Nonthermal pasteurization of pineapple juice: A review on the potential of achieving microbial safety and enzymatic stability.

Pineapple juice is preferred by consumers for its unique aroma and flavor that come from a set of amino acids, amines, phenolic compounds, and furanone. The juice is susceptible to spoilage, and a common practice is to pasteurize it at 70-95°C for 0.5-5 min. However, the characteristic flavors and phytochemicals are negatively influenced by the intense time-temperature treatment. To retain the thermosensitive compounds in the juice, some nonthermal technologies such as high-pressure processing, pulsed electric field, pulsed light, ultrasound, and ultraviolet treatments have been explored. These techniques ensured microbial safety (5-log reduction in E. coli, S. Typhimurium, or S. cerevisiae) while preserving a maximum ascorbic acid (84-99%) in the juice. The shelf life of these nonthermally treated juice varied between 14 days (UV treated at 7.5 mJ/cm2 ) and 6 months (clarified through microfiltration). Moreover, the inactivation of spoilage enzyme in the juice required a higher intensity. The present review discusses the potential of several nonthermal techniques employed for the pasteurization of pineapple juice. The pasteurization ability of the combined hurdle between mild thermal and nonthermal processing is also presented. The review also summarizes the target for pasteurization, the plan to design a nonthermal processing intensity, and the consumer perspective toward nonthermally treated pineapple juice. The techniques are compared on the common ground like safety, stability, and quality of the juice. This will help readers to select an appropriate nonthermal technology for pineapple juice production and design the intensity required to satisfy the manufacturers, retailers, and consumers.

Pasteurization of fruit juices by pulsed light treatment: A review on the microbial safety, enzymatic stability, and kinetic approach to process design.

Pulsed light (PL) is a polychromatic radiation-based technology, among many other non-thermal processing techniques. The microbiological lethality of the PL technique has been explored in different food matrices along with their associated mechanisms. Pasteurization of fruit juice requires a 5-log cycle reduction in the resistant pathogen in the product. The manufacturers look toward achieving the microbial safety and stability of the juice, while consumers demand high-quality juice. Enzymatic spoilage in fruit juice is also a crucial factor that needs attention. The retailers want the processed juice to be stable, which can be achieved by inactivating the spoilage enzymes and native microflora inside it. The present review argued about the potential of PL technology to produce a microbiologically safe and enzymatically stable fruit juice with a minimal loss in bioactive compounds in the product. Concise information of factors affecting the PL treatment (PLT), primary inactivation mechanism associated with microorganisms, enzymes, the effect of PLT on various quality attributes (microorganisms, spoilage enzymes, bioactive components, sensory properties, color), and shelf life of fruit juices has been put forward. The potential of PL integrated with other non-thermal and mild thermal technologies on the microbial safety and stability of fruit juices has been corroborated. The review also provides suggestions to the readers for designing, modeling, and optimizing the PLT and discusses the use of various primary, secondary kinetic models in detail that have been utilized for different quality parameters in juices. Finally, the challenges and future need associated with PL technology has been summarized.

Partial purification, characterisation and thermal inactivation kinetics of peroxidase and polyphenol oxidase isolated from Kalipatti sapota (Manilkara zapota).

BACKGROUND: The extraction, purification, and characterisation of peroxidase (POD) and polyphenol oxidase (PPO) were studied for Kalipatti sapota fruit. The crude enzyme extract was partially purified by ammonium sulfate precipitation followed by BioGel P100 size exclusion and Unosphere Q anion-exchange chromatography. RESULTS: Molecular weights of 20 kDa (POD) and 24 kDa (PPO) were indicated by SDS-PAGE. A single band was observed on SDS-PAGE with a fold purity of 10.38 and 7.42 for POD and PPO, respectively. Michaelis-Menten constants for POD and PPO were 22.3 and 23.0 mmol L-1 using guaiacol and catechol as substrates. Thermal inactivation kinetics was studied in the temperature range of 60-95 °C. The crude extract of POD and PPO showed D-values of 2.2-60.2 and 1.0-35.2 min; Z-values of 18.7 ± 0.4 and 16.0 ± 0.3 °C; and activation energies (Ea ) of 128.6 and 151.0 kJ mol-1 , respectively. CONCLUSION: POD and PPO showed good stability over a wide range of pH and temperature. As reflected by Z and Ea values, the fruit matrix had no significant influence towards enzyme stability. Designing of thermal process should take into consideration D- and Z-values of the enzymes along with D- and Z-values of microorganisms to obtain a product with better shelf life. © 2017 Society of Chemical Industry.

