Effect of Heat Processing on the Texture Profile of Canned and Retort Pouch Packed Oil Sardine (Sardinella longiceps) in Oil Medium

ABSTRACT: Sardine in oil was canned at 3 different Lethality values (F₀ 5,7, and 9) in retort pouches and aluminum cans in stationary retort. Process time calculations were done mathematically to find out the actual process time. Sardine in oil processed in retort pouches had a lower process time compared with aluminum cans for each F₀ value. Instrumental texture analysis was done using a food texture analyzer to study the effect of thermal processing on the texture of thermally processed sardine in oil in aluminum cans and retort pouches. As the F₀ value and cook value increased in both the retort pouches and aluminum cans, the textural properties showed a decreasing trend. Hardness of the product canned in both aluminum cans and retort pouches decreased with increase in F₀ values.     

HEATING BEHAVIOR AND QUALITY FACTOR RETENTION IN A CANNED MODEL FOOD AS INFLUENCED BY THERMAL PROCESSING IN A ROTARY RETORT

Heat penetration data were obtained for a canned model food (gelatinized starch) during processing in a rotary retort under various conditions (retort temperature, 110–130C; rotation speed, 10–20 rpm, can headspace 6.4–12.8 mm and starch concentration, 3–4%) to establish thermal processes with an equivalent lethality (F₀ value) of 10 min. Apparent viscosity and Hunter L, a and b values were experimentally evaluated both before and after each run. The percentage of selected quality factors (nutrients, color) retained at each processing condition was estimated using the heat penetration data and documented kinetic parameters for each quality factor. The study indicated that the heating behavior was influenced (p < 0.05) by all factors except can headspace. Higher temperatures and higher rotation speeds favored better retention of quality factors and reduction in process times.     

Artificial neural network model for prediction of cold spot temperature in retort sterilization of starch-based foods

An artificial neural network (ANN) model was developed for prediction of the cold spot temperature profile during retort processing using starch dispersion (STD) as a model food. STDs of different concentrations were prepared by mixing corn starch powder with distilled water at 90 °C for 30 min. Each of the partially gelatinized STDs thus prepared was filled in retort pouches and processed in a retort under various combinations of holding temperature, holding time, and rotational speed. Thermocouples were inserted into selected pouches one by one to monitor the cold spot temperature at regular intervals. The profiles of cold spot temperature together with retort temperature thus obtained were served to ANN modeling as training or validation data. Back-propagation network was chosen as the network model. Input variables for the model were current and past temperatures of the cold spot (T_n, T_n−1, and T_n−2) and current retort temperature θ_n and current time t_n. Output was the temperature of the cold spot at the next time step T_n+1. A model with 2 hidden layers, which contained 11 and 15 nodes, respectively, was the best among the models tested. Using the model developed, prediction of a whole profile of the cold spot temperature was tested, starting from temperature data of the first three time steps with a whole profile of retort temperature monitored. The results showed very good performance of the model, relative errors for F₀ value prediction being less than 2%.     

Thermal processing of prawn 'kuruma' in retortable pouches and aluminium cans

Prawn ‘kuruma’ was prepared from Indian white shrimp (Fenneropenaeus indicus), packed in conventional 301 × 206 and 401 × 411 aluminium cans and in thin profile retort pouches having a three-layer configuration of 12.5 μ polyester, 12.5 μ aluminium foil and 85 μ cast polypropylene of size 16 × 20 cm and 17 × 30 cm. The physico-chemical tests conducted on these containers showed their suitability for thermal processing. Prawn to kuruma ratio of 65:35 was maintained in all the containers and heat processed to equal lethality in an over pressure autoclave with the facility to record the time–temperature data, F₀ value and cook value. The process time was calculated by using formula method. The processing in 16 × 20 cm and 17 × 30 cm retortable pouch resulted in 35.67% and 56.56% reduction in process time compared with 301 × 206 and 401 × 411 cans, respectively, with equal pack weight. The amino acid content did not vary considerably in both containers. In the canned samples the reduction of sulfhydryl content was 50.54% more when compared with the pouched product. Products packed in pouches were found to be superior to canned products with regard to sensory and textural attributes such as colour, firmness, hardness, chewiness, and overall acceptability.     

