Thermal and Calcium Pretreatment Affects Texture, Pectinesterase and Pectic Substances of Frozen Sweet Cherries

Freezing causes loss of turgidity and firmness in sweet cherries. Thermal pretreatment at 50°C for 10 min followed by immersion in 100 mM CaCl₂ and thermal pretreatment at 70°C/2 min with or without immersion in 100 mM CaCl₂ prevented freezing-induced loss of firmness. Thermal pretreatments increased the pectin fraction soluble in EDTA, reduced the degree of pectin esterification, and increased both the concentration of divalent cations in the cell wall and the pectinesterase activity bounded to the cell wall. Immersion in CaCl₂ increased the concentration of Ca²⁺ cations in the cell wall and enhanced the effect of thermal pretreatments on pectinesterase activity.     

Effect of Fertilization, Postharvest Handling and Blanching Temperature on the Drained Weight of Canned Summer Squash

There was no apparent effect on drained weight or firmness when three rates of calcium fertilization and two rates of potassium fertilization were applied to a test planting from which two harvests of raw summer squash were canned. However, high Ca (L₂) decreased dry matter and increased structural carbohydrates and tissue Ca in the canned product. Precooling increased drained weight and dry matter, but drastically reduced firmness of the canned product. Noncooled canned squash had lower drained weights and pH, but greater firmness and higher water soluble pectin and cellulose content. Blanching at 99°C increased drained weight; blanching at 88°C decreased drained weight, but increased calgonsoluble pectin content.     

Snap Bean Texture Softening and Pectin Solubilization Caused by the Presence of Salt during Cooking

Special procedures were used to separate the effects on softening and pectin solubilization of the presence of salt during cooking from the effects of salt apart from cooking. The effects of the presence of salt during cooking, calculated with respect to corresponding distilled water cooked beans, were greater with processing conditions of lower blanch temperature and shorter cook times, consequently they were greater with higher canned bean firmness and lower liquor pectin. Neither softening nor pectin solubilization had a significant relation to the reduction in pH induced by NaCl. The softening due to salts was seen with NaCl, KCl, and, to a lesser extent, with CaCl₂, and it may be the result of accelerated degradation of pectins.     

A modified laboratory canning protocol for quality evaluation of dry bean (Phaseolus vulgaris L)

The effects of calcium (Ca²⁺) level in the soak water, blanch water and brine, blanching temperature, and total seed solids on dry bean canning quality were investigated to optimise a laboratory canning protocol. A linear increase in the Ca²⁺ level of soak water, blanch water and brine resulted in a linear decrease in hydration coefficient and percent washed drained weight but a linear increase in texture. Low Ca²⁺ level (10 mg kg⁻¹) reduced the hydration time for dry bean seed from 14 to 1 h. Blanching temperatures of 50, 70 and 88 °C had non‐significant effects on canning quality traits. Blanching for 30 min at 70 °C for black bean or at 88 °C for navy bean and pinto bean resulted in percent washed drained weight ≥ 60, as required by the Canada Agricultural Products Standards Act. Seed solids levels of 95–97 g per 300 × 407 (14 fl oz) can were sufficient to attain a percent washed drained weight of 60. It was confirmed that the thermal processing conditions (115.6 °C retort temperature, 45 min) used in this study were sufficient to achieve commercial sterility. The optimised lab protocol for evaluation of the canning quality of dry bean breeding lines is as follows. Seed containing 95 g of solids for pinto bean, 96 g for navy bean and 97 g for black bean is soaked in water for 30 min at 20 °C and blanched for 30 min at 70 °C for black bean and 88 °C for navy bean and pinto bean in water containing 10 mg kg⁻¹ of Ca²⁺. The seed is then transferred to a 300 × 407 can, filled with brine containing 10 mg kg⁻¹ of Ca²⁺, 1.3% (w/v) of NaCl and 1.6% (w/v) of sugar. The can is then sealed, processed in steam at 115.6 °C for 45 min and cooled at 20 °C for 20 min. Cans are stored for at least 2 weeks prior to quality evaluation of the canned product. Canning of dry bean seed according to this protocol results in precise estimation of canning quality traits, particularly percent washed drained weight. © 2000 Society of Chemical Industry     

Effect of Blanch Temperature on Kinetics of Thermal Softening of Carrots and Green Beans

Cut green beans and diced carrots were blanched at 100°C and 74°C then canned and processed for 5 min to 300 min at 100°C. In every case the rate of thermal softening was consistent with the two substrate first-order kinetic theory of thermal softening of vegetable tissue. The low temperature blanch caused some changes in the apparent firstorder rate constants for both substrates, but the major difference was a much higher intercept of the extrapolated substrate S_S line on the firmness axis. We define S_S at zero process time as the “thermal firmness value” because it is a good indicator of what the firmness of the vegetable will be after canning.     