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, ß-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.

Impact of pulsed light treatment on enzyme inactivation and quality attributes of whole white button mushroom (Agaricus bisporus) and its storage study.

Whole white button mushrooms (WWBM) exhibit a limited shelf-life owing to the oxidative enzymatic browning. Inactivation of polyphenol oxidase-PPO and peroxidase-POD in WWBM and its kinetic behavior were studied using pulsed light(PL) treatment (0.13-1.11 J/cm2). The first-order kinetics explained PL-induced enzyme inactivation. Rate constants(k) for PPO and POD were 3.84 and 2.55 cm2/J. FTIR-analysis revealed secondary-structural changes in partially-purified enzyme. PL-treatment retarded browning, retained phenolics and enhanced vitamin D2. PL-treatment at 1.11 J/cm2 rendered WWBM both microbially and enzymatically stable. The PL-treated WWBM's shelf-life at 4, 20, and 37 °C were 5, 3, and 1 day. At 4 °C, browning increased by 6.1 %; firmness decreased by 55.2 %, while PL-treated mushrooms retained 90.6 % phenolics, 78.9 % antioxidant capacity, and 64.2 % D2 after 5 days. Higher activation energy value confirmed phenolics were most sensitive during storage. PL-technology supports UN Sustainable Development Goals by reducing chemical use, lowering carbon-footprints, minimizing pollution, and enhancing shelf-life, promoting sustainable global trade.

Pulsed light treatment of whole white button mushroom (Agaricus bisporus): Kinetics and mechanism of microbial inactivation and storage study.

The whole white button mushrooms (WWBMs) are highly perishable due to susceptibility to microbial spoilage. This study explored the potential of pulsed light (PL) treatment for decontamination and shelf-life extension of WWBM. WWBM surface was inoculated with Escherichia coli, Listeria monocytogenes, and Aspergillus niger spores (8.1, 8.0, and 8.05 log10 CFU/g, respectively) and tested for inactivation against various PL intensities (fluence 0.13-0.75 J/cm2). The kinetics and mechanism of microbial inactivation were explored, and shelf life was determined at 4, 20, and 37°C. Microbial inactivation increased with increasing PL intensity. PL-induced microbial inactivation was well explained by Weibull model with shape parameters (ß-value) for E. coli, L. monocytogenes, A. niger, aerobic mesophiles, and yeast and mold as 0.87, 0.92, 0.91, 0.89, and 0.94, respectively. PL-treatment at 0.75 J/cm2 resulted in >5-log cycle reduction in all inoculated and natural microorganisms. Exposure to PL led to collapse of cellular structure, ruptured cell wall, and leakage of cellular material in all microorganisms and spores along with alterations in nucleic acid and lipid bands. At 4°C, maximum shelf life of 5 days was achieved when WWBM was exposed at 0.75 J/cm2. The WWBM retained 83.3% phenolics, 83.9% antioxidant capacity, and 77.4% vitamin D2 at 4°C while reducing the polyphenol oxidase and peroxidase activity by 89% and 79%. The degradation rate for quality parameters increased with storage temperature. The activation energy of the browning index affirmed it as the most sensitive quality attribute during storage. The study concluded the potential of PL treatment to prolong the shelf life of WWBM.

Sequential Pulsed Light and Ultrasound Treatments for the Inactivation of Saccharomyces cerevisiae and PPO and the Retention of Bioactive Compounds in Sweet Lime Juice.

