Assessment of Previous Heat Treatment of Laboratory Heat-Processed Meat and Poultry using a Commercial Enzyme System

The APIZYM enzyme system was assessed with respect to: enzyme activity in aqueous and saline extract filtrates from raw and heat processed (60° and 71.1°C) beef; effect of rate of heating (0.2–0.3°C, 0.4–0.5°C, and 0.9–1.0°C/min) to internal temperatures of 66.7°, 67.8°, 68.9°, 70.0°, and 71.1°C and holding times of 0, 15, 30, 45, and 60 min at these temperatures on residual enzyme activity; reduction of enzyme assay incubation time; and reproducibility of the system. Results showed that slightly higher enzyme activity in heated samples was obtained with 0.9% saline extraction compared to water. Greater enzyme activity was observed in filtrates from pork samples heat-processed at a fast rate than at a slow rate. Enzyme activity could be detected after 2 hr incubation, but 4 hr were needed for the enzymes to react with their respective substrates. The system was found to be reproducibile. The results of this study also indicated the potential of using leucine aminopeptidase as an indicator enzyme for determining the adequacy of heat treatment of meat and poultry products.     

Transaminase (AST/GOT and ALT/GPT) Activity in Ground Beef as a Means of Determining End-point Temperature

Thermal processing conditions [rate of temperature increase, 0.35°C or 3.5°C/min; end-point temperature (EPT), 57.2, 71.1, and 79.4°C; dwell time, 0 and 30 min; and enzyme extraction medium (deionized water, 0.9% saline, and pH 7 buffer)] affected glutamic oxalacetic transaminase (GOT; aspartate aminotransferase, E.C. 2.6.1.1) and glutamic pyruvic transaminase (GPT; alanine aminotransferase; E.C. 2.6.1.2) activity in thermal treated ground beef samples. There was greater loss of GOT activity in samples heat processed at 0.35°C/min than samples heat processed at 3.5°C/min with depletion nearly to zero between 71.1 and 79.4°C. More GOT activity was noted when samples were extracted with 0.9% saline solution. GPT activity was low in all samples and was present after heating to 79.4°C.     

Assessment of Previous Heat Treatment Given to Semi-Commercially and Commercially Prepared Meat and Poultry Products Using the "APIZYM" System

A micromethod enzyme system (APIZYM) designed for the detection of 19 individual enzymes was used to assess the previous heat treatment given to a variety of meat and poultry products. Filtrates were obtained from 0.9% saline extracts of heat- processed product. Results indicated the possibility of using the APIZYM system as a screening procedure for monitoring the adequacy of heat-treatment of semi-commercially and commercially prepared products, with the exception of deli-type roast beef and products where several processing time/ temperature combinations were involved. In these tests, leucine aminopeptidase appeared to be a more sensitive indicator enzyme than the currently used acid phosphatase procedure.     

Effect of hydrothermal processing on colour,antioxidant and free radical scavenging capacities of edible Irish brown seaweeds

The effect of heat processing on change in colour (ΔE), level of bioactive compounds and overall antioxidant capacity in raw and heat‐processed edible Irish brown seaweeds was investigated. Raw seaweeds were heated at 85–121 °C for 15 min in an autoclave and extracted with 60% methanol. In comparison with raw seaweeds for all the species studied, heating increased total phenol (TPC) (1.6‐ to 1.9‐fold) and total tannin (TTC) (1.3‐ to 2.6‐fold) at 95 °C, while total flavonoid (TFC) (1.6‐ to 3.3‐fold) and total sugar (TSC) (1.9‐ to 4.3‐fold) at 85 °C. Similarly, EC₅₀ value reduced in case of DPPH^? scavenging (30.7–51.8%), metal chelating ability (FIC) (27–67.8%) and H₂O₂ scavenging capacity (13.3–16.1%) at 95 °C, while reduction in lipid peroxidation (10.8–31.5%) observed at 85 °C. Results showed that heating affects content of bioactive compounds as well as beneficial biological activity associated with these compounds, which can suggest new processing for application of seaweeds extract as nutraceutical.     

