Modeling of Calcium Chloride and Pectin Methylesterase Prefreezing Treatments of Strawberries and Jams

ABSTRACT: :
Different calcium chloride (CaCl₂) and pectin methylesterase (PME) prefreezing treatments in a vacuum were used to clarify the most effective prefreezing factors for strawberries and traditional jams. Fractional factorial design and modeling were used. CaCl₂ had the greatest effect on the majority of the 15 studied responses ( p < 0.001). The pretreatment time should be short (about 5 to 10 min), the temperature low (less than 20 °C), the vacuum level high (pressure less than 10 kPa), the CaCl₂ concentration moderate (about 1%) and the dosage of PME comparatively low (about 50 to 100 nkat/g) in order to yield high quality frozen strawberries for jam making.     

Improved Firmness in Calcified Diced Tomatoes by Temperature Activation of Pectin Methylesterase

ABSTRACT: The effects of temperature and calcium on pectin methylesterase (PME) activity and texture in tomato pericarp material were examined. Heating thin slices of pericarp to temperatures between 50°C and 75°C led to the rapid evolution of methanol from the material, indicating an activation of PME. This activity was further stimulated when CaCl₂ (up to 2.0% w/v) was added. When applied to half-inch diced tomato pericarp, the same conditions that led to the activation of PME also improved firmness. Diced tomatoes treated for 5 min with 0.5% CaCl₂ at 70°C were 2.5 times firmer than diced tomatoes treated with CaCl₂ at room temperature. This improvement in texture by treating with CaCl₂ at elevated temperatures was only apparent when the tomatoes received a subsequent 100°C treatment. Heating tomatoes to 70°C either before or after the CaCl₂ treatment also improved firmness through a subsequent high-temperature treatment, but to a lesser extent than heating during the CaCl₂ treatment. These results are consistent with the model that heating to 70°C greatly increases PME activity, leading to extensive pectin de-esterification and increased calcium cross-linking of the pectins in the middle lamella. Production of thermally processed diced tomatoes with improved firmness should be possible by increasing the temperature during and after calcium treatment.     

Effects of Calcium Chloride-based Prefreezing Treatments on the Quality Factors of Strawberry Jams

ABSTRACT: Vitamin C contents of pretreated strawberries did not change during 2 mo of freezing, but after jam cooking and storage, the vitamin C contents of all the studied jams decreased dramatically. Jams made from strawberries treated with CaCl₂ and PME in a vacuum had the highest firmness compared to the reference or other pretreated jam strawberries (p < 0.05). According to sensory evaluation of the jams, different prefreezing treatments were shown to have a significant influence on the sensory attributes evaluated (p < 0.001), the only exception being the redness of color after 4 mo storage.     

Effect of Pectinmethylesterase Infusion Methods and Processing Techniques on Strawberry Firmness

Strawberry halves were pretreated with fungal pectinmethylesterase (PME) and calcium chloride using, respectively, passive osmotic infusion, vacuum‐assisted infusion, and pressure‐assisted infusion with the aim to improve the firmness. The vacuum‐assisted procedure was observed to be the only method able to accomplish an uptake of infusion solution and hence capable of improving the firmness of the strawberries. Significantly less firmness increase was realized when tomato PME was vacuum‐infused instead of fungal PME. Strawberry halves were pretreated by vacuum‐assisted infusion with fungal PME and calcium chloride and were subsequently subjected to thermal treatments at 60 °C and 80 °C and pressure treatments at about 400 MPa and 550 MPa. For all treatments studied, the pretreated sample was significantly firmer compared with the reference sample. For the thermal processes, the residual firmness relative to the initial value before treatment was depending on the temperature of the treatment and not on the pretreatment. However, vacuum‐assisted infusion of PME and calcium could limit the portion of firmness loss due to pressure treatment to 30% compared with 80% for non‐pretreated fruits.     

