A MARANTHUS CRUENTUS LECTIN: PURIFICATION, STABILITY, AND SOME BIOCHEMICAL PROPERTIES

Amaranth lectin from Amaranthus cruentus seeds was isolated, purified and partially characterized. The purification method used was based on its ability to interact with fetuin. Effects of temperature, pH and buffers and concentration were determined by measurement of lectin hemagglutination activity. Amaranth lectin biological activity was best maintained at temperatures between 4 and 30°C and pH's above or below 5. It was possible to store amaranth lectin at 4°C in acetate buffers, pH 4.8, for prolonged periods and to concentrate it 10-fold by ultrafiltration with only 18% loss of activity. A subunit molecular weight of 32,500 daltons was determined by SDS-PAGE for amaranth lectin.     

SCALE UP ISOLATION OF IMMUNOGLOBULINS FROM PIG SERUM BY IMMOBILIZED METAL AFFINITY CHROMATOGRAPHY

The immunoglobulins (Ig's) are proteins with a well-known structure and function. In immunocompetent animals (individuals), these proteins counteract the pathogenic microorganisms. However, under pathological conditions or in a precocious weaning, exogenous immunoglobulins, among other treatments, are being used to avoid and cure some diseases. There is much interest in developing alternative methods for the isolation of functional immunoglobulins from sources different than maternal colostrum and milk. Pig serum contains a high concentration of Ig's and it has the advantage of containing not only IgG but also IgA and IgM in a greater proportion than found in any other species. Pig serum is a major contaminant generated by meat producers that could be used as a biotechnological alternative for blood or milk whey. Immunoglobulins G, A and M were isolated from porcine serum using Nickel-Iminodiacetate-Sepharose 6B in a single step at an analytical level. The procedure was easily scaled up to a 30 ml bed column. Serum immunoglobins (176 ml; 8.7 g) were adsorbed to the gel in buffer, pH 6.0, containing 1.0 M NaCl, and the purified immunoglobulins (735 mg) were eluted using the same buffer, but at pH 5.0. This separation was repeated 27 times without loss of gel capacity. The source of immunoglobulins, the longevity of the adsorbent, the gel capacity (29 mg/ml bed volume) and the mild conditions allowed rapid isolation of high concentrations of immunoglobulins. This method can serve as an alternative to those currently available for obtaining the three major immunoglobulins for inclusion in animal feeding.     

Production of low-fat Chanco cheese using homogenized milk and adjunct lactic culture

The objective of this study was to determine the effect of the partial homogenization of milk and the use of an adjunct lactic culture on the processing, quality and yield of low-fat Chanco cheese.
  Treatments were: T1 normal-fat control and T2 low-fat control. The low-fat treatments were: T3 using homogenized milk, T4 with adjunct lactic culture and T5 both variables.
   It was concluded that the homogenization slightly increased the time of rest after cutting of the curd, and the addition of adjunct lactic culture increased the acidity of whey during a second agitation. Nevertheless, the total time and pH at the end of the process were normal and without significant statistical difference ( P  > 0.05) between treatments. When using homogenized milk the losses of fat in whey decreased by 50% with respect to the low-fat control and nearly 80% in relation to the full fat control. Consequently, the yield was increased. The physical and chemical characteristics of the Chanco cheese were not affected by the studied variables. With respect to the sensory evaluation, significant differences in colour and aroma did not appear, but there were statistically significant differences (P <  0.05) in taste, hardness, adhesiveness, cohesiveness and elasticity between the full-fat control and all the low-fat treatments. In the case of general acceptance, the treatment with adjunct lactic culture was similar to the full-fat control. In addition, it showed the least difference (mild) in elasticity and taste in relation to this control .     

Rheological properties of flour and sensory characteristics of bread made from germinated chickpea

Breads were prepared from wheat flour supplemented with 0,10,20 and 30% ungerminated or germinated chickpea flour to determine the influence of germination on the sensory acceptability of the baked products. Rheological characteristics of the flours were evaluated by the Brabender farinograph and viscoamylograph, using a wheat flour control. Farinograph development and stability times decreased, and amylograph peak viscosities increased for all fortified flours. Germinated flours showed greater retrogradation upon cooling. Most sensory characteristics of fortified breads did not differ significantly, but the chickpea loaf fortified with 10% germinated flour did not compare favourably with the control.     