Heating Characteristics of Whole Kernel Corn Processed in a Steritort

Cans of whole kernel corn in brine and vacuum-packed corn were heated in an FMC Steritort and in a still retort. Two can sizes for each product were processed to simulate two commercial agitating processing machines. The sterilization values (F_o) and heat penetration factors (j, f_h, f₂) were determined from time-temperature data and were influenced by reel rotational speed, corn fill weight, and brine fill or container headspace. For both products, optimum heat penetration for agitated processing occurred at a ratio of brine-to-corn fill weights of about 35% (normal for vacuum-packed products). Above a threshold value, increasing reel rotational speed did not significantly enhance heating, and with the accompanied reduction in retention time in continuous retorts, F_o values would actually be lowered. Sterilization values were somewhat reduced because of overfills of both corn and brine. For the vacuum-packed product, vacuum level significantly influenced heat penetration only for the still processes.     

The effects of static,oscillating, and oscillating with dwell time retort motions on the rate of heat penetration of a food simulant processed in a pouch

The objective of this work was to study the effect of three different retort motions on the rate of heat penetration in pouches. Pouches were processed in a water spray batch retort system using static, oscillating continuously at a speed of 10.5 rotations per minute (RPM) with an angle of 15 degrees, and oscillating at 10.5 rpm at a 15 degree angle with a 15‐s hold. There was no difference in the rate of between static and oscillating processes (p > .05). There was a difference in the between static and oscillating with a hold processes (p < .05). At a 90% confidence interval, there was also a difference between the rate of heat penetration between the oscillating and oscillating with a hold processes (p > .05, p = .056). The location of the pouches on the retort rack did not influence the rate of heat penetration within the three methods or between the three methods (p > .05).

Practical applications

Despite novel technological developments for creating sterile shelf stable products, thermal processing is still the most reliable method. Creating innovation within thermal processing by using different methods of motion to create faster heating profiles can improve the quality of products. This research can be used for optimizing retort processes for food products in pouches. Processing with motion has been seen to reduce the processing time which can increase nutrient retention, reduce thermal abuse, and ultimately save money and increase production. Retort food manufacturers can use oscillating and hold motion to make higher quality products in less time than static motion.     

Heat Penetration in Canned Mussels during Agitated Retorting

Heat penetration to cans of mussels in brine processed in an agitating retort was studied. The heating lag factor, j, and the time for the heating curve to traverse a log cycle, f_h, as a function of the rotational speed, the headspace presence, and the come-up time were determined. Heat penetration rates increased with end-over-end rotation at low rotational speeds. The presence of headspace produced significant improvements in heat penetration. Transient temperature profiles for this product were relatively short; therefore, improvements in heat penetration would only be significant when retort come-up times are short.     

Comparison of free/bi-axial,fixed axial,end-over-end and static thermal processing effects on process lethality and quality changes in canned potatoes

Thermal processing as the most prevalent food preservation technique has been extensively studied and used for years. Different modes of agitation that can be employed in the canning process are characterized by relatively different, heat impacts and their associated quality changes. Hence, the main objective of this study was to evaluate the impact of different retort conditions on lethality (F_o), color and textural changes in potato cubes. Process variables employed were: retort temperature: 115, 120, 125 ºC; agitation orientations: vertical (end-over-end) and horizontal (fixed and bi-axial); agitation speed: 0 (static), 10, 20 rpm. A water immersion single basket rotary retort was retrofitted to simultaneously accommodate agitating modes of rotation. Accumulated process lethality values were calculated for each experimental run. Color quality in terms of parameters such as, yellowness (b-value), total color difference (ΔE values) and textural quality in terms of hardness values were compared for the particles processed under each condition. All process variables had a significant (p < 0.05) influence on F_o, color and texture parameters of potato particles. The quality changes were found to correlate well with the accumulated F_o values achieved during processing. As can be expected, the quality loss increased with an increase in F_o and vice versa.     

