Safety of tomatillos and products containing tomatillos canned by the water-bath canning method

Three studies were conducted to evaluate the safety of tomatillos and products containing tomatillos canned by the water-bath processing method. In the first study, plain tomatillos were processed for 25, 37.5, 50 and 62.5 min. In the second study, five tomatillo/onion combinations were prepared while five tomatillo/green chile combinations were prepared in the third study. pH evaluations were conducted to determine safety in all studies using pH 4.2 as the cut-off value. No differences in the pH of plain tomatillos were detected due to processing time. All jars of plain tomatillos had pH values below 4.1. All combinations of tomatillos/onions and tomatillos/green chile containing more than 50% tomatillo had pH values below the 4.2 cut-off value. Results of the three studies indicate (1) acidification of plain tomatillos is probably unnecessary for canning by the water-bath processing method and (2) combinations of acidic tomatillos and low-acid onions or green chile must contain more than 50% tomatillos to have a pH low enough for safe water-bath processing.     

Effect of nitrogen,phosphorus and potassium on yields and nutrient levels in onions grown on a sphagnum peat soil

Abstract

Onions were grown on two areas of sphagnum peat. One (old area) had been fertilized and cropped for a 5‐year period and the other (new area) had not. Fertilizer treatments on both areas consisted of an N, a P and a K series. Each nutrient was applied at four rates in combination with constant rates of the other two.

In practically all instances comparable treatments resulted in lower N, P and K levels in plant tissue samples from the new area than from the old where residual effects from previous cropping and fertilization were evident. Yield data indicate that initially, previously unfertilized sphagnum peat should receive N, P and K at 275–300, 40–50 and 70–80 kg/ha respectively.     

Storage characteristics and relationships between microbial growth parameters and shelf life of MAP sliced onions

Microbial proliferation and sensory quality aspects of sliced onions were tested at different temperatures (−2, 4 and 10 °C) and atmospheric conditions (with or without 40% CO₂ + 59% N₂ + 1% O₂). The relationships among microorganism growth parameters (the initial cell number (N₀), the maximum cell number (N_max), the maximum specific growth rate (μ_max) and lag-phase (λ)) and the microbial or sensory shelf life were determined. The microorganism growth parameters were obtained by fitting the modified Gompertz equation to the microbial counts. The results showed that color intensity (yellowness), sensory scores and microbial counts increased, and firmness decreased during storage. The total plate counts (TPC) provided the best indication of the spoilage organism growth capacity under tested temperatures and atmospheric conditions. The microbial shelf lives of the tested onions in 40% CO₂ + 59% N₂ + 1% O₂, or at −2, 4 and 10 °C, were 12.5, 9.5, 7, 12, 9 and 6 days, respectively, and their sensory shelf lives were 12, 8, 5, 10.5, 7 and 5 days, respectively. The lag time (λ) of the TPC, coliforms, pseudomonads and yeasts correlated well with the microbial and sensory shelf life results. The correlations between microbial and sensory shelf life, and the μ_max of TPC, lactic acid bacteria (LAB) and coliforms were between (−0.61 and −0.85). The initial microbial counts (N₀) of the five microorganisms showed a slight correlation, and the maximum microbial counts (N_max) of this group showed no obvious correlation with onion shelf life, apart from the LAB and yeasts.     

Heterosis of purple blotch (<Emphasis Type="Italic">Alternaria porri</Emphasis> (Ellis) Cif.) resistance,yield and earliness in tropical onions (<Emphasis Type="Italic">Allium cepa</Emphasis> L.)

Five open pollinated onion cultivars Red Creole, Kaharda, Koumassa, Sokoto local and Ori were crossed in a complete diallel and their progenies were evaluated in replicated trials, at Sokoto and Talata Mafara, Nigeria, during the 2004/2005 and 2005/2006 seasons. The experiments were randomised as complete block design with three replications. 30 mls of 10⁻¹ cfu of spore suspension of Alternaria porri prepared by serial dilution was poured into the centre of each plot (sunken bed) immediately after irrigation at 2 weeks after transplanting. Combined analysis across seasons and locations indicated significant (P < 0.05) differences between the populations with respect to all the characters under study. Crosses Ori × Koumassa and Koumassa × Ori recorded highly significant (P < 0.01) positive high parent heterosis for bulb diameter. Crosses Ori × Sokoto local and Ori × Koumassa recorded highly significant (P < 0.01) negative high parent heterosis for days to maturity. Cross Sokoto local × Koumassa exhibited highly significant (P < 0.01) positive high parent heterosis for number of leaves/plant. Crosses Red Creole × Kaharda and Kaharda × Red Creeole recorded highly significant (P < 0.01) positive high parent heterosis for disease incidence. Red Creole × Kaharda and Kaharda × Red Creeole also recorded highly significant (P < 0.01) positive high parent heterosis for fresh bulb yield. Cross Kaharda × Ori recorded highly significant (P < 0.01) positive high parent heterosis for bulb weight. The cross Kaharda × Sokoto local recorded significant (P < 0.05) negative high parent heterosis for days to maturity while the cross Red Creole × Kaharda recorded highly significant (P < 0.01) positive high parent heterosis for number of leaves/plant. Bulb diameter and bulb weight recorded highly significant (P < 0.01) and significant (P < 0.05) environmental correlation with days to maturity.