Abstract Jumbo squid (Dosidicus gigas) muscle hardness has been related to hydroxylysyl-pyridinoline (HP) formation (collagen fibre stabilization) via condensation of oxidized ε-amino groups of lysine and/or hydroxylysine by lysyl oxidase (LOX). Previously published literature has suggested the presence of LOX isoforms in squid muscle. Thus, the objective of the present research was to test the hypothesis that squid LOX isoforms exist in fresh mantle muscle. A semi-pure LOX extract (SPLE) was used to perform an immunoblotting assay using two commercial human-LOX antibodies. Furthermore, SPLE (specific activity of 20 mU/mg of protein) was tested in vitro for possible HP formation using several collagenous materials. Immunoblotting assay confirmed the presence of squid LOX at 32 kDa and its isoforms at 34 kDa and 24 kDa. Although LOX oxidized ε-amino groups on collagenous materials, no HP formation was detected. However, the latter could promote interesting collagen functional modifications.

ABSTRACT Nowadays agriculture is facing constantly challenges to produce more and better food for a growing population under a changing climate scenery. To afford this demand, agricultural practices must innovate in new methods for crop production, nutrition management, and plant health. In addition, the development of new compounds or biological agents able to improve plant yield (regulating plant physiology, metabolism, crop performance), and agro-product quality, are also necessary. In the last decade, agents with these characteristics have been proposed for a sustainable agriculture. These agents, defined as biostimulants, have showed to improve plant nutrition, quality, yield and abiotic tolerance in different agricultural crops. In particular, the use of protein hydrolysates as biostimulants offers promising results to reduce the use of agrochemicals and improve productivity parameters in a variety of cultivars, in agree with the modern agricultural production challenges. The present review is focused in the use of protein hydrolysates as plant biostimulants, describing typical and potential agro industrial by-products as sources substrates for protein-based biostimulants formulation, and commercial or experimental proteolytic enzymes used for hydrolysate production. Moreover, critical aspects during protein biostimulants manufacture, functional profiling and its applications are discussed. Finally, recent advances for the evaluation of protein hydrolysates on plant physiology and metabolism under experimental and commercial scale are also documented. Concluding in the necessity to conduct structural studies, in order to identify and produce bioactive peptides with agricultural applications.

Abstract The most common process that Mexican artisanal cheese industry applies to whey to add value, is the production of requesón (whey cheese). However, the technological profile of the whey depends on its physicochemical characteristics. The objective of the present study was to characterize the primary (LPQC) and secondary (LSQC) whey from the production of artisanal “coccid cheese” (asadero), and the properties of requesón cheese made from these types of whey. The LPQC had 6.6% of solids content similar (p≥0.05) to sweet whey from fresh cheese manufacture (LQF, control), although a lower pH (5.3 vs 6.5) and protein content (0.4 vs 0.7 %). On the contrary, the LSQC had a high content of solids, protein and fat (9.4, 1 and 4.2 %, respectively), characteristic that was reflected in a higher content of solids and fat in requesón made from this whey, in comparison with the composition of requesón made with LPQC and LFC. Firmness (N), adhesiveness (- N) and cohesiveness parameters of requesón samples were in a range of 0.050-0.18 (N), 0.07-0.26 (-N) and 0.40-0.84, respectively, obtaining lower values of hardness and adhesiveness in requesón from LPQC, and a greater cohesiveness in requesón from LSQC (p<0.05). In conclusion, the physicochemical characteristics of whey from cheesemaking determined the chemical composition as well color and textural properties of requesón (whey cheese).

Resumen El proceso que más utiliza la industria quesera artesanal mexicana para agregar valor al lactosuero es la producción de requesón. Sin embargo, el perfil tecnológico del lactosuero depende de las características fisicoquímicas que posee. El objetivo del presente estudio fue caracterizar el lactosuero primario (LPQC) y secundario (LSQC) proveniente de la producción de queso cocido (asadero) de Sonora, y del requesón elaborado a partir de estos. El LPQC tuvo un contenido de sólidos alrededor de 6.6 % similar (p≥0.05) al lactosuero dulce de queso fresco (LQF, control), aunque con un menor pH (5.3 vs 6.5) y contenido de proteína (0.4 vs 0.7 %). Por el contrario, el LSQC tuvo un alto contenido de sólidos, proteína y grasa (9.4, 1 y 4.2 %, respectivamente). La composición química del requesón elaborado con LSQC presentó un mayor contenido de sólidos y grasa, respecto al requesón elaborado con LPQC y con LQF (control). Los parámetros de firmeza, adhesividad y cohesividad de todos los requesones estuvieron en un rango de 0.05-0.18 (N), 0.07-0.26 (-N) y 0.40-0.84 respectivamente, obteniéndose menores valores de firmeza y adhesividad en requesón de LPQC, y una mayor cohesividad en requesón de LSQC (p<0.05). Las características fisicoquímicas del lactosuero de queso cocido determinaron la composición química y características de color y textura en el requesón elaborado.