Effect of Micronizing Temperature on the Nutritive Value of Sorghum

Micronization is a process of heat treatment of grains using infrared radiation followed immediately by processing in an extruding-type roller mill. A laboratory model Pierce micronizer was used to process sorghum under three different temperatures: 102°, 250°, and 282°C. Sorghum processed at 250° had the highest starch availability value followed by sorghum processed at 282°C, sorghum processed at 102°, and raw sorghum. The extent of protein solubility was in decreasing order: raw, processed at 102°, processed at 250°, and processed at 282°. Increasing the temperature of the process destroyed more lysine. Animal study showed that a diet containing 15% protein from sorghum micronized at 250° and casein had a higher growth response than the diets containing raw sorghum or sorghums micronized at 102° or 282° C.     

Effect of thermosonication on quality improvement of tomato juice

Inactivation of pectinmethylesterase (PME) and polygalacturonase (PG) is required to minimize quality loss in tomato products. Tomato juice was subjected to thermosonication (TS) (24 kHz), at amplitudes of 25, 50 and 75 μm at 60, 65 and 70 °C or heat only treatments. The TS treatment at 60 °C, 65 °C and 70 °C for 41.8, 11.7 and 4.3 min exposure, respectively reduced PME activity by 90%. The heat only treatment at 60 °C, 65 °C and 70 °C for 90.1, 23.5 and 3.5 min, respectively inactivated PME by 90%. TS treatments with 25–75 μm amplitude had no significant impact on the inactivation efficiency between 60 and 70 °C. After TS the average particle size decreased noticeably (< 30 μm) and viscosity increased 2–4 fold, compared to the heat treated or untreated juice (180 μm)_. These results suggest that TS at 60 and 65 °C could be useful to obtain tomato juice with a low residual PME activity and high viscosity.Industrial relevanceThe processed tomato industry is constantly in search for potential alternative processes to conventional “cold break” and “hot break” treatments that could inactivate the pectic enzymes of importance. The findings of this study would help the industry to inactivate pectinmethylesterase (PME) enzyme at a lower temperature range and also achieve a higher viscosity due to the mechanical effects of thermosonication. Low temperature treatment would enable the retention of fresh-like properties of tomato juice. Based on the findings of this study, thermosonication could be considered as a potential alternative to conventional “cold break” and “hot break” treatments of tomato juice.     

Yields, Color, Moisture and Microbial Contents of Chicken Patties as Affected by Frying and Internal Temperatures

Frozen, raw, battered and breaded chicken patties were tempered to an internal temperature of 1.1 ± 0. 1°C. The patties were fried to three different internal temperatures (48.9°, 60.0° and 71.1°C) in each of three shortenings preheated to 168.3°, 179.4°, and 190.6°C. Yields and selected quality characteristics of the patties were measured. At the same internal cooking temperature, frying yield and moisture content of the patties were not different (P > 0.05). Higher frying temperature and longer frying time yielded lower Hunter “L” values and a tendency to produce higher Hunter “a” values. An interaction between frying temperature and internal temperature was significant for microbial counts. No difference (P > 0.05) in microbial count was observed when patties were fried to an internal temperature of 60.0° or 71.1°C.     

Simple test for differentiation between fresh pork and frozen/thawed pork

Enzyme profile of the exudates from fresh and frozen/thawed pork has been assayed by using a semi-quantitative method (APIZYM). Only three enzymes (esterase-lipase, ?-glucuronidase and α-glucosidase) showed significant differences (P < 0·01) between fresh and frozen/thawed pork. Different storage conditions were tested (freezing temperature: -10 to -60°C for 13 days and time of storage: 11 to 54 days at -18°C) but no significant differences were found among them. The APIZYM system would constitute a simple method for detecting frozen/thawed pork.     

