ALBERT

Notes: Mixed soy/cow's milk curds were prepared by simultaneous curdling of soy/cow's milk blends, utilizing rennet as cow's milk coagulant and calcium or magnesium sulfate as soymilk coagulant. The method produced curds of similar characteristics (compactness and yield), whether soymilk prepared from soybeans or full-fat soy flour was used. The effect of a number of process variables on curd characteristics was studied, utilizing a fractional factorial design. Generally, large changes in process variables (23 – 230%) produced relatively small charges in curd characteristics (1 – 16%). Protein contents of raw materials and proximate chemical analyses of pure and mixed milk curds, prepared under conditions yielding maximum curd compactness were determined. Protein recoveries in curd preparation were calculated.

Notes: Total plate, halophilic and staphylococcal counts were determined in quick-salted fish cakes after 0, 1, 2 and 3 months' storage without packaging at an ambient temperature of 35–40°C. A rancidity (thiobarbituric acid or TBA) index was also determined in sun-dried and tunnel-dried cakes, before and after desalting, stored under the same conditions for the same lengths of time. Species studied were skipjack, mullet, Spanish mackerel and shark from the Gulf of California. It was found that total plate and halophilic counts behaved similarly, initially increasing with time, passing through a maximum, and then decreasing. Counts increased with decreasing salt and increasing moisture contents of the cakes. Maximum counts obtained were of the order of 106 per gram for cakes made from shark, while negative counts were obtained with cakes made from skipjack after 3 months. No growth of staphylococci was obtained at any time in any of the plated dilutions (10−1 to 10−6). Rancidity of the cakes increased with time, depending upon the following factors: oil content of the species; degree of unsaturation of the oil; drying time of the cakes; presence or absence of hematin pigments; presence or absence of sunlight when drying. Some of the rancid components in the cakes were removed by desalting in boiling water. In a limited taste panel evaluation of the cakes, order of preference was found to correlate well with decreasing rancidity

Notes: The following variables were determined at equilibrium between fish muscle and brine, all as functions of the salt concentration in the brine: salt concentration in the muscle, based on the volume of the muscle; salt concentration in the tissue water of the muscle; distribution coefficient of salt between muscle volume and brine; distribution coefficient of salt between muscle tissue water and brine. Secondary variables which further described the salting equilibria were also found as functions of salt concentration in the brine as follows, all based on unit weight of non-salt solids in the salted muscle: weight of salt (S/NSS), weight of water (W/NSS), and volume (V/NSS).The salt concentration based on the muscle volume was found to increase continually with increasing brine concentration, as did the salt concentration in the tissue water and the salt content expressed as S/NSS. The distribution coefficient based on the muscle volume and the water and volume contents (W/NSS) and (V/NSS) were found to increase at first, pass through a maximum, and then decrease, all with increasing brine concentration. Within the limits of experimental error, the salt concentration in the tissue water was found to equal the salt concentration in the brine, so that the distribution coefficient calculated on this basis was always equal to unity and was independent of the salt concentration in the brine.The volume per unit weight of non-salt solids (V/NSS) was found to be a direct linear function of the water content per weight of non-salt solids (W/NSS) at all temperatures studied. Little difference was found between the equilibrium salting variables when salting was carried out at 5 and at 25°C; on the other hand, possibly due to “cooking” or heat denaturation of the muscle with consequent loss of water at that temperature, all variables were considerably lower when salting was carried out at 37°C. The “mean molar activity coefficient” of sodium chloride in fish muscle was determined as a function of salt concentration in the muscle. It was found to be always greater, and to vary more sharply with salt concentration, than the corresponding activity coefficient of salt in aqueous solution.

Notes: A nitrogen balance study, comparing a low-cost soy-oats infant formula with and without supplemental methionine, was carried out with infants of ages 3 - 26 months at a single equivalent level of nitrogen intake (approximately 850 mg/kg/day). Nitrogen retention was found to be unaffected by methionine supplementation. Com- parison of data obtained in this study with previous research re- vealed that a critical value for intake of total L-sulfur amino acids apparently exists in infants 3 - 26 months of age, below which methionine supplementation will increase nitrogen retention, but above which it will not. This value appears to coincide with that of 49 mg/kg/day recommended for infants by the FNB.

