Role of Pectin Methylesterase in Firmness of Canned Tomatoes

Abstract

SUMMARY Four sets of eight tomatoes were subjected to four blanching times of 30, 60, 90, and 120 set at 100°C. Two fruits in each set were also subjected to holding times of 5, 10, 15, and 20 min between the blanching and exhausting operations. Pectic substances were determined as water‐soluble, ammonium‐oxalate‐soluble, and dilute‐hydrochloric‐acid‐soluble fractions. The methoxyl content of each fraction was also determined. Firmness was determined by objective measurements. The 30‐see blanching treatment yielded the firmest tomatoes. These fruits were also characterized by the highest content of ammonium‐oxalate‐soluble pectin. The activity of pectin methylesterase was highest in treatments consisting of 30 see of blanching and a lo‐min holding time. The activity of pectin methylesterase seemed to be greatly suppressed after 90 set of blanching.

Effect of temperature and pressure on the activity of purified tomato polygalacturonase in the presence of pectins with different patterns of methyl esterification

“…However, the food industry can benefit from a controlled activation of PME, while PG is selectively inactivated by choosing proper combinations of pressure and temperature. Consequently, the texture and juice viscosity of tomato-based products will be improved, as the partly deesterified pectin chains, formed after reaction with PME, may crosslink in the presence of divalent cations and are less susceptible to h-elimination chain breaking reactions during thermal processing (Alonso, Canet, & Rodriguez, 1997;Hoogzand & Doesburg, 1961;Hsu, Deshpande, & Desrosier, 1965;Stanley, Bourne, Stone, & Wismer, 1995;Steinbuch, 1976;Stolle-Smits, Beekhuizen, Recourt, Voragen, & van Dijk, 2000;Van Buren, 1979;Van Buren & Pitifer, 1992). Former enzyme inactivation studies, i.e.…”

Low‐temperature Blanch Improves Textural Quality of French‐fries

“…The PME produces free carboxylic groups which can react with divalent ions, e.g. calcium and magnesium, creating more rigid structures and increasing the firmness (Hoogzand and Doesburg, 1961;Hsu et al, 1965;Bartolome and Hoff, 1972;Lee et al, 1979;Van Buren, 1979;Chang et al, 1993;Andersson et al, 1994). For this reason, it is a common practice to add calcium salts to vegetable products as a firming agent (Buescher et al, 1981), especially heat processed foodstuffs (Wiseman, 1985;Baduí, 1993).…”

Hydrogen and Calcium Ion Concentrations Affect Volume of CO2 Puffed Diced Green Bell Peppers

“…Similar results were also shown by Kertesz (1951), Matz (1962, and Sterling (1963). Calcium ions had similar effect in firming cucumber slices (Fleming et al, 1978) and tomatoes (Hsu et al, 1965).…”