Designing a pasteurization con dition for sweet lime juice while ensuring microbial safety, enzymatic stability, and high nutritional quality is crucial for satisfying stakeholder demands. The present research investigates the effects of matrix pH, ultrasound treatments, and sequential pulsed light on the microbial population, enzyme activity, and bioactive chemicals in sweet lime juice. The sequential pulsed light (PL: 0.6-0.84 J/cm2) and ultrasound (US: 0.2-0.4 W/cm3) treatments for sweet lime juice were optimized using response surface methodology (RSM). A three-factor full factorial design was used for this purpose. The independent variables encompassed pH (X1), PL effective fluence (X2, J/cm2), and US intensity (X3, W/cm3). The responses assessed included the inactivation of Saccharomyces cerevisiae (Y1, log cfu/mL) and polyphenol oxidase (PPO: Y2 in %) and the retention of vitamin C (Y3, %). The polynomial models were optimized using numerical optimization to attain the maximum desirability value (0.89). The optimized PL + US sample (0.8 J/cm2 + 0.4 W/cm3, respectively) at pH 3.5 resulted in a 5-log cycle reduction in S. cerevisiae count and a 90% inactivation in PPO activity and retained 95% of its vitamin C content. This optimized sample underwent further analysis, including phenolic profiling, assessment of microbial cell morphology, and examination of enzyme conformational changes. After sequential pulsed-light (0.8 J/cm2) and ultrasound (0.4 W/cm3) treatments, yeast cells showed unusual structural changes, indicating additional targets besides membranes. Following PL + US treatment, the PPO composition changed to 2.7 ± 0.1% α-helix, 33.9 ± 0.3% ß-sheet, 1.4 ± 0.2% ß-turn, and 62 ± 0.7% random coil. Impressively, the optimized PL + US sample maintained a sensory acceptance level similar to that of the untreated sample.

Effect of continuous microwave processing on enzymes and quality attributes of bael beverage.

Bael (Aegle marmelos) beverage was pasteurized using continuous-microwave (MW) and traditional thermal processing and the activity of native enzymes, pulp-hydrolyzing enzymes, bioactive, physicochemical, and sensory properties were analyzed. First-order and linear biphasic models fitted well (R2 ≥ 0.90) for enzyme inactivation and bioactive alteration kinetics, respectively. For the most resistant enzyme, polyphenoloxidase (PPO), the inactivation target of ≥ 90 % was achieved at 90 °C TMW (final temperature under MW) and 95 °C for 5 min (conventional thermal). MW treatment displayed faster enzyme inactivation and better retention of TPC and AOC. MW treatment at 90 °C TMW showed 5.3 min D-value, 90% total carotenoid content, 3.42 crisp sensory score (out of 5), and no or minor change in physicochemical attributes. Thermal and MW treatment caused the loss of 14 and 10 bioactive compounds, respectively. The secondary and tertiary structural modifications of PPO enzyme-protein revealed MW's lethality primarily due to its thermal effects.

Variations in quality attributes of pulsed light-treated table grape juice during refrigerated storage (4°C) and ambient conditions (25°C).