Comparison of Sterilization Values from Heat Penetration and Spore Count Reduction in Agltating Retorts

Sterilization values from heat penetration (F_o) and spore count reduction (IS) were simultaneously measured in 7% food starch heated in 300 × 404 cans in an agitating retort. Thermal inactivation of the spores of Bacillus stearothermophilus was characterized by a 4 min lag period, a D_121.1 of 2.5 min, and a z of 8.2C°. Differences between IS and F_o were influenced by retort temperature, lag in inactivation, and z-value, for F_o values from 5 to 15. IS was generally higher than F_o for retort temperatures above 121.1°C. F values using the z of 8.2°C compared favorably to IS (corrected for the inactivation lag period) for retort temperatures between 115.0° and 126.1°C.     

Water Velocity Effect on Heat Penetration Parameters During Institutional Size Retort Pouch Processing

Institutional size retort pouches (15 × 12 × 1) filled with 10% bentonite were processed in water with overriding air pressure. The heat penetration parameter, f_h, was measured at seven flow rates from 10 gal/min (Re = 3000) to 110 gal/min (Re = 33000). Apparent convection heat transfer coefficients (h-values) were calculated. Significant differences were found for both the h-value and observed f_h value as a function of flow rate. The h-values ranged from 33–48 BTU/hr ft² F and the observed f_h values ranged from 23.0–20.1 min for 10 and 110 gal/min, respectively.     

Quality of ready to serve tilapia fish curry with PUFA in retortable pouches

Studies on the physical, chemical, and microbiological qualities of fresh tilapia meat revealed its suitability for the preparation of ready to eat fish curry packed in retort pouches. Studies on the fatty acid profile of tilapia meat suggest fortification with polyunsaturated fatty acid (PUFA) to increase the nutritional value. Based on the commercial sterility, sensory evaluation, color, and texture profile analysis F(0) value of 6.94 and cook value of 107.24, with a total process time of 50.24 min at 116 °C was satisfactory for the development of tilapia fish curry in retort pouches. Thermally processed ready to eat south Indian type tilapia fish curry fortified with PUFA was developed and its keeping quality studied at ambient temperature. During storage, a slight increase in the fat content of fish meat was observed, with no significant change in the contents of moisture, protein, and ash. The thiobarbituric acid (TBA) values of fish curry significantly increased during storage. Fish curry fortified with 1% cod liver oil and fish curry without fortification (control) did not show any significant difference in the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), during thermal processing and storage. Sensory analysis revealed that fortification of fish curry with cod liver oil had no impact on the quality. Tilapia fish curry processed at 116 °C and F(0) value of 7.0 (with or without fortification of cod liver oil) was fit for consumption, even after a period of 1-y storage in retort pouch. PRACTICAL APPLICATION: Tilapia is a lean variety of fish with white flesh and therefore an ideal choice as raw material for the development of ready to serve fish products such as fish curry in retort pouches for both domestic and international markets. Ready to eat thermal processed (116 °C and F(0) value of 7.0) south Indian type tilapia fish curry enriched with PUFA and packed in retort pouch was acceptable for consumption even after a storage period of 1 y at ambient temperature.     

Heating Rates in Flexible Packages Containing Entrapped Air During Overpressure Processing

Experiments were performed in two steam/air retorts and one water immersion retort to test the influence of included air on heating rate index (f_h) values at the center of thin plastic bricks packaged in retort pouches and processed under various temperature and overpressure conditions. In general, high air overpressures (>80 kPa) allowed up to 30 mL air to be included with no detrimental effect on heating rates; however, even small amounts of entrapped air (<5 mL) degraded heat transfer when processed at low air overpressures (<40 kPa). Processing medium and retort type were important factors in the sensitivity of heating rate to increases of air volumes beyond a threshold value.     

Ascorbic Acid Retention in Retort Pouched Green Beans

The L-ascorbic acid (AA) retention in and sensory quality of green beans processed under home-canning conditions in retort pouches and metal cans were compared. Green beans processed in cans retained slightly more AA than that processed in the pouches, possibly due to overprocessing of the pouched product. Metal cans offered better AA retention in the green beans than the retort pouches during 11 wk of storage at 21°C, due mainly to a higher rate of AA degradation occurring in the pouched product during the first week of storage. Sensory evaluation showed that the retort pouched beans were significantly better (p < 0.05) than the canned green beans in flavor, texture, and overall acceptance, but not in color.     