Volatile distribution in garlic (Allium sativum L.) by solid phase microextraction (SPME) with different processing conditions

Treatments of autoclaving, high temperature aging (aged-black garlic), crushing, and roasting at 100, 150, and 200°C were applied to alter the volatile profiles of garlic (Allium sativum L.). Headspace volatiles in samples were analyzed by a solid phase microextraction (SPME)-GC/MS. Total peak areas of crushed-raw garlic were the highest and those of aged-black garlic clove were the lowest. Crushing effects were clearly observed in raw garlic, aged-black garlic, and roasted garlic at 200°C for 60 min. Sulfur-containing volatiles including diallyl disulfide and diallyl trisulfide were major volatiles. Generally, peak areas of diallyl disulfide decreased when garlic received autoclaving and roasting treatment while diallyl trisulfide and allyl methyl trisulfide increased during heat treatment compared to raw garlic. Roasting at 200°C for 60 min caused the formation of pyrazines greatly in garlic. Principal component analysis (PCA) for the volatile profiles by SPME-GC/MS could discriminate types of processed garlic successfully.     

Use of the APIZYM Testing System to Assess the State of Ripeness of Banana Fruit

The APIZYM activity profiles of untreated fruit ripening at 20°C and 85% RH were compared with those from fruits treated with Pro-long, a fruit coating material, and fruit stored under controlled atmosphere conditions (5% O₂, 95% N₂) at the same temperature and RH. Banana fruits coated with Pro-long or stored under CA conditions ripened more slowly than untreated fruits, and this was reflected in lower activity of some enzymes during the storage period in coated and CA-stored fruit. Reduced activity in these treatments was more noticeable at day 4 of storage than day 7; however, even at day 7, the activity of certain enzymes was still lower than in controls.     

High Pressure and Temperature Effects on Enzyme Inactivation in Strawberry and Orange Products

High hydrostatic pressure treatment (50-400 MPa) combined with heat treatment (20–60°C) effects on peroxidase (POD), polyphenoloxidase (PPO) and pectin methylesterase (PME) activities of fruit-derived products were studied. Assays were carried out on fresh orange juice and strawberry puree. Pressurization/depressurization treatments caused a significant loss of strawberry PPO (60%) up to 250 MPa and POD activity (25%) up to 230 MPa, while some activation was observed for treatments carried out in 250–400 MPa range for both enzymes. Optimal inactivation of POD was using 230 Mpa and 43°C in strawberry puree. Combinations of high pressure and temperature effectively reduced POD activity in orange juice (50%) to 35°C. The effects of high pressure and temperature on PME activity in orange juice were very similar to those for POD.     

Use of a spouted bed to improve the storage stability of wheat germ followed in paper and polyethlyene packages

Stabilization of wheat germ by heating in a spouted bed for 180–540 s with air at 140–200 °C was studied. The lipase activity decreased by 6–65%. Wheat germ processed at 200 °C for 360 s was ranked highest in sensory evaluation, described as having ‘a golden color’ and ‘nutty flavor’, and its lipoxygenase activity had decreased by 91.2%. This product and raw wheat germ were stored in paper, polyethylene and vacuum‐packed polyethylene pouches at 5 °C, room temperature (18–26 °C) and 40 °C, and the moisture contents, water activities, free fatty acid contents and peroxide values were followed for 20 weeks. The increases were faster in paper pouches than in the polyethylene ones; vacuum packaging in polyethylene did not bring about significant improvement. The peroxide values of raw samples exceeded 10 meq O₂ kg^?1 oil after 3–23 days while those of the processed samples stored at room temperature or 5 °C were still less than 10 after 20 weeks. The free fatty acid content and peroxide value changes were expressed by zero order kinetics, resulting in similar activation energies for the raw and processed samples. Copyright © 2005 Society of Chemical Industry     