Pulsed light (PL) pasteurization is being explored as a substitute for the conventional thermal pasteurization of juices in recent times due to better retention of nutrients and overall quality. However, the long-term stability of the PL-pasteurized juice must be investigated to promote its application by the industry. The effect of PL treatment (effective fluence of 1.15 J·cm-2) and thermal treatment (90°C for 60 s) on microbial quality, enzyme activity, bioactive compounds, sensory acceptance, and color profile of table grape juice during storage at 4 and 25°C was investigated in this study. The PL pasteurization enhanced the microbial shelf-life of the juice (<6 log10cfu·mL-1) from 5 to 35 days at 4°C. The PL and thermally-pasteurized juice demonstrated a shelf-life of only 10 days when stored at 25°C. The total soluble solids and titratable acidity did not alter significantly throughout the storage period. The peroxidase, polyphenol oxidase, and pectin methylesterase activities were below 10% for the PL and thermally-treated beverage when stored at 4°C. The sensory acceptability of the PL-pasteurized juice after 35 days of refrigerated storage (6.9 ± 0.3) was close to the untreated juice (7.2 ± 0.3) and greater than thermally-treated juice (6.2 ± 0.2). After the 35th day of storage at 4°C, PL-treated grape juice retained 55%, 12%, and 15.3% more phenolics, flavonoids, and antioxidant capacity, respectively, than the thermally-pasteurized juice. Hence, PL pasteurization can effectively prolong the shelf-life of table grape juice while achieving microbial and enzymatic stability, along with high sensory and nutritional appeal. PRACTICAL APPLICATION: Exploring non-thermal methods like pulsed light (PL) pasteurization as a substitute for conventional thermal methods is gaining recognition for its ability to retain nutrients and improve overall juice quality. However, the industry's adoption depends on understanding the shelf-stability of PL-pasteurized juice. This study specifically investigates the practical applications of PL treatment in comparison with conventional thermal treatment in enhancing microbial safety and enzymatic stability in table grape juice. The findings contribute insights into optimizing the shelf life of table grape juice and preserving its quality, supported by microbial, enzymatic, and sensory evaluations.

A sequential approach of alkali enzymatic extraction of dietary fiber from rice bran: Effects on structural, thermal, crystalline properties, and food application.

Rice bran is abundant in dietary fiber and is often referred to as the seventh nutrient, recognized for its numerous health benefits. The objective of the current study is to investigate the extraction of both soluble and insoluble dietary fiber from defatted rice bran (DRB) using an alkali-enzymatic treatment through response surface methodology. The independent variables like substrate percentage (5-30 %), enzyme concentration (1-50 µL/g), and treatment time (2-12 h) and dependent variables were the yield of soluble and insoluble DF. The highest extraction yield was observed with alkali enzyme concentration (50 µL/g) treatment, resulting in 2 % SDF and 59.5 % IDF at 24 h of extraction. The results indicate that cellulase-AC enzyme aids in the hydrolysis of higher polysaccharides, leading to structural alterations in DRB and an increase in DF yield. Furthermore, the disruption of intra-molecular hydrogen bonding between oligosaccharides and the starch matrix helps to increase in DF yield, was also confirmed through FTIR and SEM. The extracted DF soluble and insoluble was then used to develop rice porridge. Sensory evaluation using fuzzy logic analysis reported the highest scores for samples containing 0.5 % insoluble DF and 1.25 % soluble DF.

Effect of dehydration and pulsed light treatment on decontamination of minced onions: Microbial safety and physicochemical properties.

Microbial contamination of dehydrated onion products is a challenge to the industry. The study focused on opting for a suitable drying condition for minced onion and exploring the decontamination efficacy of pulsed light (PL) treatment conditions for the dehydrated product. The minced onions were hot air dried at 55-75°C for 280 min. The drying condition selected was 195 min at 75°C with a final water activity of 0.5 and moisture content of 7% (wet basis [w.b.]). The weight losses, browning indexes (BI), shrinkage volumes (%), and thiosulfinate content were considered. The dehydrated product was exposed to PL treatment corresponding to an effective fluence range of 0.007-0.731 J/cm2. A fluence of 0.444 J/cm2 (1.8 kV for 150 s) achieved 5.00, 3.14, 2.96, and 2.98 log reduction in total plate count, yeast and mold count, Bacillus cereus 10876, and Escherichia coli ATCC 43888, respectively. The PL-treated sample (0.444 J/cm2) produced a microbially safe product with no significant difference in the moisture contents (%w.b.) and water activity (aw) from the untreated dehydrated sample. Further, a 30.9% increase in the BI and a 4.25% depletion in thiosulfinate content were observed after PL treatment. An optimum drying combination (75°C for 195 min) of minced onion followed by decontamination using pulsed light treatment at 0.444 J/cm2 fluence satisfies the microbial safety and quality. PRACTICAL APPLICATION: Dehydrated minced onion can be used for dishes requiring low water content and short cooking time. It is helpful during shortages, high price fluctuations, and famines.

