THE EFFECT OF COATINGS AND PROCESSING METHODS ON DEHYDRATED PRECOOKED WHOLE PINTO BEANS QUALITY1

Splitting is a major problem in preparing dehydrated precooked beans. To reduce splitting and improve the product quality of precooked pinto beans, three coating treatments and two processing methods were investigated. Beans were blanched, soaked, steam precooked, coated by dipping in a biopolymer solution, and dehydrated in an air-circulating dryer. Coating beans in a 20% dextrin solution (Lo-Dex 5, M100, or K4484) reduced 43–85% of butterflying (severe splitting) of beans. Steam precooking at 121C/30 min with soaking at 22C/12 h yielded less butterflying than steam precooking at 100C/1 h with soaking at 30C/2 h and 82 C/1 h after coating and dehydration (?3% vs 8%). The former resulted in lower firmness after precooking and rehydration of dehydrated beans, whereas the latter gave beans a more mealy texture and better appearance. The rehydration time of dehydrated precooked beans in boiling water to produce an acceptable firmness was 6–9 min, depending on the processing methods. Coating resulted in darker color and slower rehydration of dehydrated beans.     

EVALUATION OF EFFECTS OF SOAKING AND PRECOOKING CONDITIONS ON THE QUALITY OF PRECOOKED DEHYDRATED PEA, LENTIL AND CHICKPEA PRODUCTS

Peas, lentils and chickpeas were blanched and soaked in water, then cooked with four different cooking methods and dehydrated in a convection tray dehydrator. Color, splitting and butterflying rate; firmness; and rehydration rate were evaluated. Dehydrated yellow and green peas produced by soaking at 22C for 9 h and 82C for 4 h in 0.07% NaHCO₃ solution, and followed by precooking at 110C for 10 min had the best quality with respect to firmness, splitting and butterflying rate. Dehydrated chickpeas produced by soaking at 22C for 9 h and 82C for 3 h in 0.07% NaHCO₃ solution, and followed by precooking at 110C for 10 min had the best quality. Dehydrated lentils produced by soaking at 22C for 2 h and 82C for 20 min in 0.07% NaHCO₃ solution, and followed by precooking at 106C for 10 min had the best quality.

PRACTICAL APPLICATIONS

Traditionally, soaking and cooking of peas, lentils and chickpeas (PLCs) takes one a long time. It is desirable to manufacture dehydrated precooked PLCs to provide convenience for the users. The objective of this study was to investigate the quality of precooked dehydrated PLCs as affected by processing. The fundamental cooking characteristics of PLCs obtained in this study are very useful for the food industry.     

Processing of cauliflower by ohmic heating: influence of precooking on firmness

The feasibility of processing cauliflower by ohmic heating was investigated. Firstly, cauliflower florets were precooked in tap water at low temperatures (40–70 °C) for 0 to 60 min. A control sample was cooked at 95 °C for 5 min. No significant textural differences were found between samples treated at 40 or 50 °C and fresh samples, but the firmness of samples cooked above 60 °C decreased. The effect of precooking time was not found to be significant. Secondly, low temperature precooking was performed in salted water for 30 min and followed by ohmic heating (holding time 30 s at 135 °C). After ohmic heating, florets pretreated at low temperatures were firmer than control samples. The firmness of florets precooked at 40 °C or 50 °C was considerably increased (>300%) compared to those precooked at 95 °C. Low-temperature precooking increased the firmness of cauliflower subjected to ohmic heating. The experimental results show that ohmic heating combined with low-temperature precooking in saline solutions offers a viable solution to high temperature/short time sterilisation of cauliflower florets. © 1999 Society of Chemical Industry     

Rapid Rehydration Methods for Dried Beans

Rapid methods of rehydrating dried kidney, pinto or navy beans by soaking at 82°C or 93°C for 5, 10 or 30 min were compared to standard 18 hr soaking at ambient temperature. Canned beans processed 21 min at 121°C had higher drained weights and softer texture with fewer split beans than those processed 41 min at 116°C. Kidney, pinto and navy beans soaked 30 min at 82°C had higher drained weight than those soaked 30 min at 93°C. Hydration coefficient (2.07) of controls (18-hr soak) and beans soaked 82°C (1.94) or 93°C for 30 min were not different. Pre soaking 30 min at 82°C provided adequate rehydration prior to canning.     

