Biogenic Amines in Meat and Meat Products

It has been recognized for some time that biogenic amines occur in a wide range of foods, among them meat and meat products. Meat is an important component of the diet in developed countries. The presence of these amines in food is of interest for two reasons: firstly, for toxicological reasons, in the sense that high levels of dietary biogenic amines can be toxic for certain consumers, and secondly, for their role as possible quality indicators. Based on these two premises, the present article offers a new analysis on aspects of toxicology and on the use of biogenic amines as a quality control method, as well as on their presence in meat and meat products. The article focuses particularly on factors affecting the production of biogenic amines, with reference to various parameters relating to microorganisms, meat raw materials, and processing conditions. A better understanding of the factors determining their formation (i.e., microorganisms, raw materials used, and technological processes applied) and their effects could lead to ways of controlling their production, limiting their presence in the end product, and hence, rendering them less toxic.     

EFFECT OF HARVESTING SEASON AND POSTHARVEST TREATMENTS ON STORAGE LIFE OF MEXICAN LIMES (Citrus aurantifolia Swingle)

Changes in susceptibility to chilling of citrus fruits vary with the low temperature applied, storage period, growing area, season, time of harvest and postharvest treatments. The objective of this study was to determine the effect of low temperatures on the quality of Mexican limes coated with wax applied through spraying or dipping, and treated with thiabendazole (TBZ) at 500 ppm and gibberellic acid (GA3) at 250 ppm. Weight loss, % of juice, degrees Brix, titratable acidity, color development and severity of chilling injury were examined weekly during storage. The results, obtained from fruit collected in two harvest periods, demonstrated that limes during the maximum production period of harvest in July, in contrast to those harvested in September, retained 90.6% of their fruit marketability. The conditions under which the best quality was obtained were the following: waxing by dipping + TBZ at 500 ppm + GA₃ at 250 ppm and 10C storage temperature with RH at 85–90%.     

Brief note: Differences in intracellular localization of corn stunt spiroplasmas in magnesium treated maize.

Maize plants infected with Spiroplasma kunkelii show symptoms similar to that of plants in a magnesium-deficient soil, and it has been shown that the spiroplasma alters the plants’ magnesium absorption. In the current study we compared changes associated to either spiroplasma infection, two soil magnesium levels and their combinations. Plant symptoms were recorded and correlated with transmission electron microscopy observations. Plants grown on a high magnesium treatment showed no macroscopical alterations nor organelle ultrastructural alterations, while plants on a low magnesium treatment showed macroscopical vein yellowing and, ultrastructurally, they had most chloroplasts and mitochondrial membranes altered. Infected plants on a low magnesium treatment had an ageing aspect, ultrastructurally showed chloroplasts and mitochondrial alterations similar to those non-infected and grown on a low magnesium treatment, and spiroplasma cells were found in phloem cells, but outside their cytoplasm. Infected plants on a high magnesium treatment showed similar symptoms and ultrastructural alterations as either non-infected plants on the low magnesium treatment or in infected plants on the low magnesium treatment, but differ from them in that the spiroplasma cells were located inside the cytoplasm. Results suggest that magnesium is involved in the plant-pathogen interaction.     

KINETICS OF ACRYLAMIDE FORMATION DURING TRADITIONAL AND VACUUM FRYING OF POTATO CHIPS

Acrylamide is considered a carcinogen in animals and a possible carcinogen in humans. It has been found in starch‐rich foods cooked at high temperatures. Vacuum frying (10 Torr) was investigated as a possible alternative to reduce acrylamide formation in potato chips. The cultivar Atlantic was used to determine the kinetics of acrylamide formation during traditional and vacuum frying at different temperatures. There was a 94% decrease in acrylamide content when potatoes were fried to the same final moisture content (1.5% ± 0.3% w.b.) under vacuum compared to those fried under atmospheric conditions. Acrylamide accumulation under vacuum frying was modeled using first‐order kinetics (during traditional frying, the logistic kinetic model was used). The behavior of the kinetics of acrylamide content in potato chips fried under the two processes was different mainly because of the different temperatures used. During traditional frying, higher temperatures are used (150 to 180C) and acrylamide after some time is produced but starts degrading, producing a constant level of acrylamide content at longer times. During vacuum frying (10 Torr), acrylamide increased exponentially (but at lower levels) for all frying times.     

A linear dynamic system approach for cattle herd optimal shaping

The time evolution of a herd of cattle is modelled as a linear dynamic system with slow time variation in model parameters. From this model, the optimal policy for the herd shaping is established, allowing the minimal initial cost with cattle acquisition and the maximal farm resources utilization in the steady state. The same methodology can be employed in several different production schemes, with different constraints and different objective functions. The optimization problem is formulated as a convex programming one, being solved with efficient algorithms, while keeping guaranteed convergence to the global optimum. This methodology is simpler than the dynamic programming optimization method.     

MACRODONTIN, A NEW PROTEASE ISOLATED FROM FRUITS OF PSEUDANANAS MACRODONTES (MORR.) HARMS (BROMELIACEAE)

A cysteine proteinase was isolated from immature fruits of Pseudananas macrodontes (Morr.) Harms, a species taxonomically close to pineapple grown in the northeast of Argentina. The protease is active at pH 7.0 to 10.5, and rather unstable at temperatures over 45C. Crude extracts were purified by acetone fractionation followed by chromatofocusing at the pH range 4.5 to 6.5. Two main proteolytic fractions were obtained: fraction I (M_r= 20.6 kDa, pI = 5.9) and fraction II (M_r= 19.3 kDa, pI = 5.3), both homogeneous by gel-filtration and SDS-PAGE criteria. This new plant protease (“macrodontin”) could be valuable in processes carried out in neutral-weak alkaline media. The thermal behavior of the crude enzyme is also a useful property, since it could be easily inactivated in foodstuffs by heating 10 min at 75C. Comparison of macrodontin and alcalase proteolytic behavior on soy concentrates is presented.     

RELATION BETWEEN THE FREE AMINO ACIDS, ANSERINE AND THE TOTAL VOLATILE BASIC NITROGEN PRODUCED IN MUSCLE OF HAKE (MERLUCCIUS MERLUCCIUS, L.) DURING ICED STORAGE

This work studied the development of free amino acids (FAAs) and dipeptide anserine as quality indices for gutted hake stored in ice for 25 days. The correlation of these compounds was determined with total volatile basic nitrogen (TVBN) which has been used as a quality index, for fish stored in ice. The most abundant free amino acids in hake muscle were found to be threonine, glycine, alanine, glutamic acid, β-alanine methylhistidine. lysine and the dipeptide, anserine. The only hydrophobic free ammo adds which exhibit significant differences (P<0.05) throughout storage was tryptophan. moreover, this amino acid exhibited a very high correlation (r=0.951) with TVBN. A significant decrease in anserine (P<0.05) correlated with the increases in 1-methylhistidine and β-alanine throughout storage. These changes also exhibited a very high correlation with TVBN. Therefore, 1-methylhistidine, β-alanine anserine and tryptophan could be used as quality parameters for hake stored in ice.