RETORTABILITY of THIN-WALLED ALUMINUM CONTAINERS PRESSURIZED WITH ADDED LIQUID NITROGEN (LN2)

Studies were conducted to investigate the effect of initial container pressure on heat penetration parameters using flexible aluminum containers. A pilot scale liquid nitrogen dispenser, regulated to discharge a fine stream of liquid nitrogen (LN₂), provided approximately 10 to 15 psi pressure within the container prior to end‐over‐end processing in a computer‐controlled retort using water immersion with 32 psi over pressure. Thermal process parameters including the heating rate index (f_h), lag factor (j_h), the cumulative lethality (F_o), cook‐value (C_o) and the overall heat transfer coefficient (U_o) were examined in relation to retort temperature (241–261F), rpm (0–15 rpm) and product initial temperature (54–121F) using 5% w/w bentonite suspension with or without liquid nitrogen. Generally, containers with added liquid nitrogen had no impact on evaluated data compared to their counterparts without LN₂ under similar experimental conditions. Estimated overall heat transfer coefficient (U_o) compared favorably with published data, while the C_o/F_o ratio decreased with increasing temperatures as expected. Product cold spot location migrated in either upward or downward direction depending on the mode of heat transfer. Although added LN₂ generally had no limiting effect on both heat transfer and heat penetration data, processing aluminum containers with high initial pressure at high retort temperatures could create excessively high internal pressure that could compromise container seam integrity.     

THERMAL RESISTANCE OF BACILLUS STEAROTHERMOPHILUS SPORES IN DRIED PASTA AT DIFFERENT STAGES OF REHYDRATION

The thermal resistance of Bacillus stearothermophilus spores at different stages of rehydration was examined. Inoculation was achieved by rehydrating pasta samples in water containing 1‐mL spore crop (10⁶ spores/mL); the product was heat sealed in sterile pouches and processed in a laboratory retort. Thermal inactivation of spores was carried out using 10 time intervals at 121C for moisture contents, 70, 90, 105, 115, 125 and 145% dry basis. The death curves obtained consisted of two phases, an initial rapid decline (1.5 to 2.6 log reductions) followed by a slower, linear decrease of survivors from which the decimal reduction time (D value) was calculated. D₁₂₁ values were found to decrease with increasing moisture content and ranged from 4.6 to 6.5 min. The thermal resistance constant (z value) was examined to assess the effect of temperature (110–125C) on lethality. z values decreased with increasing moisture content and ranged from 10.7 to 15.6C. The results of this study demonstrate that temperature and moisture content influence the effectiveness of the intended heat process. For products that are rehydrated during heat treatment, the moisture content of the product is a critical factor. Therefore, if complete rehydration is not achieved, this may result in the heat process being less effective for the destruction of microorganisms, which may have implications in regard to food safety.     

A sterilisation Time–Temperature Integrator based on amylase from the hyperthermophilic organism Pyrococcus furiosus

A candidate Time–Temperature Integrator (TTI) which is potentially suitable for use in validation of sterilisation processes was identified and tested. The TTI was based on the highly thermostable amylase produced from the extracellular medium of a Pyrococcus furiosus fermentation: this organism grows at temperatures in the region of 100 °C. Kinetic properties for the amylase following inactivation by heat showed it to be suitable for use as a sterilisation TTI. Isothermal kinetic data at 121 °C and non-isothermal kinetic data over the range 121 to 131 °C were determined. A decimal reduction time (D_T-value) at 121 °C of 24 min was calculated from isothermal tests and a range from 18.1 to 23.9 min from non-isothermal tests. A z-value of 10 °C was estimated from non-isothermal tests. Thus, sterilisation values (F₀) estimated from this TTI would be similar to F₀-values representative of the destruction of Clostridium botulinum spores. Industrial measurements under non-isothermal conditions were conducted in metal cans processed in an FMC reel and spiral cooker–cooler and a bar simulator, and also in plastic pouches processed in a Lagarde steam-air retort.Industrial relevanceMany food processes, such as canning, are based upon thermal sterilisation of the food material. The development of a reliable Time–Temperature Integrator for such a process would be industrially valuable by providing a simple way of validating such processes. This study demonstrates the feasibility of one such TTI.     