Advances in the novel and green-assisted techniques for extraction of bioactive compounds from millets: A comprehensive review.

Millets are rich in nutritional and bioactive compounds, including polyphenols and flavonoids, and have the potential to combat malnutrition and various diseases. However, extracting these bioactive compounds can be challenging, as conventional methods are energy-intensive and can lead to thermal degradation. Green-assisted techniques have emerged as promising methods for sustainable and efficient extraction. This review explores recent trends in employing green-assisted techniques for extracting bioactive compounds from millets, and potential applications in the food and pharmaceutical industries. The objective is to evaluate and comprehend the parameters involved in different extraction methods, including energy efficiency, extraction yield, and the preservation of compound quality. The potential synergies achieved by integrating multiple extraction methods, and optimizing extraction efficiency for millet applications are also discussed. Among several, Ultrasound and Microwave-assisted extraction stand out for their rapidity, although there is a need for further research in the context of minor millets. Enzyme-assisted extraction, with its low energy input and ability to handle complex matrices, holds significant potential. Pulsed electric field-assisted extraction, despite being a non-thermal approach, requires further optimization for millet-specific applications, are few highlights. The review emphasizes the importance of considering specific compound characteristics, extraction efficiency, purity requirements, and operational costs when selecting an ideal technique. Ongoing research aims to optimize novel extraction processes for millets and their byproducts, offering promising applications in the development of millet-based nutraceutical food products. Therefore, the current study benefits researchers and industries to advance extraction research and develop efficient, sustainable, and scalable techniques to extract bioactive compounds from millets.

Optimization of fermentation conditions of synbiotic legume-based beverages and study of their antimicrobial and proteolytic activity.

The objective of the present work is to optimize fermentation conditions for a set of three legume-based synbiotic beverages made from green mung and red kidney beans, namely GMB (100% mung bean); RKB (100% kidney bean); and KB (7:3, kidney bean: mung bean) to attain desirable quality attributes. Face-centered composite design (FCCD) was applied using fermentation time and temperature as independent variables. The responses, namely, pH, protein digestibility (PD), and total viable count (TVC) of probiotic Lacticaseibacillus casei ATCC 335, were optimized using response surface methodology (RSM) followed by numerical optimization. The optimization was based on maximizing the desirability, which connected the responses and importance. The experimental and predicted values were similar, and the model was valid for all beverages with R2  > 0.9. The optimized condition suggested that fermentation at 20°C for 18 h in the case of KB and GMB and 21 h for RKB would lead to desired pH (6.0-6.5), maximum PD (> 60%), and highest TVC (> 8 log CFU/ml). A significant reduction in antinutritional factors (ANFs), namely, tannin (20-44%), saponin (43-52%), and phytate (43-46%) from an initial value of around 0.30, 0.40, and 0.50 mg/L respectively, for all the beverages at optimized fermentation conditions was observed. Similarly, a slight loss of < 3.5% in total phenol content (TPC) was seen. Additionally, good proteolytic and antibacterial activity was observed, with KB being the best. Hence, all developed legume-based synbiotic beverages exhibit desirable goals when subjected to optimized fermentation conditions and enhanced functionality. PRACTICAL APPLICATION: When subjected to optimized fermentation conditions, the developed synbiotic legume-based beverages can be used as a potential functional food in the nondairy beverage industry with added health benefits and new tasting flavors.

Formulation of a mixed fruit beverage using fuzzy logic optimization of sensory data and designing its batch thermal pasteurization process.