HAPTENIC CARBOHYDRATES AFFECT THE THERMAL DENATURATION OF SOYBEAN LECTIN

The effect of haptenic carbohydrates, N-acetyl-galactosamine and galactose, on soybean agglutinin (SBA) thermal denaturation was measured by differential scanning calorimetry (DSC) and batch heating in an oil bath. Thermodynamic parameters were determined by scanning from 30 to 11OC, at 1C/min. Lectin activity was measured by a hemagglutination test after heating at 80, 85, 90 and 95C for 5, 10, 15 and 20 min. Soybean lectin denaturation was an irreversible process with ΔH^±= 120 kcal/mol that was significantly reduced by carbohydrates, and it was a carbohydrate concentration dependent phenomenon. In addition, haptenic carbohydrates induced an increase of the T_max and T_tr of SBA denaturation when compared with soybean lectin solution alone. The loss of lectin activity was faster in absence of haptenic carbohydrates than those obtained from solutions with the specific sugars. It was concluded that haptenic sugars protected the SBA against denaturation.     

ROLE OF OIL ON PHYSICAL PROPERTIES OF CORN MASA FLOURS AND SENSORY CHARACTERISTICS OF CORN TORTILLAS

This study was conducted to evaluate the effect of oil on physical properties of corn masa and sensory of tortillas. Oil from commercial and lab-made whole dry corn masa (DCM) was extracted with hexane. Both flours were reconstituted with 2, and 4% w/w of commercial corn oil, to have 50 and 100% oil reconstituted flours. These levels of reconstitution were to determine the impact of oil on dough properties and sensory characteristics of corn tortillas. The sensory analysis of both types of flours showed the same patterns. The absence of oil did not affect dough stickiness or tortilla reliability. But, low content of oil did adversely and significantly (p<0.05) affect the typical corn tortilla flavor. Presence of oil significantly improved tortilla firmness and chewiness.     

HEAT SHOCK REDUCES BOTH CHILLING INJURY AND THE OVERPRODUCTION OF REACTIVE OXYGEN SPECIES IN YELLOW PITAYA (HYLOCEREUS MEGALANTHUS) FRUITS

ABSTRACT

Yellow pitaya fruits were heat‐shocked (25C/24 h), stored at 2C for 14 days and then held for 13 days at 18C. Chilling injury (CI), respiration rate, hydrogen peroxide (H₂O₂), superoxide anion radical (O₂•^‐) and lipid peroxidation product (LPP) levels were measured. Pitting and browning were detected in the control fruit when moving from 2 to 18C. Minor CI symptoms were found in the treated fruit. There was a rapid increase in the levels of H₂O₂, O₂•^‐ and LPP in the control fruits when moved to 18C. At the end of the storage, the levels of these compounds were 4.5‐, 4.9‐ and 6.2‐fold higher, respectively, in the control than in the treated fruit. The results suggest that the reactive oxygen species levels in the heat‐shocked fruit were adequate for normal ripening, while the levels in the control group were excessively high, inducing CI symptoms.

PRACTICAL APPLICATIONS

Refrigeration is a technique that can be used to extend shelf life of yellow pitaya fruit. Nevertheless, these fruits are susceptible to chilling injury. This research was developed to study the effect of heat shock treatment on the preservation of whole yellow pitaya fruit during refrigeration. Preheating fruit at 25C for 24 h before storage at 2C for 14 days prevented chilling injury during shelf life at 18C. Thus, the combination of heat shock and refrigeration delays the senescence of yellow pitaya fruit and therefore improves its shelf life. Furthermore, this treatment could be useful during quarantine treatments of fruit fly‐infested fruit.

     

Physical, Chemical, Nutritional and Sensory Properties of Corn-Based Fortified Food Products

Product formulations and processing methods were developed using seven corn-based flours. They were fortified with various levels of sesame, chickpea, soybeans, powdered egg, nonfat dry milk, lysine, and methionine. Products were formulated to provide as closely as possible the FAO requirements for essential amino acids and to have acceptable physical, chemical, nutritional, sensory properties and cost. The overall nutritional value was increased at least by 92% as compared to similar existing products. There were no obvious differences in physical properties of the fortified flours and products as compared to commercial counterparts. The protein cost of the fortified products was less than that of food from animal sources; the PER values being the same or higher.