Low Temperature Blanching Effects on Chemistry, Firmness and Structure of Canned Green Beans and Carrots

Green beans and carrots were canned using extended blanching at 64–65°C and added calcium and/or acid. Firmer products resulted from all treatments but lowered pH was most effective. Blanched green beans were firmer with lower pectin esterification, indicating pectin methyl esterase activity. Green beans and carrots treated with calcium and/or acid and then cooked were firmer than controls. Acid exhibited a firming effect, perhaps by loosening tissue, while calcium reduced the influence of heat. Instrumental bioyield values correlated with sensory results of canned green beans; bioyield may result from a scleriformic layer. Microscopy showed firmer beans had intact middle lamellae while softer samples contained separated cells. These data suggest that the treatments rendered pectates in the middle lamella less heat labile.     

The effect of processing on the texture of canned mung bean (Phaseolus aureus) shoots

The effect of various processing regimes on the pectic substances and the final texture of canned mung bean shoots has been studied. A blanching temperature of 75°C for 30 s was optimal in activating the native pectinesterase of the shoots and a holding temperature of 55°C for an optimal 30 min led to maximal deesterification of pectin. This treatment resulted in a canned product that was superior to a sample blanched at 100°C.; the addition of calcium ions did not improve the product.     

INFLUENCE OF VARIOUS SALTS IN THE COOKING WATER ON PECTIN LOSSES AND COOKED TEXTURE OF COWPEAS (VIGNA UNGUICULATA)

The effects of processing with solutions of calcium chloride, magnesium chloride, sodium bicarbonate and a local tenderizer known as ‘Kanwa’ (sodium sesquicarbonate) on pectin losses and cooked texture of cowpea seeds were investigated. For comparison, the cowpeas were processed in double distilled water and a local tap water. Analysis included total pectin, calcium and magnesium content, leached solids, texture and water absorption. The results show that CaCl₂, MgCl₂ and the local tap water increased firmness, Ca and Mg content in the cooked beans compared to distilled water; however, water absorption, leached solids and pectin solubilization were decreased by these salts. Kanwa and NaHCO₃ increased water absorption, leached solids and softness in the cooked beans and also increased pectin solubilization but decreased Ca and Mg when compared to distilled water or the other salts. These changes are discussed with respect to the effects of divalent and monovalent cations on the texture of the bean tissue.     

Processing Factors Influencing Splitting and Other Quality Characteristics of Canned Kidney Beans

Single factor changes from a standard canning process indicated that significant reductions in splitting resulted from higher soak Ca concentrations, higher soak temperatures, higher brine Ca concentrations, and shorter cooking times. Splitting in canned kidney beans was markedly reduced by soaking beans before cooking at temperatures of 66–71°C in solutions containing 150–350 ppm CaCl₂. Treatments giving lower gain in weight during soaking led to less splitting. Lower splitting was associated with lower drained weight and firmer cooked beans.     

Effects of Vacuum Hydration on the Incidence of Splits in Canned Kidney Beans (Phaseolus vulgaris)

Dry red kidney beans were canned using two different pretreatments: soaking for 12 hr at 20°C, and vacuum hydration for 5 min followed by soaking for 2 hr at temperatures from 45-59.1°C. Samples were then packed, processed to commercial sterility, and tested for percentage of split beans after processing. Vacuum hydration pretreatments greatly decreased the incidence and severity of splitting in the canned product and accelerated water uptake while retaining the same moisture content after soaking as the conventional soak treatment. Vacuum-hydrated beans gained less moisture during retorting than conventionally treated samples.     