The study aims to formulate a mixed fruit beverage through sensory analysis, and the composition was optimized using a fuzzy logic algorithm. The fuzzy optimization algorithm was developed using a modified Takagi and Sugeno's approach, polynomial mixture modeling, and nonlinear solver engine. The optimized blend consisted of amla juice, pineapple juice, and coconut water in 14.3, 63.0, and 22.7%, respectively. Further, the batch thermal treatment was carried out within 50 to 95 °C for an isothermal holding time of 1 s to 10 min, and pasteurization condition for the beverage was estimated from kinetic modeling. The concept of thermal pulse inactivation due to non-isothermal heat-up-time and cool-down-time has been introduced within the process time calculation. From the kinetic study, polyphenoloxidase enzyme appeared to be the most resistant entity towards inactivation among all the natural microbiota and quality deteriorating enzymes. Pasteurization in terms of achieving a 5D reduction of both aerobic mesophilic and yeast-mold counts was attained over a range of 80 to 95 °C for 10.2 + 1.4 to 3.1 + 2.0 min (1.4 and 2.0 min = heat-up-time + cool-down-time), respectively. The 90% inactivation of both polyphenoloxidase and peroxidase enzymes was obtained over a range of 90 to 95 °C for 12.8 + 1.7 to 8.4 + 2.0 min, respectively. While obtaining both the microbial and enzyme stability at the isothermal condition of 95 °C for 8.4 min, the corresponding retention in ascorbic acid, total phenolics, and antioxidant capacity were observed as 49.7, 63.0, and 61.4%, respectively. PRACTICAL APPLICATION: In this work, the formulation of a fruit blend was optimized through an intelligent optimization technique (fuzzy algorithm) applied to the sensory data set. The approach for calculating thermal processing time or pasteurization condition provides a new dimension with better precision. The thermal treatment condition of 95 °C for 10 min can be used for this mixed beverage to achieve both microbial stability (5-log reduction) and enzyme stability (90% reduction). The presented study can be used as a reference for other similar beverages to achieve a complete process design from basic formulation optimization to thermal (batch-type) processing conditions.

Fermentative Production of Naringinase from Aspergillus niger van Tieghem MTCC 2425 Using Citrus Wastes: Process Optimization, Partial Purification, and Characterization.

Enzymatic hydrolysis of naringin by the action of naringinase is one of the standard practices adopted in the citrus fruit juice industry for debittering. In the present study, a submerged fermentation condition was optimized for producing naringinase from Aspergillus niger van Tieghem MTCC 2425. As per Placket-Burman design, pH (3-5), incubation temperature (26-30 °C), and inducer concentration (12-18 g·L-1) were the most important factors influencing the naringinase production. Naringin from citrus waste was used as an inducer. A rotatable central composite design was employed on these three variables and the numerical optimization predicted that fermentation at 29.8 °C, pH 4.7, and inducer concentration of 14.9 g L-1 would yield a maximum naringinase activity of 545.2 IU g-1. During partial purification, ion exchange chromatography led to a 9.92-fold increase in enzyme activity resulting a specific activity of 5460 IU g-1 with an activity recovery of 17%. As reflected by SDS-PAGE profile, the partially purified naringinase showed the molecular weight bands of 10-20, 65, and 80 kDa, respectively. The purified form of enzyme showed optimum stability at pH 5 and 50 °C. The naringinase activity was completely retained up to 150 days when stored at 4 °C.

Effect of thermal and non-thermal techniques for microbial safety in food powder: Recent advances.

Food powders are appreciated worldwide, as it enables food to be preserved for an extended period without significant loss of quality, even under the ambient storage condition. However, it is evidenced that the development of resistant microbial spore and viable microbial cells is a matter of concern even in low moisture foods like food powders. For microbial inactivation, the strategy generally applied is the implication of conventional preservation methods, such as heat treatment which is greatly accompanied by degradation of nutritional organoleptic properties. To overcome the shortcomings of conventional thermal processing, a set of advanced or emerging technologies are being developed which can inactivate the microbial spores and viable microbial cells capable of surviving with maximum retention in the nutritional or organoleptic profile. The examples include infrared heating, microwave heating, radiofrequency heating, instant control pressure drop technology, high-pressure processing, pulsed electric field, pulsed light, ozone processing, and cold plasma. In this review, the potential of different advanced thermal and non-thermal technologies towards the inactivation of spores and viable cells of microorganisms in food powders has been highlighted precisely along with their mechanism of action. The summary of the literature encompassing the use of different processing techniques will help the readers to understand the underlying mechanism of microbial inactivation associated with each processing techniques applied to powders. Eventually, this information will help them to select the suitable technique (individual or in combination with another counterpart) to inactivate spores and viable cells in a specific food powder.