Notes: Trypsin inhibitor and lectins in raw corn-soybean blends (92/8 and 84/16 w/w, dry basis) cooked in limewater decreased with cooking time and increasing lime concentration, with total inactivation occurring, in all cases, after 30 min. These factors, determined in raw corn-soybean (92/8 and 84/16 w/w, dry basis) tortillas decreased with increasing hot plate contact time; total inactivation of both occurred only with 92/8 tortillas after 60 sec. Antinutritional factor inactivation rates were considerably higher for hot plate cooking than for limewater boiling. Soaking cooked blends in liquor after turning off the heat and allowing to cool, followed by grinding into a dough had little effect on antinutritional factors, while washing cooked blends with water resulted in some reduction of both factors. Corn-soybean tortillas prepared with normal heat treatment had no residual factors, while those prepared with minimum heat treatment had insignificantly low residual trypsin inhibitor and no lectins.〈section xml:id="abs1-2"〉〈title type="main"〉SUMMARY & CONCLUSIONSEFFECTS of processing parameters on trypsin inhibitor and lectin contents of corn-soybean tortillas prepared by lime cooking of whole raw corn-soybean mixtures may be summarized as follows.〈list xml:id="l1" style="custom"〉1Cooking time in boiling limewater and on the hot plate produces the largest reduction of both trypsin inhibitor and lectins. Due to higher temperature and higher initial blend moisture content involved, hot plate cooking exhibits higher inactivation rate than limewater boiling. Total reduction of antinutritional factors is higher when boiling in limewater, however, due to considerably longer processing time employed as compared with hot plate cooking.2Trypsin inhibitor and lectin inactivation rates on boiling in limewater appear to increase with increasing lime concentration due, probably, to additional protein denaturation by higher pH's.3Soaking in cooking liquor after boiling in limewater and turning off the heat results in relatively little reduction of trypsin inhibitor and lectins, because temperature begins to drop after the heat has been turned off.4Some trypsin inhibitor and lectins appear to be leached out into the liquor during cooking and removed by subsequent washing. This effect, however, produces relatively little reduction of both antinutritional factors.5Grinding of cooked corn-soybean mixtures into a dough involves relatively low temperatures and produces very low temperature rise; consequently, this process probably results in negligible change in trypsin inhibitor and lectins.6In all experiments performed, lectin agglutinating activity to human blood was appreciably lower and more easily destroyed by heat treatment or increasing lime concentration, than to rabbit blood.7Tortillas prepared by limewater cooking of whole raw corn-soybean mixtures by the traditional method would probably be free from trypsin inhibitor and lectins if normal heat treatment, resulting from employment of usual processing conditions (i.e., boiling in limewater for 30 min and cooking 45 sec on a hot plate, alternating sides, 15 sec each side) were applied. In this case most antinutritional factor activity would be destroyed by limewater cooking, with additional heat treatment applied on the hot plate serving as a safety factor. If, on the other hand, a heat treatment lower than normal were applied, tortillas with residual trypsin inhibitor, but no lectins, could result. Trypsin inhibitor level, however, would probably be too low to be of any significance.It can be concluded that, because of the reduction of the concentration of trypsin inhibitor and lectins, corn-soybean tortillas prepared by the method described in this paper would probably be suitable for human consumption.

Notes: A low cost powdered infant formula made from soybeans, oats and sucrose, fortified with methionine, vitamins and minerals, has been developed. A dry process for making the formula, which employs a low-cost Brady extruder, has also been developed. The resulting product is of good microbiological quality and disperses readily in water to give a milk-like suspension of satisfactory stability to settling. The essential amino acid pattern of the formula, its PER and NPU values, nitrogen balance data with infants, proximal chemical analysis, calorie distribution and low level of trypsin inhibitor indicate it to be adequate for feeding infants 3 months or older. Clinical trials with infants also showed that the formula was well accepted and tolerated, and produced adequate weight gain. Retail prices of the product, packed in cans and polyethylene bags, are appreciably lower than those of comparable cow's milk and other soya-based infant formulas available in the market. The product is currently being manufactured and sold in several parts of Mexico.