Potential use of fruit waste containing in vivo De-esterified pectin as a thickener in canned products

Orange peel and tomato skins were treated with sodium carbonate to pH 8.5 to cause in vivo pectin de-esterification principally by pectinesterase action. The resulting material was dried and powdered and then evaluated for thickening properties in canned systems. It was found that after autoclaving for 75 min at 121.1 °C in a rotating retort in the presence of guar gum, sodium tripolyphosphate and calcium sulphate dihydrate, high post process viscosities could be obtained when orange peel was included at a concentration of 0.5% provided the pectin degree of esterification was reduced below 20% and the intrinsic viscosity of the pectin measured after extraction was above 3 dl g^?1. Thickening was also obtained with tomato skins providing these two conditions were fulfilled. The dependence of viscosity on the calcium level and the thixotropic nature of the solutions obtained after processing, demonstrate that a calcium pectate gel can be formed even after severe heat treatment at a neutral pH. It is suggested that fruit and vegetable material containing in vivo deesterified pectin may be of value as a thickener in canned foods.     

Thermal Effects on Net Protein Ratio of Red Kidney Beans (Phaseolus vulgaris L)

Net protein ratio (NPR), predicted-protein efficiency ratio (P-PER), relative NPR (RNPR), and corrected RNPR (CRNPR) of thermally processed red kidney beans were estimated in rats and compared to in vitro protein digestibility-corrected amino acid score (AAS_IVDP), and computed-protein efficiency ratio (C-PER). Thermal processing had a significant effect on protein intake, NPR, P-PER and CRNPR values of beans. Changes in protein intake suggest that heat processing had an effect on the palatability of the beans. Home-cooked beans and commercially canned beans had higher NPR values than beans autoclaved at 128°C for 20 min, while beans autoclaved at 121°C for 10–90 min had intermediate values. High correlation coefficients between P-PER and C-PER, CRNPR and C-PER, and CRNPR and AAS_IVDP (r=0·990, 0·992 and 0·960, respectively, P<0·001) were observed.     

Vitamin Retention, Color and Texture in Thermally Processed Green Beans and Royal Ann Cherries Packed in Pouches and Cans

Thiamin (B-1) ascorbic acid (AA) and vitamin B-6 (B-6) were determined in pouched and canned green beans immediately after processing and after storage at 24–26°C or 38°C. AA and B-6 were also determined in pouched and canned cherries before and after storage at 24–26°C. There was significantly more B-1 and AA in drained pouched green beans, and more AA in drained pouched cherries than in canned ones. B-6 values in the solids of the pouched and canned products were not significantly different. These three vitamins were significantly reduced in drained pouched and canned green beans after storage at 38°C. B-6 was significantly reduced in the stored cherries. Compared to canned, the pouched products were brighter and firmer in texture.     

Effect of Heat Processing on Hemagglutinin Activity in Red Kidney Beans

The effect of temperature in destroying the hemagglutinin (lectin) activity in red kidney beans has been determined. Heating presoaked beans at 100°C for 15 min or at 80°C for 2 hr, or pressure cooking (15 psi) foi 45 min without presoaking, decreased the hemagglutinin activity to below detectable levels. At 65°C, no significant decrease was observed even after 12 hr heat treatment. Commercially canned beans have lectin levels similar to beans pressure cooked for 30 min.     

Optimization of a Diced Tomato Calcification Process

The effect of calcium concentration (0.05-1.45% CaCl₂), temperature of dipping solution (35-65°C), and contact time (0.5-3.5 min) on calcium uptake, firmness and pH of diced tomatoes was evaluated during a calcification process using response surface methods. Temperature had no significant effect on the process. Application of graphical optimization techniques revealed that processing in a solution of relatively low calcium concentration (?0.43% CaCl₂) at ambient temperature (? 35°C) for about 3.5 min would yield a product with Ca⁺⁺ content below the legal limit (<800 μ-g/g), improved firmness (shear force value > 20 N/g), and with pH low enough (<3.95) to eliminate any requirement for acidification treatment.     

Dehydrated Precooked Pinto Bean Quality as Affected by Cultivar and Coating Biopolymers

The relationship of cultivars and coating treatment to quality of precooked dehydrated pinto beans was investigated. The pinto cultivars, studied were Fiesta, Othello, and Topaz, and 12 types of biopolymers, including modified starches, dextrins, maltodextrins, and alginate, were used as coating agents. Beans were blanched, soaked, steam cooked, coated by dipping in biopolymer solutions at 70°C and dried in a convection oven. Eight biopolymers effectively reduced splitting of beans without detrimental effects on rehydration, firmness, or color. Cultivar had a strong effect on wholeness of bean products and Fiesta was best for dehydration. Residual trypsin inhibitor activity of precooked pinto beans was ～5%.     