Rheological, functional and morphological characterization of reconstituted Aloe vera gels at different levels of pH and concentration: Novel concepts of reconstituted Aloe vera gels formation.

In this study, firstly, gelation process and its optimization at different pH (3-7) and concentration (0.2-1.6%, w/v) on the viscoelastic behavior of reconstituted Aloe vera (A. vera) samples were studied using response surface methodology (RSM). The optimum condition obtained by numerical optimization for the formulation of reconstituted samples was 1.6%, w/v at pH 7 with desirability of 0.84. Secondly, structural alteration of the reconstituted A. vera gels were evaluated using FTIR, SEM, and TEM at particular pH (3-7) and concentration (0.2-1.6%, w/v). The FTIR spectrum of reconstituted hydrogels showed formation of new hydrogen bond at 3600-3000 cm-1 and deacetylation of acemannan at 1740 cm-1 with increase in A. vera concentration. Moreover, SEM and TEM micrograph images of A. vera xerogel at lower concentrations (0.2-0.4%, w/v) evidenced the intact surface morphology and formation of clumps and at higher concentration (0.8-1.6%, w/v), exhibited rope-like network patterns and composed of spherical aggregates.

Response Surface Optimization of Process Parameters and Fuzzy Analysis of Sensory Data of High Pressure-Temperature Treated Pineapple Puree.

The high-pressure processing conditions were optimized for pineapple puree within the domain of 400-600 MPa, 40-60 °C, and 10-20 min using the response surface methodology (RSM). The target was to maximize the inactivation of polyphenoloxidase (PPO) along with a minimal loss in beneficial bromelain (BRM) activity, ascorbic acid (AA) content, antioxidant capacity, and color in the sample. The optimum condition was 600 MPa, 50 °C, and 13 min, having the highest desirability of 0.604, which resulted in 44% PPO and 47% BRM activities. However, 93% antioxidant activity and 85% AA were retained in optimized sample with a total color change (∆E*) value less than 2.5. A 10-fold reduction in PPO activity was obtained at 600 MPa/70 °C/20 min; however, the thermal degradation of nutrients was severe at this condition. Fuzzy mathematical approach confirmed that sensory acceptance of the optimized sample was close to the fresh sample; whereas, the thermally pasteurized sample (treated at 0.1 MPa, 95 °C for 12 min) had the least sensory score as compared to others.

Empirical model based on Weibull distribution describing the destruction kinetics of natural microbiota in pineapple (Ananas comosus L.) puree during high-pressure processing.

High pressure inactivation of natural microbiota viz. aerobic mesophiles (AM), psychrotrophs (PC), yeasts and molds (YM), total coliforms (TC) and lactic acid bacteria (LAB) in pineapple puree was studied within the experimental domain of 0.1-600 MPa and 30-50 °C with a treatment time up to 20 min. A complete destruction of yeasts and molds was obtained at 500 MPa/50 °C/15 min; whereas no counts were detected for TC and LAB at 300 MPa/30 °C/15 min. A maximum of two log cycle reductions was obtained for YM during pulse pressurization at the severe process intensity of 600 MPa/50 °C/20 min. The Weibull model clearly described the non-linearity of the survival curves during the isobaric period. The tailing effect, as confirmed by the shape parameter (ß) of the survival curve, was obtained in case of YM (ß<1); whereas a shouldering effect (ß>1) was observed for the other microbial groups. Analogous to thermal death kinetics, the activation energy (Ea, kJ·mol(-1)) and the activation volume (Va, mL·mol(-1)) values were computed further to describe the temperature and pressure dependencies of the scale parameter (δ, min), respectively. A higher δ value was obtained for each microbe at a lower temperature and it decreased with an increase in pressure. A secondary kinetic model was developed describing the inactivation rate (k, min(-1)) as a function of pressure (P, MPa) and temperature (T, K) including the dependencies of Ea and Va on P and T, respectively.