Effect of steam cooking on the residual enzymatic activity of potatoes cv. Agria

BACKGROUND: The aim of this work was to study the influence of steam cooking on pectin methylesterase (PME) and endogenous α‐ and β‐amylase activities in different tissues (cortex and pith) of raw and heat‐treated potatoes cv. Agria. Three different cooking temperatures were chosen (55, 70 and 85 °C). For each cooking trial, time–temperature profiles were recorded and the degree of cooking was expressed in terms of cooking factor. RESULTS: Steam cooking contributed to significantly activate PME at 55 °C and to reduce its activity at the final processing temperature (85 °C), with the highest amount in the cortex (0.3745 ± 0.0007 µmol galacturonic acid (GA) g^?1 fresh weight (FW) min^?1) compared with the pith (0.2617 ± 0.0012 µmol GA g^?1 FW min^?1). The presence of heat‐labile and heat‐stable isoforms of PME in the considered potato tissues was also assumed. Heat treatment by steam resulted in a significant decrease in endogenous α‐ and β‐amylase activities in both tissues compared with the raw potato, though without complete deactivation. Starch‐degrading enzymes were also found to be differently distributed in the raw tuber. CONCLUSION: Steam cooking affected in different ways the assessed residual enzymatic activity in the considered tissues of potatoes cv. Agria. Further research is needed to confirm the results obtained. Copyright © 2011 Society of Chemical Industry     

Enzymatic Production of High-Protein Amaranth Flour and Carbohydrate Rich Fraction

The basic conditions of an enzymatic process to produce high-protein amaranth flour (HPAF) and carbohydrate rich fraction (CRF) from raw flour were determined. Commercial preparations of α-amylase and glucoamylase were used. Conditions for both enzymes were: 20% (w/v) slurries of gelatinized whole flour and 0.10% (v/w) enzyme; for amylase, pH 6.5, 70°C and 30 min liquefaction time; for glucoamylase, pH 4.5, 60°C and 60 min. The yield of HPAF was 38–39%. HPAF from both enzymes had 26–28% protein, 10–16% fat and 40–52% starch. Protein digestibility (76%) and reactive lysine (6.6–7.1 g/100g protein) of HPAF were comparable to raw flour. CRF had a 17–21 dextrose equivalent.     

ELISA Determination of Turkey Roll Endpoint Temperature: Effects of Formulation, Storage, and Processing

Effects of refrigerated and frozen storage, salt concentration, cooking schedule and product diameter were compared on determination of minimum endpoint cooking temperature of turkey breast rolls by measuring extractable protein (EP), lactate dehydrogenase (LDH) activity and LDH concentration by sandwich enzyme-linked immunosorbent assay. LDH concentration differed in rolls processed to 70.0°C and 71.1°C, whereas EP and LDH activity did not differ at these temperatures. Salt concentration, cooking schedule and product casing diameter did not markedly influence LDH concentration. LDH content of uncooked rolls decreased during frozen storage. A maximum concentration of 0.31 μg LDH/g meat indicated proper processing.     

Effects of Metmyoglobin Reducing Activity and Thermal Stability of NADH‐Dependent Reductase and Lactate Dehydrogenase on Premature Browning in Ground Beef

Premature browning is a condition wherein ground beef exhibits a well‐done appearance before reaching the USDA recommended internal cooked meat temperature of 71.1 °C; however, the mechanism is unclear. The objectives of this study were: (1) to determine the effects of packaging and temperature on metmyoglobin reducing activity (MRA) of cooked ground beef patties and (2) to assess the effects of temperature and pH on thermal stability of NADH‐dependent reductase, lactate dehydrogenase (LDH), and oxymyoglobin (OxyMb) in‐vitro. Beef patties (lean: fat = 85:15) were packaged in high‐oxygen modified atmosphere (HiOX‐MAP) or vacuum (VP) and cooked to either 65 or 71 °C. Internal meat color and MRA of both raw and cooked patties were determined. Purified NADH‐dependent reductase and LDH were used to determine the effects of pH and temperature on enzyme activity. MRA of cooked patties was temperature and packaging dependent (P < 0.05). Vacuum packaged patties cooked to 71 °C had greater (P < 0.05) MRA than HiOX‐MAP counterparts. Thermal stability of OxyMb, NADH‐dependent reductase, and LDH were different and pH‐dependent. LDH was able to generate NADH at 84 °C; whereas NADH‐dependent reductase was least stable to heat. The results suggest that patties have MRA at cooking temperatures, which can influence cooked meat color.     