Firmness and Cell Wall Characteristics of Pasteurized Jalapeño Pepper Rings as Affected by Preheating and Storage

Changes in cell wall pectic substances, degree of pectin methylation, bound calcium and firmness were determined in preheated and nonpreheated fresh pack jalapeño pepper rings stored for 5 mo. Pepper rings preheated for 60 min at 50°C in a brine solution (8% NaCl and 0.2% CaCl₂, were firmer, had more nonextrctable pectins (NXP), more bound calcium, less water-soluble and chelator-soluble pectins (CSP), and less pectin methylation than nonpreheated pepper rings. The greater formation and maintenance of nonextractable pectins, which resisted acid hydrolysis during pasteurization and storage is probably an important factor in firming.     

Influence of pulsed electric fields (PEF) with calcium addition on the texture profile of cooked black beans (Phaseolus vulgaris) and their particle breakdown during in vivo oral processing

This study investigated the use of pulsed electric fields/PEF (electric field strengths 1–2 kV/cm, specific energy 9–127 kJ/kg) to facilitate calcium uptake into black beans in preserving their hardness from thermal degradation during subsequent cooking (1 h, 70–90 °C). Increasing specific energy reduced CaCl₂ concentration in PEF processing media to 100 ppm to improve the hardness of cooked black beans. Those pre-treated at lower energy required min. 300 ppm CaCl₂. Cooked black beans with PEF-pretreatment shared similar hardness as without PEF but unexpectedly chewier (18–43% more energy to disintegrate the beans). In vivo mastication study showed particle size at 18 and 24 s of mastication was significantly different (p < 0.05) wherein “PEF without CaCl₂” had the smallest particles compared to “No PEF with CaCl₂” and “PEF with CaCl₂”. The outer seed coats of PEF-pretreated beans were easily masticated to smaller and consistent particles. This implies that PEF improved particle breakdown during mastication.     

Effect of Vacuum Impregnation Combined with Calcium Lactate on the Firmness and Polysaccharide Morphology of Kyoho Grapes (<Emphasis Type="Italic">Vitis vinifera</Emphasis> x <Emphasis Type="Italic">V. labrusca</Emphasis>)

The effects of vacuum impregnation (VI) with 2% calcium lactate treatment on the VI properties (obtained from hydrodynamic mechanism and deformation–relaxation phenomena models), firmness, and pectin of Kyoho grapes were investigated. Fruit pectin was analysed by atomic force microscopy (AFM). VI was applied for 10–35 min at 25–45 °C and 5 kPa. The maximum values of effective porosity, ε_e (0.606%), and volume fraction, X (0.588%), occurred at 35 °C when the VI time was 15 min. No change was observed in the volumetric deformation (γ ≈ 0) of the grapes after the impregnation. The firmness significantly increased at 35 °C VI (from 12.93 to 14.47 N). According to the AFM results, calcium mainly inhibited the degradation of chelate-soluble pectin and sodium carbonate-soluble pectin short branches during the VI. Under the studied conditions, the validity of VI to incorporate calcium into fruit to improve the quality of grapes was verified, and a final corresponding product was obtained by VI.     

Firmness Retention in Pickled Peppers as Affected by Calcium Chloride, Acetic Acid, and Pasteurization

Critical factors influencing firmness retention in pickled peppers were studied. The addition of CaCl, (0.2%, w/v, optimum) to whole, pickled‘Red Cherry’peppers increased firmness retention as determined by a puncture test using an Instron Universal Testing Machine. Pasteurization reduced firmness in the absence, but not in the presence, of added CaCl₂. CaCl₂ significantly (P ≤0.01) reduced softening during storage of‘Red Cherry’peppers at higher temperatures (36.7, 46.7°C), and resulted in a slight increase in firmness at 26.7°C. CaCI₂ did not significantly (P≥ 0.05) improve firmness retention in‘Jala-peno’peppers, but resulted in greater uniformity of firmness. CaCI, also improved firmness retention in pickled cucumbers. Firmness of unpasteurized peppers and cucumbers was not influenced significantly (P ≥0.05) by acetic acid concentrations of 2, 3 or 4%.