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.     

Effect of Storage Conditions and Chemical Treatments on Firmness, in Vitro Protein Digestibility, Condensed Tannins, Phytic Acid and Divalent Cations of Cooked Black Beans (Phaseolus vulgaris)

Black beans stored at 30° or 40°C and 80% relative humidity showed marked increases in firmness and decreases in in vitro digestibility of proteins. Changes in these properties were small when beans were stored at 5°C and 50% relative humidity. The adverse effects of poor storage conditions could be practically eliminated by soaking beans in salt solutions instead of water. The changes in firmness and digestibility were accompanied by changes in the detectable concentrations of tannins and phytates. Protein digestibility appears to be reduced by interactions between protein and tannins, especially high molecular weight tannins. Concentration of these tannins is affected by poly-phenol oxidase activity. Firmness increased and protein digestibility decreased as the phytic acid content decreased.     

Effect of temperature, pressure and calcium soaking pre-treatments and pressure shift freezing on the texture and texture evolution of frozen green bell peppers (Capsicum annuum)

The firmness of green bell pepper (Capsicum annuum) was studied under different processing conditions. Thermal texture degradation kinetics of pepper tissue between 75 and 95 °C could be accurately described by a fractional conversion model. The firmness of pre-processed pepper increased when the samples were submitted to several heat, pressure, and combinations of heat/pressure and calcium soaking pre-treatments. Pre-heating at 55 °C during 60 min and mild heat/high-pressure treatments (200 MPa at 25 °C, 15 min) yielded the best results, which were further improved when combined with calcium soaking. These pre-treatments significantly slowed down thermal texture degradation of pepper at 90 °C, a typical temperature used for pepper blanching prior to freezing. The above-mentioned pre-treated samples showed a significant reduction in firmness when frozen by regular freezing at 0.1 MPa. The same samples showed no changes in firmness when frozen by high-pressure shift freezing at 200 MPa. When freezing was carried out by high-pressure shift and after frozen storage (−18 °C) for 2.5 months, pressure pre-treated pepper showed a better retention of texture than thermal pre-treated pepper.     

Effect of Temperature on the Serum Viscosity of Tomato Juice

Tomato juice was canned and exposed to processing temperatures of 82°C., 102°C and 112°C. Serum viscosity was measured after 30, 60, and 120 min at each temperature. Heat treatment affected serum viscosity. A temperature of 82°C applied for 2 hr resulted in a 17-30% loss of serum viscosity depending on the cultivar. Treatment at 112°C applied for 2 hr caused 67-82% loss, again depending on the cultivar.     

Changes in Oligosaccharide Content, Enzyme Activities and Dry Matter during Controlled Germination of Cowpeas (Vigna Unguiculata)

Cowpeas were germinated at 25, 30, and 35°C for 12, 24, 48, and 72 hr. Stachyose disappeared after 48 hr germination at 30°C while 85 and 95% reductions occurred at 35°C for 48 and 72 hr. respectively. Total oligosaccharide reduction was significantly greater at 30°C than at 25°C. Protease and amylase activities and rootlet development were minimal after 24 hr germination but increased thereafter. Anerobic incubation was ineffective in furthering reduction of olicosaccharides in seeds germinated at 25 or at 30°C for 12 or 24 hr. Total protein and carbohydrate contents were relatively unaffected.     