Freezing of strawberries by immersion in CaCl2 solutions

The present investigation studied the freezing of strawberries by immersion in CaCl₂ solutions, analysing drip loss, pectin content and the degree of esterification of the pectins, total and cell-wall bonded calcium contents, the ratio bonded calcium/total calcium, and textural parameters. In addition, the effect of immersion in pectin methylesterase (PME) solutions prior to immersion freezing (IF) was analysed. The firmness of thawed fruit decreased by approximately 74% with respect to fresh strawberries, and neither IF-CA (freezing by immersion in CaCl₂ solution) nor PME–IF-CA (immersion in PME solution + freezing by immersion in CaCl₂ solution) provided significant benefit in maintaining firmness when compared to slow freezing (SF). However, IF provided a significant benefit in reducing drip loss of thawed strawberries when compared to SF, but pre-treatment with PME did not provide any additional benefit.     

Enzyme infusion prior to thermal/high pressure processing of strawberries: Mechanistic insight into firmness evolution

Strawberries were infused with fungal pectinmethylesterase (PME) and calcium chloride, followed by a thermal (70 °C–0.1 MPa), a high pressure (25 °C–550 MPa) or a combined thermal-high pressure (70 °C–550 MPa) process. Macroscopic (firmness) and microscopic characteristics were assessed to evaluate the texture of the fruits. In order to interpret the texture changes, the chemical structure of pectin was investigated. Processing of strawberries caused a decrease in firmness, which was limited by infusion of PME and calcium chloride, although the extent of beneficial effects depended on the type of processing. PME was able to decrease the degree of methoxylation of pectin, which was accompanied by an increased crosslinking of the chains. During high pressure or combined thermal-high pressure processing, the degree of methoxylation of pectin in infused strawberries was even further decreased, probably due to a higher activity of the fungal PME under high pressure. In case of the high pressure process, this was reflected in a very firm texture. However, the combined thermal-high pressure process caused more severe tissue damage, in spite of the advantageous pectin properties.Industrial relevanceDuring high pressure processing of strawberries many nutritional and sensorial characteristics are quite well preserved. Unfortunately, texture of strawberries deteriorates during such processes. This paper provides mechanistic insight into how infusion of fungal pectinmethylesterase and calcium ions in strawberries can preserve the firmness of these fruits during high pressure processing.     

Texture of rehydrated dried bell peppers modified by low-temperature blanching and calcium addition

Diced green bell pepper was blanched twice, once at 51–79 °C for 19–61 min, and once at 95 °C for 3 min, and dried. The firmness of rehydrated samples was measured by puncture, and optimum conditions assessed by response surface methodology. The optimized model showed that, blanching at 65 °C for 49 min gave a 64% increase in puncture force over the control. The optimum temperature was used to evaluate the effect of adding CaCl₂. The dices were blanched twice, once at 65 °C for 3 min in either 0 or 4% CaCl₂, secondly in either 0 or 2% CaCl₂ solution at 95 °C for 3 min. In the second case the dices had been held at room temperature for 0–30 min before treatment. Adding CaCl₂ increased puncture force significantly ( P  ≤ 0.05). The best results, those which gave greatest firmness, were obtained by blanching at 65 °C for 3 min in 4% CaCl₂, holding for 16 min after blanching, followed by a secondary blanching at 95 °C in 2% CaCl₂.     

USE OF VACUUM IMPREGNATION TO DEVELOP HIGH QUALITY AND NUTRITIONALLY FORTIFIED FROZEN STRAWBERRIES

Strawberries (Totem) were vacuum impregnated (VI) before freezing with cryoprotectants of high fructose corn syrup (HFCS) or high methoxyl pectin (HMP) to improve quality, and with calcium and zinc salts to enhance the nutritional value of the product. The VI process consisted of a 15 min vacuum at 50 mm Hg and 30 min restoration at atmospheric pressure. VI pretreatment significantly increased the calcium and zinc content of frozen strawberries. VI with cryoprotectant improved the textural quality and reduced drip loss of frozen-thawed strawberries in comparison with untreated strawberries. Calcium in the VI solutions further increased the firmness of frozen-thawed strawberries, and zinc improved the color stability of the strawberries during the impregnation and freeze-thawing process.     