Volatile compounds and changes in flavour‐related enzymes during cold storage of high‐intensity pulsed electric field‐ and heat‐processed tomato juices

BACKGROUND: The effects of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs, using 4 µs bipolar pulses at 100 Hz) on the production of volatile compounds and flavour‐related enzymes in tomato juice were investigated and compared with those of thermal processing (90 °C for 30 or 60 s). RESULTS: Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 °C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 °C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 °C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION: HIPEF‐treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat‐treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments. Copyright © 2010 Society of Chemical Industry     

Human Milk Banking: Influence of Different Pasteurization Temperatures on Levels of Protein Sulfur Amino Acids and Some Free Amino Acids

Human milk is frequently heat‐treated in hospitals, particularly milk that is banked, to destroy contaminating bacteria and viruses, but this treatment simultaneously reduces the content of some vitamins, enzymes, and immunological and nutritional factors. This study was performed to find the optimal conditions for heat treatment. The effects of 2 pasteurization temperatures on levels of protein sulfur amino acids (methionine, cystine) and some free amino acids (taurine, glutamine, glutamic acid) in light of the oxidative instability that occurs especially during thermal treatment were examined. These substances in raw human milk and in milk treated at 56.5 °C and 62.5 °C for 30 min were compared. Samples of mature human milk from all feeds over 24 h were obtained from 13 healthy well‐nourished mothers of term infants. Each sample was divided into 3 parts: raw, treated at 56.5 °C for 30 min, treated at 62.5 °C for 30 min. The results showed that the availability of sulfur amino acids and free taurine is the same after heat treatment, whereas milk processing increased positively the levels of free glutamic acid and glutamine, but there is significance only for glutamine. The mean quantities of considered amino acids were similar in milk treated at the recommended pasteurization temperature (30 min at 62.5 °C) and at 56.5 ° for 30 min.     

INACTIVATION of PROTEASES and LIPASE IN MILK IN THIN FILM SCRAPED SURFACE HEAT EXCHANGER

A cascade thin film scraped surface heat exchangers, having sterilizer, regenerator and cooler sections was designed and fabricated. It was employed for inactivation of thermostable proteases and lipases in milk. Buffalo milk was sterilized in the temperature range: 143–152°C for holding times of 0.75, 1.0 and 1.25 s. Samples collected aseptically were stored at 37°C to study the proteolytic and lypolytic activities. the study established that activity of enzymes in milk subjected to higher temperature was far less than that of milk processed at lower temperature for same holding time. the effect of longer holding times was similar.     

Effect of different treatments on the stability of lysozyme,lactoferrin and β‐lactoglobulin in donkey's milk

The aim of this study was to investigate the effects of freezing and heat treatments at different temperatures on the stability of the main whey proteins of donkey milk in comparison with those obtained from colostrum and raw milk. Samples subjected to heat treatment at 85 °C showed greater loss of stability, with levels decreasing by 60% and 87% for lysozyme and β‐lactoglobulin, respectively. Lactoferrin completely disappeared at heat treatments higher than 65 °C. Colostrum contained the highest lactoferrin and β‐lactoglobulin concentrations, however, lysozyme was found to be present at similar concentrations in colostrum, raw, frozen and heat‐treated milk at temperatures lower than 85 °C.