Comparative study on color,viscosity and related enzymes of tomato juice treated by high-intensity pulsed electric fields or heat

The effects of high intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1,500 μs using bipolar 4-μs pulses at 100 Hz) on color parameters and viscosity, as well as peroxidase (POD), pectin methylesterase (PME) and polygalacturonase (PG), were evaluated during 77 days of storage at 4 °C and compared to thermal treatments at 90 °C for 1 min or 30 s for unprocessed tomato juice. HIPEF-treated tomato juice showed higher values of lightness than the thermally processed and the untreated juice throughout storage time (P < 0.05). Viscosity of HIPEF-treated tomato juice was also greater than both thermally treated and untreated for the first 35 days of storage. POD of HIPEF-treated tomato juice was inactivated by 97% whereas in the case of the thermally treated, 90 and 79% inactivation was achieved after 1 min and 30 s, respectively. The highest PME inactivation in tomato juice was obtained by PEF (82%) and heat treatment at 90 °C for 1 min (96%). PG of PEF-treated tomato juice was inactivated by 12% whereas thermal treatments at 90 °C for 1 min or 30 s achieved 44 and 22%, respectively. Despite the low rates of PG inactivation obtained, the pattern followed in the residual activity along the storage time was similar in the tomato juice treated by HIPEF than the thermally processed.     

Influences of Soaking Temperature and Storage Conditions on Hardening of Soybeans (Glycine max) and Red Kidney Beans (Phaseolus vulgaris)

The influences of soaking treatment and storage conditions on the softening of cooked beans, namely, soybeans and red kidney beans, were investigated. It was revealed that the softening of fresh soybeans and fresh red kidney beans was suppressed during subsequent boiling after soaking treatment at 50 and 60 °C. Furthermore, in treated aged soybeans and red kidney beans that were subjected to storage at 30 °C/75% relative humidity for 6 mo and soaking treatment at 50 to 60 °C, the hardness during cooking was further amplified. This suggested that the mechanism of softening suppression differs depending on the influences of soaking and storage. Analysis of the pectin fraction in alcohol insoluble solid showed insolubilization of metal ions upon storage at high temperature and high humidity in both soybeans and red kidney beans, which suggests interaction between Ca ions and hemicellulose or cellulose as cell wall polysaccharides. The results of differential scanning calorimetry (DSC) showed that aged soybeans exhibited a shift in the thermal transition temperature of glycinin‐based protein to a higher temperature compared with fresh soybeans. From the results of DSC and scanning electron microscopy for aged red kidney beans, damaged starch is not conspicuous in the raw state after storage but is abundant upon soaking treatment. As for the influence of soaking at 60 °C, it can be suggested that its influence on cell wall crosslinking was large in soybeans and red kidney beans in both a fresh state and an aged state.     

A Simple Technique to Improve the Firmness of Cooked Potato Tissue

Potato tissue samples with varying cell turgor pressures were prepared by soaking in mannitol solutions (0 to 0·5 M ). Increased concentration of mannitol in the soaking solutions decreased the cell turgor pressure in potato tissues providing samples with varying degrees of turgidity or plasmolysis. Firmness changes in potato tissues of differing turgor pressure during cooking were examined using a Zwick universal testing machine and also by chewing tests. A modified device attached to a Zwick machine facilitated complete immersion of a potato disc in circulating boiling water, providing rapid and reproducible heat transfer in the tissue during firmness measurements. Tissue firmness expressed as the force required to cause 10% strain in the sample varied in potato discs treated with differing mannitol solutions. Potato discs soaked in 0 to 0·3 M mannitol solutions were more turgid at 20°C than other samples and showed higher tissue firmness. However, when discs of potato were heated in the range of 20–90°C, samples treated with 0·4 and 0·5 M mannitol solutions showed some increase in tissue firmness while all other samples exhibited a rapid decline. Bite-force measurements on potato discs also indicated a rapid loss of tissue firmness in turgid samples. Potato tissues when cooked after soaking in 0·4 or 0·5 M mannitol solution showed more intact and inflated cells than other samples. © 1997 SCI     