不同渗透加工方式对冷贮藏芒果粒的硬度影响

本研究以早熟台农芒果品种果粒加工为研究对象,运用质构仪检测超高压渗透加工对商业酶制剂前处理液浸渍冷储藏芒果粒的硬度,分析果胶甲酯酶、钙含量组成处理液和超高压相结合对芒果粒品质属性硬度的影响,且进行相关性分析;在不同压力渗透加工操作单元过程中探讨经预处理的低温储藏果粒硬度变化。主要研究结果如下:添加果胶酯酶有助于提升果粒的质构,有效降低了机械加工果粒硬度的损失。芒果粒经过果胶甲酯酶PME和0.5%(m/m)CaCl2·2H2O组成预处理液及0.09 MPa,15 min真空协助渗透,结合450MPa,15 min超高压压力渗透,经TPA检测真空协助超高压渗透加工预处理组的果粒硬度比水渗透组的变化显著增加,冷藏果粒硬度从水渗透组的358.5g上升至预处理组的1111.7g,预处理组果粒硬度比水渗透组提高83.7%,且前处理技术果粒硬度比鲜果组提高18%,得到果粒的质构特性最好,有助于产品品质的提升。     

Factors Determining Yield Stress and Overrun of Whey Protein Foams

ABSTRACT: Foams were formed by whipping whey protein solutions (15% w/v protein) containing NaCl, CaCl₂, lactose, or glycine. Foam overrun and yield stress were determined. Foams made from whey protein ingredients have greater overrun and yield stress if the concentration of β-lactoglobulin is high relative to a-lactalbumin. The presence of 0.4 M CaCl₂ in the foaming solution increases overrun and yield stress for β-lactoglobulin and a-lactalbumin. The high yield stress of β-lactoglobulin and a-lactalbumin foams made from solutions containing CaCl₂ suggests that CaCl₂ is altering rheological properties of the interfacial protein film and/or contributing to protein aggregation or network formation in the lamellae.     

MICROWAVE BLANCHING OF CUBED POTATOES

Cubed potatoes cv. Primura were blanched by microwaves in water, NaCl solution, CaCl₂ solution and NaCl-CaCl₂ solution at selected powers and times. Mass and water gain/loss, firmness, starch gelatinization, color and polyphenoloxidase activity were evaluated. The results showed that all the blanching treatments induced a weight loss even if it was caused by a combined loss of water and dry matter in potatoes blanched in the saline solutions whereas it was a balance between water gain and dry matter loss in potatoes blanched in water. Firmness was affected in a negative way especially by the treatment time. Potatoes blanched in NaCl-CaCl₂ showed the highest firmness retention, whereas potatoes blanched in NaCl were less consistent. Treatment time and microwave power contributed in the same way to the starch gelatinization. It was necessary to prolong the time of treatment to 3–5 min and apply high power to inactivate polyphenoloxidase.     

Effect of the addition of trisodium citrate and calcium chloride during salting on the rheological and textural properties of Cheddar-style cheese during ripening

The effect of addition of trisodium citrate (TSC) and calcium chloride (CaCl₂) on the textural and rheological properties of Cheddar-style cheese was investigated. Cheese curds were salted (2.5%) with NaCl (control) or NaCl supplemented with either TSC or CaCl₂ with a constant ionic strength. Casein-bound calcium phosphate decreased upon addition of TSC and increased upon addition of CaCl₂. Addition of CaCl₂ resulted in increased hardness. Addition of TSC resulted in reduced hardness but more elastic cheeses at high temperatures. The addition of TSC or CaCl₂ at salting had a significant effect on cheese rheology and texture.     

