing (HPP) has established itself as one of the most suitable nonthermal technologies applied to fruit products for the extension of shelf‐life. Several oxidative and pectic enzymes are responsible for deterioration in color, flavor, and texture in fruit purees and juices (FP&J). The effect of HPP on the activities of polyphenoloxidase, peroxidase, β‐glucosidase, pectinmethylesterase, polygalacturonase, lipoxygenase, amylase, and hydroperoxide lyase specific to FP&J have been studied by several researchers. In most of the cases, partial inactivation of the target enzymes was possible under the experimental domain, although their pressure sensitivity largely depended on the origin and their microenvironmental condition. The variable sensitivity of different enzymes also reflects on their kinetics. Several empirical models have been established to describe the kinetics of an enzyme specific to a FP&J. The scientific literature in the last decade illustrating the effects of HPP on enzymes in FP&J, enzymatic action on those products, mechanism of enzyme inactivation during high pressure, their inactivation kinetics, and several intrinsic and extrinsic factors influencing the efficacy of HPP is critically reviewed in this article. In addition, process optimization of HPP targeting specific enzymes is of great interest from an industrial approach. This review will give a fair idea about the target enzymes specific to FP&J and the optimum conditions needed to achieve sufficient inactivation during HPP treatment.     

超高压处理对牛肉主要理化品质的影响

探讨超高压处理(不同压力和保压时间)对牛肉主要理化品质的影响。牛半腱肌肉经200～600MPa压力分别处理10min和20min,分析胶原蛋白含量和溶解性等特性以及牛肉蒸煮损失和嫩度在超高压处理过程中的变化。结果表明：随着压力的升高,牛半腱肌肉的剪切力均呈下降趋势,保压时间为20min时剪切力下降更显著。当压力达600MPa,牛肉剪切力分别降至39.59N(保压10min)和31.36N(保压20min)。总胶原蛋白、可溶性胶原蛋白的含量和胶原蛋白的溶解性随着处理压力的升高而增加。胶原蛋白特性变化与肉品质之间存在显著相关性。     

Continuous Versus Discontinuous Ultra‐High‐Pressure Systems for Food Sterilization with Focus on Ultra‐High‐Pressure Homogenization and High‐Pressure Thermal Sterilization: A Review

High‐pressure thermal sterilization (HPTS) and ultra‐high‐pressure homogenization (UHPH) are two emerging sterilization techniques that have not been implemented in the food industry yet. The two technologies apply different acting principles as HPTS uses isostatic pressure in combination with heat whereas UHPH uses dynamic pressure in combination with shear stress, cavitation, impingement, and heat. Both technologies offer significant benefits in terms of spore inactivation in food production with reduced thermal intensity and minimized effects on sensory and nutritional profiles. These benefits have resulted in relevant research efforts on both technologies over the past few decades. This state of the art of the discontinuous HPTS‐based and the continuous UHPH‐based sterilization concepts are assessed within this review. Further, various basic principles and promising future preservation applications of HPTS and UHPH for food processing, that are also applicable in the pharmaceutical, biochemical, and biotechnological sectors, are summarized. In addition, the applications and limitations of these technologies in terms of optimizations needed to overcome the identified challenges are emphasized.     

Tauropine and D-Lactate as Metabolic Stress Indicators during Transport and Storage of Live Paua, (New Zealand Abalone) (Haliotis iris)

Pyruvate reductase end products were evaluated as specific indicators of anaerobic stress in the New Zealand paua (Haliotis iris). The foot and shell adductor muscles contained D-lactate and tauropine dehydrogenases: the latter was isolated for the enzymatic determination of tauropine in muscle extracts. Enforced exercise and prolonged exposure to air led to accumulation of tauropine, and to a lesser extent D-lactate, in the foot and adductor. Exercise decreased the glycogen content of both muscles and adenylate energy change in the adductor. Monitoring tauropine and D-lactate should prove useful for quality control of live abalone during culture, transport and storage.     

The Effect of Stunning Methods on Rigor Mortis and Texture Properties of Atlantic Salmon (Salmo Salar)

Shear force and rigor mortis were used to evaluate the post‐mortem changes of muscle texture in Atlantic salmon (Salmo salar). The fish were either stunned with carbon dioxide (CO₂), electricity, or percussion prior to slaughter. The pre‐mortem stress during CO₂ stunning resulted in an earlier onset and resolution of rigor mortis, and accelerated post‐mortem softening of the muscle tissue as compared to the other stunning methods. No significant differences, either in development of rigor mortis or shear force, were seen between fish that were stunned with electricity or by percussion. Consequently electricity can be used for stunning fish prior to slaughter.     

Effect of temperature–time pretreatments on the texture and microstructure of abalone (Haliotis discus hanai)

The effects of temperature/time pretreatments on the texture and microstructure of abalone (Haliotis discus hanai ) meat with the same myofibril extraction rate (60–66.7%) were investigated. The abalone samples were categorized into control and four treatment groups of different heating temperature/heating time combinations as 50°C/120 min, 60°C/10 min, 70°C/5 min, and 80°C/2 min, respectively. Compared to the control samples, the abalone samples heated at 60°C/10 min were the most tender (minimum shear force). It is clear that a sharp reduction in hardness was observed in heat treated abalone meat samples, compared to the raw samples. Nuclear magnetic resonance (NMR) showed that the water distribution pattern in abalone samples changed as they were experiencing different heat treatments. Particularly, the immobilized water components in samples heated at 60°C/10 min increased significantly. The textural properties of these samples evaluated after an 80 s‐reheating by microwave were of superior quality. It is concluded that the optimal condition for pretreatment abalone was 60°C/10 min, which could significantly improve the textural properties of preprocessed abalones.