FIRMNESS AND THERMAL CONDUCTIVITY OF RED BEETS IN STORAGE

Firmness and thermal conductivity of “Detroit Dark Red, Ferry's Strain” and “Ruby Queen” beets were determined after storage at: 0°C, 95% relative humidity (RH); 12.8°C, 24% RH, and 1.7°C, uncontrolled humidity. Firmness at fixed temperature and humidity conditions decreased with storage; it could be described by a first order rate equation. At a fixed temperature (1.7°C) and uncontrolled humidity, magnitudes of firmness varied as the humidity varied; in contrast, thermal conductivity was influenced very little. At 0°C and 95% rel. humidity, thermal conductivity remained essentially constant for four weeks. The magnitude of thermal conductivity, at room temperature and on the day of harvest, was about the same for four different varieties of beets; “King Red,”“Detroit Dark Red, Ferry's Strain,”“Ruby Queen,” and “Detroit Dark Red, Morse's Strain;” it ranged between 0.579 and 0.600 W/m °K.     

Studies on aeration with refrigerated air—III. Chilling of wheat with a modified chilling unit

Two trials on the cooling of grain with refrigerated air are described. The chilling unit had the fan positioned after the evaporator to lower relative humidity of the cooled air entering the grain. A bin containing 699 metric tonnes of wheat was cooled in summer from 30–37°C to 18–19°C in 160 hr at an energy consumption of 4·6 kW/hr/tonne. The second bin containing 863 tonnes of wheat was cooled in winter from temperatures of up to 42°C to 15–21·5°C in 236 hr at an energy consumption of 4·7 kW/hr/tonne. It was shown that grain was not moistened as a result of cooling. The importance of controlling both air temperature and humidity in the cooling system are discussed and this method is compared with aeration using ambient air.     

The effect of popping,soaking, boiling and roasting processes on antinutritional factors in chickpeas and red kidney beans

This study was conducted to determine the effect that a popping head (like a rice cake machine), a low-shear and low-water processing technology, has on the concentration of antinutritional factors in chickpeas and red kidney beans. Seeds were popped under several parameters (popping time, sample format and equipment type) and analysed against soaking (1:5 w/v in reverse osmosis water for 24 h), roasting (100 g at 180 °C for 20 min) and boiling (1:5 w/v in reverse osmosis water at 100 ± 1 °C for 1 h) processes. Popping and roasting significantly reduced phytic acid content in chickpeas (6%–22%) and red kidney beans (16%–39%). In contrast, phytic acid content after soaking and boiling was not significantly different to raw seeds. Condensed tannins were significantly reduced in red kidney beans after soaking (74%), boiling (100%) and 4 s popping (28%–42%) treatments and increased in both pulses after roasting (137%) and 8 s popping (21%–47%). Further analysis showed that the soluble phenolic content increased with popping, but total and bound phenolic content was reduced. These results demonstrate that the high temperatures and pressures applied during the popping process effectively reduce antinutritional factors in pulses, compared to conventional processing methods.     

Influence of Soybean Variety and the Method of Processing in Tofu Manufacturing: Comparison of Methods For Measuring Soluble Solids in Soymilk

The measurement of percent solids in soymilk was compared by three methods: light scattering, refractive index, and hydrometry. Soymilks were prepared from Vinton, Amsoy 71, and Weber variety soybeans by grinding the hydrated soybeans in (A) 20-25°C water, (B) 100°C water, and holding the slurry temperature above 90°C for 10 min or (C) soaking the soybeans in 45°C 15% ethanol solution for 12 hr and grinding in 20-25° water. Hydrometer readings at 80-90°C showed no correlation with soymilk percent solids. Light scattering was found more accurate at measuring percent solids compared with refractive index. Significant differences were found between the standard curves of percent solids vs light scattering due to the variety of soybeans and the processing conditions.     