Effects of Ripeness Stages on the Storage Atmosphere, Color, and Textural Properties of Minimally Processed Apple Slices

ABSTRACT: Fruit maturity is a determinative factor in maintaining the original color and, to a greater extent, the texture of minimally processed fresh-cut apple slices. Mature-green apples (because of their lower respiration and ethanol formation) were the most suitable to process for extending post-cutting-quality shelf life. Sliced apples processed at an earlier stage of ripeness, but dipped in a solution of ascorbic acid (C₆H₈O₆) and calcium chloride (CaCl₂) and stored under 100% N₂, preserved their original color with minor changes. However, these processing and packaging treatments could not effectively prevent the apple slices from softening, and apple flesh underwent a progressive loss of firmness from 8.0 to 4.8 N.     

Formation of Soy Protein Isolate Cold-set Gels: Protein and Salt Effects

ABSTRACT: The influence of protein and calcium concentration on soy protein cold-set gel formation and rheology has been investigated. Cold-set gels can be formed at soy protein concentrations from 6% to 9% and calcium concentrations from 10 to 20 mM. Gel properties can be modulated by changing the protein and/or CaCl₂ concentrations. An increase in CaCl₂ concentration from 10 to 20 mM increased gel opacity while an increase in protein concentration from 6% to 9% decreased opacity. Water-holding capacity improved with increasing protein concentration and decreasing CaCl₂ concentration. The elastic modulus (G') increased with protein and calcium chloride concentrations. Microscopy revealed an increase in the diameters of aggregates and pores as CaCl₂ concentration increased and as protein concentration decreased. Cold-set gels with a broad range of characteristics can be obtained from soy protein.     

Ultrastructural and Changes in Pectin Composition of Sweet Cherry from the Application of Prefreezing Treatments

ABSTRACT: Thermal and calcium pretreatments applied to preserve the sweet cherry texture by the freezing/thawing process produced biochemical changes in the pectic substances and ultrastructural alterations to the cells and tissues, which were visible under scanning electron microscopy. Partial dehydration of the epidermic tissue caused by calcium (100 m M CaCl₂) and thermal (50 °C/10 min) pretreatment attenuated the surface damage produced by freezing. However, pretreatment at 70 °C/2 min caused partial destruction of the epidermic tissue and plasmolysis of the parenchymatic cells. After freezing, the cell walls in the parenchymatic tissue of the fruits pretreated with 100 m M CaCl₂ exhibited swelling as a result of gelling of the cell-wall pectic material. Thermal pretreatments increased the ethylenediaminetetraacetic acid (EDTA)-soluble pectin fraction and reduced the degree of pectin esterification. Thermal treatments at 70 °C, without immersion in calcium, reduced the water- and pectinase-soluble pectin fractions, whereas immersion in calcium prevented depolymerization of these fractions. Immersion in 100 m M CaCl₂ increased the water-soluble pectin fraction.     

Effect of Preprocessing Treatments on the Firmness and Quality Characteristics of Whole and Sliced Strawberries After Freezing and Thermal Processing

Procedures designed to improve fruit firmness of overripe strawberry fruit originally designated for the fresh market were investigated. The firmness of ‘Cardinal’ strawberries was increased by soaking or vacuum infiltrating in 1 or 2% Ca lactate solutions. Calcium lactate was more effective in firming sliced than whole fruit. Thermally processed fruit benefited more from calcium absorption than did the frozen, thawed fruit. Whole fruit firmness was increased by the vacuum infiltration of Ca lactate. There was little increase in firmness of the sliced fruit when the calcium was vacuum infiltrated as compared to a soak treatment with no vacuum. There were slight but significant differences among treatments on all quality attributes tested. However, these quality differences would have no commercial importance.     

Postmortem Calcium Chloride Injection Alters Ultrastructure and Improves Tenderness of Mature Chinese Yellow Cattle Longissimus Muscle

ABSTRACT: This study was conducted to test the hypothesis that postmortem calcium injection could activate the calpain system in mature Chinese Yellow Cattle muscle, thereby promoting meat tenderization through disruption of the myofibril structure during aging. A 10% (w/w) injection of CaCl₂ (300 m M ) solution lowered the Warner-Bratzler shear values of longissimus muscle by more than 30% ( P < 0.05), even with only 24 h postmortem storage when compared with noninjected or water-injected controls. The accelerated meat tenderization by the Ca²⁺ treatment paralleled the changes in myofibril fragmentation index and fracture of the myofibril ultrastructure throughout the sarcomere but most notably around the I-bands and the Z-disks. Injection of ZnCl₂ (50 m M ) largely inhibited these proteolytic changes. The colorimetric L * and a * values were not affected by CaCl₂ nor by ZnCl₂ injection. The results suggest that postmortem CaCl₂ injection can be used to help resolve the toughness problem of mature Chinese Yellow Cattle meat and shorten the aging time required to achieve adequate tenderness.     