Heat Penetration for Sliced Mushrooms in Brine Processed in Still and Agitating Retorts with Comparisons to Spore Count Reduction

Retail and institutional cans of sliced mushrooms in brine were heated in still and agitating retorts. The F_o values and heat penetration factors were determined from time-temperature data for various brine headspaces, reel speeds, and fill weights. Mushroom fill weight was the more critical parameter for simulated Sterilmatic and still processes. In the Sterilmatic, increasing the fill weight by 17% reduced the F_o from 9.5 to 5.7 min. Compacting mushrooms during filling reduced the F_o from 21.8 to 4.3 min in the still retort. A microbial method of process determination was conducted for selected agitated processes to compare with heat penetration. The integrated sterilization value, based on spore count reduction, exceeded F_o by as much as 7.2 min in the 603 × 700 can, indicating the two sterilization values are not directly comparable.     

Optimizing Thermal Process for Canned White Beans in Water Cascading Retorts

Based on thermal degradation kinetics and heat transfer expressed as the Ball formula method, a simplified approach was used to optimize sterilization processes for thermal softening of white beans (Phaseolus vulgaris, subsp. nanus Metz., variety Manteca de Leon) Constant retort profiles in a still and end-over-end rotary water cascading retort (Barriquand Steriflow) were used. Quality attributes of beans processed at the optimum were evaluated by a trained taste panel and by a tenderometer. Both approaches could distinguish (P<0.01) between attributes of products from optimal rotary and still processes. End-over-end rotation resulted in faster heat penetration and better quality retention of beans. Texture of white beans processed at 4° or 8°C from the optimal temperature could be distinguished (P<0.01) by the sensory panel and by the tenderometer.     

Expressing the equivalence of non‐isothermal and isothermal heat sterilization processes

Currently, the sterility of heat‐processed food and pharmaceuticals is assessed in terms of an F₀ value, based on the equivalence of the heat treatment to an isothermal process at a reference temperature. This F₀ value, however, has a meaning if, and only if, the inactivation kinetics of the targeted spores (or cells) follow a first‐order relationship and the temperature dependence of the D value, the reciprocal of the rate constant, is log‐linear. There is growing evidence that these conditions are not satisfied by many spores, including those of Clostridium botulinum and vegetative cells. Consequently, a replacement for the F₀ value is proposed in the form of a momentary equivalent time at the reference temperature based on the actual survival pattern of the spores, which need not be log‐linear. This equivalent time can be calculated together with the theoretical survival ratio in real time, thus enabling an operator to monitor the lethality of ongoing industrial heat processes. The concept is demonstrated with published survival data of C. botulinum, for which the Weibullian and log‐logistic models served as primary and secondary models, respectively. The safety factor according to the proposed method is in the number of added minutes of processing, beyond the theoretical time needed to reduce the survival ratio of the targeted spores or cells to a level that would produce practical (or commercial) sterility. Copyright © 2006 Society of Chemical Industry     

Textural and sensory characteristics of retort-processed freshwater prawn (Macrobrachium rosenbergii) in curry medium

Freshwater prawn in curry was thermally processed to three F₀ values of 6, 8, and 9 at 116°C. Total process times for F₀ values of 6, 8, and 9 were 53, 57, and 63 min, respectively. The cook value (CV) obtained at F₀ values of 6, 8, and 9 was 87.53, 107.93, and 117.55 min, respectively. Instrumental texture profile analysis revealed that except springiness, the values of hardness, gumminess, and chewiness decreased as the F₀ values increased. CIELAB values of L*, b*, and a* increased as the F₀ values were increased. The organoleptic evaluation scored the highest for the product processed to F₀ 7 min.