Practical applications

Ready‐to‐eat foods can either be consumed directly, or further prepared according to consumers' preference. They are processed and packed following scientifically defined criteria to meet ready‐to‐eat requirements. For consumers, the quality of the food is one of the most important factors affecting purchasing decisions. Pretreatment through heating plays a key role in determining the eating quality of the product. Our study investigated the effects of pretreatment temperature and time on the food quality. These findings will establish optimal conditions for pretreating abalone to develop high‐quality ready‐to‐eat food products.

     

基于神经网络法优化即食皱纹盘鲍栅栏模式

以栅栏技术理论为指导,采用神经网络模型优化不同栅栏模式对即食鲍鱼（Haliotis discus hannai Ino）产品的防腐保鲜效果。通过研究几个栅栏因子（烘干后产品的水分活度（aw）、乳酸链球菌素（Nisin）、乳酸钠的添加量以及杀菌温度）组合得到的不同栅栏模式的防腐保鲜效果以及对产品品质的影响,以菌落总数及感官评分作为响应值建立神经网络模型并进行优化。结果表明：产品最适栅栏模式为：aw为0.92,Nisin、乳酸钠添加量分别为0.39 g/kg、1.6%,杀菌温度89 ℃,此栅栏模式防腐保鲜效果好,且能较好地保持产品的质地和风味。     

High‐pressure processing‐induced conformational changes during heating affect water holding capacity of myosin gel

This study aimed to investigate the effects of high‐pressure processing (HPP) (0.1‐400 MPa for 9 min) on the water holding capacity (WHC) of heat‐induced rabbit myosin gel and structural changes during thermal treatment (25–75 °C). HPP at 100 MPa significantly increased the WHC (P < 0.05) and formed more regular and homogeneous three‐dimensional network. Myosin tails at 100 MPa unfolded completely during the thermal treatment, which was beneficial to form a high WHC gel network. However, myosin pressurised at 200 MPa and above formed a weak gel. Their heads were already aggregated before heating, preventing from subsequent thermal denaturation and aggregation. With the temperature increasing, unfolding of myosin tails was not sufficient for a filamentous network formation. These results suggested that HPP could modify the myosin structure and affect the gel formation during heating. The 100 MPa was the optimum pressure level for the WHC of rabbit myosin gel.     

High‐Pressure Thermal Sterilization: Food Safety and Food Quality of Baby Food Puree

The benefits that high‐pressure thermal sterilization offers as an emerging technology could be used to produce a better overall food quality. Due to shorter dwell times and lower thermal load applied to the product in comparison to the thermal retorting, lower numbers and quantities of unwanted food processing contaminants (FPCs), for example, furan, acrylamide, HMF, and MCPD‐esters could be formed. Two spore strains were used to test the technique; Geobacillus stearothermophilus and Bacillus amyloliquefaciens, over the temperature range 90 to 121 °C at 600 MPa. The treatments were carried out in baby food puree and ACES‐buffer. The treatments at 90 and 105 °C showed that G. stearothermophilus is more pressure‐sensitive than B. amyloliquefaciens. The formation of FPCs was monitored during the sterilization process and compared to the amounts found in retorted samples of the same food. The amounts of furan could be reduced between 81% to 96% in comparison to retorting for the tested temperature pressure combination even at sterilization conditions of F₀‐value in 7 min.     

佛跳墙主料中鲍鱼预处理方法的加工工艺优化

为使佛跳墙产品具有稳定的品质和较好的贮藏性能以便于工业化生产,对其加工工艺进行改进,采用罐头加工工艺取代原有的经验式烹饪做法,并对主料加工采用条件可控的预处理方法。以佛跳墙主料之一的鲍鱼为实验对象,分别研究不同水发时间、水发温度及预煮时间对其质构和感官的影响。以感官得分为主要实验指标,在单因素试验基础上,根据Box-Behnken试验设计原理,采用响应面法优化主料加工工艺,结果表明,鲍鱼的最优工艺组合为水发时间12.48 h、水发温度44.50 ℃、预煮时间16.1 min,此时具有最高的感官得分,经验证实验表明理论与实际基本相符。结合主料的质构分析,当主料质构指标分别在一定的范围时,具有较好的感官品质,可用于监控产品生产质量。     

Effects of Ultra High Pressure,Pressing Time and HCl Concentration on Non‐thermal Starch Hydrolysis Using Ultra High Pressure

Effects of ultra high pressure (UHP), pressing time and HCl concentration on non‐thermal starch hydrolysis using ultra high pressure were investigated. As regards ultra high pressure, starch granules maintained their structure up to 450 MPa and were partially disintegrated at 600 MPa. Degree of hydrolysis did not change up to 450 MPa and dramatically increased at 600 MPa indicating that starch hydrolysis increased with increasing destruction of starch granules. Pressing time did not affect the degree of hydrolysis. However, degree of hydrolysis and destruction of starch granules increased with increasing HCl concentration up to 4 M. Gel permeation chromatography showed that the soluble fraction of starch formed by hydrolysis mainly consisted of maltooligomers and maltose. X‐ray diffraction pattern changed from A type to C type upon hydrolysis, otherwise it remained as A type. This work provides fundamental information of UHP processing for starch and shows a potential of non‐thermal UHP processing for a new starch hydrolysis method.