Notes: With the purpose of evaluating quick-salted fish cakes as a food, proximate chemical analyses, protein quality (Protein Efficiency Ratio and Net Protein Utilization) and bacterial counts of cakes, freshly made and stored for 18 months at an ambient tropical temperature, were de termmed. The cakes were found to contain an average of 30% protein, 60% salt and 10% moisture. Freshly made cakes were found to be superior, and 18-month-old cakes slightly inferior to casein, in both PER and NPU values Finally, total plate and halophilic counts of freshly made cakes, already low (9,000 and 12,000/g, respectively), were found to decrease to ahnost zero after 18 months. Considering present U.S. Recommended Daily Allowances for high quality protein foods, it was calculated that each 450-g cake, costing $0.44, would be sufficient to cover the daily protein needs of three adults or possibly two adults and two young children. The average daily protein cost for each adult would be $0.15.

Notes: A simple and inexpensive method for enriching tortillas with soy proteins was studied. The method consisted of application of the traditional process for making corn tortillas to whole raw corn-soybean mixtures: lime cooking of a mixture, allowing the cooked mixture to stand overnight in the cooking liquor, washing the mixture with tap water, grinding the cooked mixture into a dough, and making tortillas from the dough. This method of enrichment was found to give tortillas with significantly higher protein content and protein quality than normal un-enriched tortillas. PER and NPU values of tortillas containing 8% and 16% soya were found to be comparable to those obtained with tortillas enriched with soy flour or with amino acids lysine and tryptophane. The presence of soybeans in tortillas so enriched was found to be not significantly detectable by a trained panel, at least up to a soya level of 16%. Toxic factors present in raw soybeans were not detected in enriched tortillas by the urease method, having been apparently inactivated by the tortilla-making process. Enrichment by this method is cheaper than enrichment with soy flour or with amino acids. The method permits uniform introduction of soya proteins within the tortillas, and changes neither food recipes nor eating habits.

Notes: Radio-frequency heating at 60 and 2450 MHz in conveyorized equipment was compared with conventional hot water treatment for pasteurization of small cured hams packed in Cryovac casings inside moulds. For lean 2-lb hams, treatment time to reach the desired central temperature could be reduced to 1/3 by heating in a condenser field tunnel operating at 60 MHz, with substantial reduction of juice losses and a tendency to improve sensory quality compared with that obtained with hot water processing. Treatment time could be further reduced by roughly the same extent by processing at 2450 MHz, but product thickness had to be reduced to secure sufficient heat penetration. Temperature gradients end juice losses were comparable to those in hot water treatment. At 2450 MHz in particular, but also at 60 MHz, bacterial surface counts were considerably higher than in the controls, suggesting the need for higher final surface temperature or supplementary heat treatment, which will lower the differences in processing time and juice loss between methods.

Notes: The diffusion coefficient for the penetration of salt into swordfish muscle was not constant but depended upon the salt concentration in the muscle and upon the temperature; the coefficient-salt concentration curve for 25°C had a minimum value at a salt concentration of approximately 1.5 moles/liter and was always lower in fish muscle than in aqueous salt solutions of the same salt concentration as the muscle. Other parameters which also served to characterize the migration of salt in fish muscle were determined as follows: the equivalent conductance of salted fish muscle was found to be an inverse linear function of the square root of the salt concentration in the muscle and to be always lower in muscle than in aqueous solutions of the same concentration as the muscle; the sodium and chloride ion transference numbers, found to be approximately of the same magnitude in muscle and in water, exhibited the same qualitative variation with salt concentration and with temperature in both media.As in aqueous solution, the diffusion coefficient and the equivalent conductance of salt in fish muscle were found to increase with increasing temperature. It was found that experimental values of the diffusion coefficient at a given temperature agreed reasonably well with values predicted by the equation 〈inlineGraphic alt="inline image" href="urn:x-wiley:00221147:JFDS218:JFDS_218_mu1" location="equation/JFDS_218_mu1.gif"/〉 is the diffusion coefficient in the muscle at infinite dilution and γ is the “mean molar activity coefficient” of salt, also in the muscle, at concentration c. The activation energies for salt diffusion in fish muscle and in water at infinite dilution were both found to be of the order of 4700 calories per gram-mole, a value within the region of hydrogen-bonding energies.