Effects of Vacuum Impregnation with Calcium Ascorbate and Disodium Stannous Citrate on Chinese Red Bayberry

This study aimed to improve the shelf life of Chinese red bayberries using vacuum impregnation. Vacuum pressure of 5 kPa for 15 min, atmospheric pressure for 10 min, an impregnation temperature of 20 °C, alone or in combination with isotonic sucrose solution, 1% food-grade disodium stannous citrate (DSC) and 2% food-grade calcium ascorbate were used for vacuum impregnation. Quality parameters, including firmness, weight loss, decay rate, microbial counts and polyphenol oxidase (PPO) and peroxidase (POD) activities, of red bayberries were studied at 2 °C for 10 days. The monosaccharide components, chemical structures and nanostructure properties of chelate-soluble pectin (CSP) were further studied using high-performance liquid chromatography, Fourier transform infrared spectroscopy and atomic force microscopy (AFM). The results indicated that vacuum impregnation with calcium ascorbate alone or calcium ascorbate combined with DSC showed significant effects on inhibiting the decrease of firmness (4–10 days), the increase of weight loss (2–10 days), decay rate (4–10 days) and microbial growth (2–10 days). In addition, vacuum impregnation with single calcium ascorbate or DSC or their combination significantly inhibited the increase of colour difference from day 6 to day 10 during storage, which was better than atmospheric impregnation. Furthermore, vacuum impregnation with DSC and calcium ascorbate had the best effect on sensory attributes. The nanostructure analysis by AFM showed CSP of large width and length when calcium ascorbate was impregnated, suggesting that vacuum impregnated with 2% calcium ascorbate inhibited the degradation and dissociation of CSP, although these fruits showed more branching of rhamnogalacturonan and a small change in chemical structure.     

APPLICATION OF LOW TEMPERATURE HEAT TREATMENTS BEFORE RETORTING IMPROVES THE QUALITY OF CANNED POTATOES

Low temperature heat treatments applied to potatoes (cv Atlantic, Snowden, and Pike) prior to retorting were evaluated for their effect on sloughing in canned potatoes. Blanching in water for 30 min at 60 - 77C before retorting decreased potato breakage, brine turbidity, and brine soluble solids without adversely affecting firmness or color. Low temperature blanching was only effective when potatoes were retorted in CaCl₂ (0.1 %) brine solutions. Sloughing was also decreased by a hot-fill and hold process that utilized brine fill temperatures of 77 − 93C followed by a 30 min hold in CaCl₂ (0.1 %) brine before commercial sterilization. The hot-fill and hold method for control of sloughing in canned potatoes is an improvement over current methods because it eliminates the need for a blanching step and requires only minimal changes in equipment or product flow.     

Calcium Chloride Added to Irrigation Water of Mushrooms (Agaricus Bisporus) Reduces Postharvest Browning

The influence of 0.3% CaCl₂ added to irrigation water on mushroom tyrosinase activity and postharvest browning was examined. Calcium concentration of mushrooms was significantly increased with the addition CaCl₂ to irrigation water but had no effect on inherent tyrosinase activity but reduced postharvest browning. The CaCl₂ had even more pronounced improvement in shelf life as indicated by reduced browning following a standard bruising treatment. Transmission electron micrographs indicate that increased levels of calcium in mushrooms irrigated with CaCl₂may have decreased browning by increasing vacuolar membrane integrity; thereby reducing the opportunity for tyrosinase to react with its substrates.