Effect of starter cultures on properties of soft white cheese made from camel (Camelus dromedarius) milk

This experiment was conducted to investigate the effect of starter cultures on the physicochemical properties, texture, and consumer preferences of soft white cheese (SWC) made from camel (Camelus dromedarius) milk. The experiment was laid out in a completely randomized design with 5 treatments [starter cultures; i.e., 1 thermophilic (STI-12), 2 blended (RST-743 and XPL-2), and 2 mesophilic (R-707 and CHN-22) cultures]. Starter cultures STI-12 and RST-743 were inoculated at 37°C, whereas XPL-2, R-707, and CHN-22 were inoculated at 30°C. Camel milk inoculated using STI-12 and RST-743 cultures resulted in faster acidification than XPL-2, R-707, and CHN-22 cultures. Camel milk SWC made using STI-12 and CHN-22 cultures gave lower pH (4.54) and titratable acidity (0.59), respectively, whereas R-707 culture resulted in high cheese yield (13.44 g/100 g). In addition, high fat (20.91 g/100 g), protein (17.49 g/100 g), total solids (43.44 g/100 g), and ash (2.40 g/100 g) contents were recorded for SWC made from camel milk made using RST-743 culture. Instrumental analysis of cheese texture revealed differences in resistance to deformation in which camel milk SWC made using RST-743 culture gave higher firmness (3.20 N) and brittleness (3.12 N). However, no significant difference was observed among camel milk SWC adhesiveness made using different starter cultures. Consumer preference for appearance, aroma, taste, and overall acceptances of SWC were affected by inoculation of starter cultures. Considering curd firmness, cheese yield, compositional quality, and textures using STI-12, RST-743, and R-707, these cultures were found to be better for the manufacture of camel milk SWC.     

Histamine Production in Soy Extended Tuna Salads

Histamine production in tuna salads extended with textured soy protein (TSP) was evaluated. Salads were inoculated with five known histamine-producing bacteria and held at 8°C, 24°C, and 37°C for up to 48 hr. Addition of 30% TSP to tuna salads resulted in higher initial pH and favorable growth conditions for microorganisms and histidine decarboxylase activity. Addition of 15% TSP provided an initial pH for maximal enzyme and histamine production but somewhat slower microbial growth. Tuna salad extended with either 15% or 30% TSP developed toxic levels of histamine (>50 mg/l00 g) when held at either 24° or 37°C for 6 hr. Nonextended tuna salads did not develop toxic levels of histamine even when inoculated with known histamine-producing bacteria and held at 24° or 37°C for 48 hr.     

Parboiling of paddy by simple soaking in hot water

Parboiling of paddy by mere hot water soaking, without steaming, has the advantage of not requiring a boiler. Soaking at a temperature 10–15°C above the gelatinization temperature (i.e. generally at about 80–85°C) is necessary to achieve fair to moderate gelatinization (i.e. parboiling). However, soaking at such temperatures for a time sufficient for the water to penetrate and gelatinize the grain core invariably leads to over-imbibition of moisture, husk splitting and leaching; soaking for less time, on the other hand, leaves many grains with 'white belly'. The best method therefore is to soak the grain for such time as to imbibe about 30% moisture (wet basis) (i.e. for about 1 1/2–2 hr), drain out the water, and temper the hot paddy for another 1–2 hr. This process yields optimally parboiled paddy without 'white belly' or grain splitting and with reasonably good milling quality and colour.     

Effect of Thermal Processing on the Survival of Foot-and-Mouth Disease Virus in Ground Meat

Foot-and-mouth disease virus was examined for its stability during cooking in tissues from infected cattle. The 0₁ (CANEFA 2) serotype of foot-and-mouth disease virus survived in lymph node tissues after heating for 2 hr at 69°C, for 1 hr but not for 2 hr at 82°C, and for 15 min but not for 0.5 hr at 90°C. Incorporation of 1% NaCl into suspensions of infected lymph nodes enhanced viral survival after heating for 0.5 hr but not for 1 hr at 90°C. The virus did not survive in either ground beef or meatballs contaminated with infected lymph node tissue, when processed to internal temperatures of 93.3, 96.1 or 98.8°C using commercial thermal processing procedures. Accurate temperature measurements were achieved with a temperature sensitive indicator disc developed in this study.